The Final FRCR Complete Revision Notes 3 PDF

The Final FRCR Complete Revision Notes 1 The Final FRCR Complete Revision Notes Vincent Helyar and Aidan Shaw 2 CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2018 by Taylor & Francis Group, LLC CRC Pre...

The Final FRCR Complete Revision Notes 1 The Final FRCR Complete Revision Notes Vincent Helyar and Aidan Shaw 2 CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2018 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed on acid-free paper International Standard Book Number-13: 978-1-4822-5972-8 (Paperback) 978-1-138-30686-8 (Hardback) This book contains information obtained from authentic and highly regarded sources. While all reasonable efforts have been made to publish reliable data and information, neither the author[s] nor the publisher can accept any legal responsibility or liability for any errors or omissions that may be made. 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Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com 4 Contents Foreword Acknowledgements Introduction Authors 1 Cardiothoracic and Vascular Cardiovascular Respiratory 2 Musculoskeletal General musculoskeletal Paediatrics MSK tumours 3 Gastrointestinal Gastrointestinal tract Peritoneum and mesentery Liver Pancreas Spleen Abdominal aids 4 Genitourinary, Adrenal, Obstetrics and Gynaecology and Breast Urinary tract Adrenal glands 5  Gynaecology Male genital tract Breast 5 Paediatrics Central nervous system ENT and orbits Cardiovascular Respiratory Miscellaneous Gastrointestinal Genitourinary 6 Central Nervous System, Head and Neck Trauma Cerebrovascular disease Miscellaneous central nervous system disease Basics of brain tumours Intra-axial tumours Extra-axial tumours Congenital intracerebral lesions CNS infection Demyelinating disease Leukodystrophy Metabolic disorders Degenerative disorders Head and neck Ear Thyroid, parathyroid and salivary glands Orbits Mandible and maxilla Spine Cord Index 6 Foreword The transition from the FRCR Part 1 to FRCR Part 2 is always a challenge. The first part of the examination demands encyclopaedic knowledge of several subjects. Although understanding is important, there is no getting away from the fact that in order to pass this examination a candidate needs to extensively read and absorb many details. Part 2 is very different—although wide reading and extensive knowledge would help, this examination is mainly a test of a candidate’s ability to use his or her knowledge to make appropriate clinical diagnoses and management decisions. Many candidates find it difficult to switch from ‘MCQ mode’ to the pragmatic and sensible approach required for the second part of the FRCR examination. Although there is no substitute for clinical practice for making this necessary transition, this excellent book by Dr. Aidan Shaw and Dr. Vincent Helyar will help FRCR Part 2 candidates to focus on real clinical issues in a sensible way and to think like practising radiologists in real clinical situations. It adopts a succinct, accessible style peppered with the kind of pertinent points which trainees usually only pick up as they move through a sub-specialty. Plain radiographs and cross-sectional imaging examinations of excellent quality are annotated clearly and are accompanied by the main differential diagnoses presented in a format that is easy to read and memorise. I anticipate that the book will be used as an adjunct to major textbooks for the purposes of revision, and as a self-testing aid as the examination 7 approaches. It is enjoyable to read and easy to use, and its authors can take pride in a challenging task extremely well accomplished. Andreas Adam, CBE 8  Professor of Interventional Radiology Guy’s and St. Thomas’ NHS Foundation Trust London, UK 9 Acknowledgements I dedicate this book to my family, my wife Sinéad and my daughters Clara and Elizabeth for their love and support. I am very grateful to my parents for giving me my love of words and to my mother for the inspiration to write. 10  Vincent Helyar I would like to dedicate this book to my amazing wife Juliette and my son Edward for their continuing love, support and understanding throughout the writing of this book and my career. I would also like to thank my legendary parents, Bryn and Ozden. Without their continual love and support, I would not be where I am today. 11  Aidan Shaw 12 Introduction This book is the product of several years of hard labour, the aim being to produce a definitive revision manual for the unfortunate souls preparing for the final Fellowship of the Royal College of Radiologists (FRCR). The aim of the book is to support you in preparation both for the written ‘2a’ exams as well as the oral and written ‘2b’ component. In each topic covered in this book, we hope that you will find enough information to understand the clinical context of a condition and its key imaging characteristics. Some information that you may find particularly useful is highlighted throughout in boxes. To help you pass the 2a modules, we suggest you: 1. Over-prepare—do not underestimate how much work these exams require! 2. Start early and read widely (expect about 3 months of preparation per module if working in the evenings and occasional weekends). 3. Do as many multiple choice questions (MCQs) as you can and read up on everything you do not know. For the 2b modules, we suggest you: 1. Over-prepare. 2. Report lots of plain films. 3. Read some case study texts early on (e.g. 4–6 months pre-exam). 4. Focus on viva practice, especially in the last 2–3 months. 5. Avoid burnout—know when to have time out! 13 6. Do at least 70 dedicated rapid-reporting plain film packs. 7. Use a checklist for rapid reporting. 8. Rehearse spiels for classic cases—whether or not you use them, it will build your confidence in presenting a case. 9. Practice with your peers. The FRCR examination is a great challenge to prepare for, not least because of the sheer volume of information. You will be expected to have both a breadth and depth of knowledge, and in the dreaded final viva, you will be expected to assimilate all of this under pressured conditions in order to proffer a handful of sensible differential diagnoses—good luck! Rest assured that your hard work will pay off and you will emerge with a very robust qualification. 14 Authors Dr Vincent Helyar, FRCR EBIR is a Consultant Interventional Radiologist at Hampshire Hospitals NHS Foundation Trust. After a successful career in information technology, Vincent graduated from Guy’s, King’s and St Thomas’ School of Medicine in 2009 with Distinction. He completed his Foundation years in the South West of England and then began specialty training in Clinical Radiology at Guy’s and St Thomas’ NHS Foundation Trust. He completed specialty training in 2017 following a 2-year Fellowship in Interventional Radiology. Vincent trained as an Interventional Radiologist at Guy’s and St Thomas’ NHS Foundation Trust. His practice includes a broad range of both vascular and non-vascular intervention. He has a keen interest in teaching and has authored several book chapters, numerous articles and has presented widely at national and international conferences. He is a member of the Royal College of Radiologists, the British Society of Interventional Radiology, the European Society of Radiology and the Cardiovascular and Interventional Radiological Society of Europe. Dr Aidan Shaw, MRCS FRCR is a Consultant Interventional Radiologist at Maidstone and Tunbridge Wells NHS Trust. He completed his specialty training at Guy’s and St Thomas’ NHS Foundation Trust including a two-years Interventional Radiology fellowship. He has a particular interest in uterine artery embolisation, ovarian vein embolisation and prostate artery embolisation. 15  He has authored books as well as book chapters, has been published extensively in a number of international peer-reviewed journals and has won awards and fellowships in the field of surgery and radiology. He is a member of the Royal College of Radiologists, the Royal College of Surgeons, the British Society of Interventional Radiology and the Cardiovascular and Interventional Radiological Society of Europe. 16  CHAPTER 1 Cardiothoracic and Vascular CARDIOVASCULAR ABERRANT LEFT PULMONARY ARTERY Occurs due to the failure of formation of the sixth aortic arch. Blood to the left lung arises from an aberrant left pulmonary artery that arises from the right pulmonary artery. The vessel passes between the trachea and oesophagus and causes narrowing of the trachea in a caudal direction. Associated with other anomalies (e.g. patent ductus arteriosus). PLAIN FILM Bronchial obstruction causes lung emphysema (right lung, middle lobe, lower lobes, left upper lobe) Barium swallow Anterior indentation on the oesophagus, just above the level of the carina Aortic aneurysm Considered either true (aneurysm bound by all three walls of the vessel) or false (i.e. pseudoaneurysm, part of the wall of the aneurysm is formed by surrounding soft tissue). Aneurysms are described as being saccular or fusiform. Saccular aneurysms are eccentric in shape, the aneurysm only forming from part of the circumference of the vessel wall. Associated with mycotic aneurysms (Figure 1.1). 17  Fusiform aneurysms involve the full vessel circumference and feature cylindrical dilatation. More commonly seen with atherosclerotic aneurysms (Figure 1.2). Figure 1.1 Saccular aneurysm. CT angiogram demonstrating a saccular aneurysm arising from the abdominal aorta. 18 Figure 1.2 Fusiform aneurysm. CT angiogram demonstrating a fusiform abdominal aortic aneurysm. CT Thoracic aortic aneurysms are mostly atherosclerotic and calcified in 75%. Other causes include cystic medial necrosis (a disorder of the large arteries with formation of cyst-like lesions in the media, associated with e.g. Marfan and Ehlers–Danlos syndromes) and syphilis (expect extensive calcification). Abdominal aortic aneurysms (AAAs)—mostly atherosclerotic. Popliteal aneurysms, associated with an AAA in 30%–50%. INTERVENTION Advised when diameter >5.5 cm (the risk of rupture is greatly increased over this). Endovascular stents are generally oversized by 10%. The presence of perigraft air is a common finding in the immediate post-operative period; however, if present >1 week after surgery, suspect infection. Endoleak is defined as the continued perfusion of the aneurysm despite placement of a stent graft (Table 1.1). Table 1.1 The classification of endovascular stent graft endoleaks Type of endoleak Site Type 1 Leak from the stent/graft attachment due to an inadequate seal 1a Proximal 1b Distal Type 2 Filling of the sac from retrograde flow through aortic branches (e.g. (most lumbar arteries, inferior mesenteric) common, 80%) Type 3 Structural failure of the stent graft/leak from mid-graft component junction Type 4 Porosity of the graft (corrects with reversal of anticoagulation) Type 5 Endotension (i.e. aneurysm sac enlargement without demonstrable leak) 19 AORTIC COARCTATION Narrowing of the aortic isthmus, mostly occurs in males (80%). Associated with multiple congenital anomalies, most commonly a bicuspid aortic valve (seen in 80%). Other associations include Turner syndrome (15%–20%), posterior fossa malformations–hemangiomas–arterial anomalies–cardiac defects–eye (PHACE) syndrome and intracerebral berry aneurysms and bleeds. Causes heart failure in infancy and hypertension later. PLAIN FILM (FIGURE 1.3) Cardiomegaly with left ventricular hypertrophy. Look for the ‘reverse 3 sign,’ formed by pre-stenotic aortic dilatation, the coarctation and post-stenotic dilatation. Inferior rib notching (large collateral intercostal vessels), most commonly affecting the fourth to eighth posterior ribs after 5 years of age. Figure 1.3 Coarctation of the aorta. Chest x-ray demonstrating cardiomegaly, a reverse 3 sign (red arrow) and inferior rib notching (white arrow). 20 AORTIC DISSECTION Blood under arterial pressure enters a tear in the intima and tracks along in the media. A total of 60% of dissections involve the ascending aorta (Stanford type A and DeBakey type I and II) and will require surgical management. They mostly originate from the right anterolateral wall of the ascending aorta, just distal to the aortic valve. They are associated with connective tissue disorders (Marfan and Ehlers–Danlos syndromes), bicuspid aortic valves, coarctation, relapsing polychondritis, Behçet disease, Turner syndrome, trauma and pregnancy (Table 1.2). Table 1.2 Stanford and DeBakey classifications of thoracic aortic dissection Stanford DeBakey Type A Type I Affects the ascending aorta and/or arch and Involves ascending and descending possibly into the descending aorta aorta Type II Involves the ascending aorta only Type B Type III Affects the descending aorta and/or arch IIIA—descending aorta only without beyond the left subclavian artery extension below the diaphragm IIIB—descending aorta with extension below the diaphragm PLAIN FILM Widened mediastinum (over 8 cm) Double aortic contour Displacement of aortic knuckle calcification by 10 mm May manifest as lower lobe atelectasis CT (FIGURE 1.4) Dissection flap separating true and false lumens (can be hard to tell which is which). The false lumen tends to be larger, enhances more slowly and may be thrombosed. The ‘beak’ sign (wedges around the true lumen) and 21  ‘cobweb’ sign (remnant ribbons of media appearing as slender linear areas of low attenuation) are also clues. Figure 1.4 Aortic dissection. CT angiogram demonstrating a dissection of the ascending and descending thoracic aorta—Stanford type A and DeBakey type I. Red arrow—false lumen of the ascending aorta. White arrow—true lumen of the descending thoracic aorta. AORTIC TRANSECTION Occurs following major blunt trauma, 90% in the proximal descending aorta at the level of the isthmus (mobile aortic arch moves against the fixed descending aorta at the level of the ligamentum arteriosum). The diaphragmatic hiatus and aortic root are other risk areas. PLAIN FILM (FIGURES 1.5 AND 1.6) WIDENED MEDIASTINUM (OVER 8 CM ABOVE THE LEVEL OF THE CARINA AND MORE THAN 25% OF THE WIDTH OF THE CHEST) OR INDISTINCT ARCH CONTOUR. Left apical pleural cap is classic, due to pleural haematoma. Look for rightward deviation of the trachea and depression of the left main bronchus. 22 Figure 1.5 Transection of the aorta. Chest x-ray demonstrating widening of the mediastinum, a left apical pleural cap with slight deviation of the trachea to the right. There is also a fracture of the right second rib in keeping with high-energy trauma. Figure 1.6 Transection of the aorta. CT demonstrating a transection of the aorta (white arrow) with mediastinal haematoma and pleural haematoma (red arrow), which creates the apical pleural cap on the chest x-ray. AORTIC REGURGITATION 23 The causes are congenital (e.g. bicuspid aortic valve) or acquired. Acquired regurgitation is more common and may be divided into processes affecting the valve (e.g. rheumatic fever and endocarditis) or just the ascending aorta (e.g. syphilis, Reiter syndrome, Takayasu arteritis, etc.). PLAIN FILM Non-specific cardiomegaly with left ventricular enlargement Apex blunted and inferolateral displacement of the left heart border AZYGOS CONTINUATION OF THE INFERIOR VENA CAVA Absent hepatic segment of the inferior vena cava (IVC). Commonly associated with IVC duplication, congenital heart disease and polysplenia syndromes. Box 1.1 ANOMALIES ASSOCIATED WITH POLYSPLENIA SYNDROME Pulmonary Bi-lobed continuation of the lungs Bilateral hyparterial bronchi Cardiac Bilateral superior vena cava (SVC) Dextrocardia/cardiac malposition Anomalous pulmonary venous return Atrial septal defect/ventricular septal defect (ASD/VSD) Abdominal Small bowel malrotation Absent gallbladder Stomach malposition BEHÇET DISEASE Behçet disease is a multi-systemic immune-mediated vasculitis affecting both arteries and veins, more common (by four- to five-fold) in young women. The classic presentation is with a triad of oral ulceration, genital ulceration and ocular inflammation. CT (FIGURES 1.7 AND 1.8) CARDIOVASCULAR SYSTEM INVOLVED IN UP TO 30%. LOOK FOR AORTIC 24 PSEUDOANEURYSMS AND OCCLUSION/STENOSIS OF DISTAL VESSELS. Pulmonary artery aneurysms and haemorrhage. Figure 1.7 Behçet disease. Chest x-ray demonstrating coil embolisation of a pulmonary artery aneurysm and dense airspace opacification in keeping with haemorrhage. 25 Figure 1.8 Behçet disease. CT pulmonary angiogram (CTPA) demonstrating a right pulmonary artery aneurysm (with arrow). MRI Central nervous system (CNS) involved in up to 20%. The best indicator is a brainstem/basal ganglia lesion (bright on T2) in the right clinical context. BUERGER DISEASE Also known as thromboangiitis obliterans. It is a non-atherosclerotic vascular disease affecting medium- and small-sized vessels of the upper and lower limbs. It affects the distal vessels first and then progresses proximally. INTERVENTION Characteristic appearance on angiography of arterial occlusions with multiple corkscrew shaped collaterals. Skip lesions are also a recognised feature—occlusions with normal intervening arteries. 26 CARDIAC TRANSPLANTATION Complications post-cardiac transplantation include infection and post- transplant lymphoproliferative disorder (PTLD). INFECTION This is the most common complication following cardiac transplant. Infections in the first month post-transplant are more likely bacterial. After that, opportunistic viral and fungal infections are more common. Plain film Single or multiple pulmonary nodules may represent Nocardia or Aspergillus infection. Aspergillus is more common 2 months post-transplant. Nocardia tends to occur later (e.g. 5 months). PTLD Non-specific complication mostly occurring within 1 year of transplant. Affects about 10% of solid organ recipients. It is due to B- or T-cell proliferation, usually following Epstein–Barr virus (EBV) infection. Responds rapidly to a reduction in immunosuppression or alternatively rituximab. Plain film Single or multiple well-defined, slow-growing lung nodules Consolidation less common Hilar or mediastinal lymph node enlargement CARDIAC ANGIOSARCOMA More frequently affects middle-aged males. Typically involves the pericardium (80%) and the right atrium, which explains the presentation with right heart failure or tamponade. CT Diffusely infiltrating mass extending along the pericardium and extending into the cardiac chambers/pericardiac structures Or, a 27  low-attenuation mass in the right atrium showing heterogeneous enhancement and central necrosis Cardiac lipoma This is the second most common benign cardiac tumour of adulthood, usually discovered incidentally. They can grow to a large size without causing symptoms. CT Homogeneous low-attenuation mass in the pericardium or a cardiac chamber Cardiac metastases Most commonly from lung, breast or melanoma. CARDIAC MYXOMA This is the most common primary cardiac tumour of adulthood. It is typically found in the left atrium (75%–80%). Associated with the Carney complex (a rare multiple endocrine syndrome featuring multiple cardiac myxomas and skin pigmentation). ECHOCARDIOGRAPHY Mobile echogenic mass with a well-defined stalk—may obstruct the mitral valve Plain film/CT Cardiomegaly with left atrial enlargement (splaying of the carina) Signs of mitral valve obstruction (pulmonary hypertension and pulmonary oedema from increased left atrial pressure) Soft tissue mass within the left atrium (Figure 1.9) 28 Figure 1.9 Atrial myxoma. CT image demonstrating a soft tissue mass within the left atrium; this was proven to be an atrial myxoma. CARDIAC RHABDOMYOMA Most common childhood cardiac tumour, mostly diagnosed incidentally (usually asymptomatic) at 12–15 mm, commonly located at the base of the interventricular septum) leads to narrowing of the outflow tract. Affects flow dynamics and gives rise to systolic anterior motion of the mitral valve. MRI Useful for assessing the distribution of disease and wall thickness. Note—fibrotic tissue within the interventricular septum leads to patchy, delayed enhancement post-contrast. RESTRICTIVE CARDIOMYOPATHY Any disease that restricts diastolic filling—restrictive cardiomyopathy is a diastolic problem, so atria are large and ventricles small. Causes include sarcoidosis, amyloidosis and haemochromatosis. TAKOTSUBO CARDIOMYOPATHY Transient cardiac syndrome predominantly involving postmenopausal women (90%). There is left ventricular apical akinesis and dysfunction, with normal coronary arteries. The typical presentation is with chest pain that mimics a myocardial infarction (troponin enzymes are mildly elevated) following a physically/emotionally stressful event. Plain film 30  Pulmonary oedema MRI Left ventricular dyskinesia and ballooning High T2 signal (oedema) in the ventricular wall No significant delayed contrast enhancement of the ventricular wall (distinguishing from myocardial infarction) Carotid artery stenosis Box 1.2 CAROTID ARTERY STENTING There are specific indications for carotid artery stenting (rather than endarterectomy; e.g. restenosis following surgery, radiation stenosis and previous neck surgery on the ipsilateral side). Stent is placed within 2 weeks of a stroke. This is a major cause of stroke, typically caused by atherosclerosis at the carotid bulb and the proximal segment of the internal carotid artery. Note that the internal carotid artery is also the second most common site for fibromuscular dysplasia stenosis after the kidneys. DOPPLER ULTRASOUND (US) More than 70% stenosis increases systolic and diastolic flow velocity. Systolic flow >230 cm/second and diastolic flow >110 cm/second are significant. MYOCARDIAL ISCHAEMIA HIBERNATING MYOCARDIUM This is viable myocardial tissue that has adapted over time to reduced perfusion. The tissue may be a target for revascularisation. Nuclear medicine Abnormal perfusion and abnormal wall motion MYOCARDIAL INFARCTION Nuclear medicine Matched rest and stress perfusion defect, does not normalise. 31  Note: Myocardial ischaemia shows a perfusion abnormality that reverses on rest. MRI Infarcted tissue is indicated by delayed hyper-enhancement. In the first few days after infarction, there is high T2 signal in the affected myocardium. STUNNED MYOCARDIUM Temporary, acute severe ischaemia causes an abnormality of wall motion. Nuclear medicine Normal perfusion, abnormal wall motion. Repeated stunning may cause myocardial hibernation. PERICARDIAL CYST Mostly an incidental finding, typically found at the right anterior cardiophrenic angle. PLAIN FILM (FIGURE 1.10) Well-demarcated, rounded mass at right cardiophrenic angle. 32 Figure 1.10 Pericardial cyst. Chest x-ray demonstrating a well-demarcated mass at the right cardiophrenic angle. CT (FIGURE 1.11) Low-attenuation (Hounsfield unit [HU25]) rounded mass adjacent to the pericardium 33 Figure 1.11 Pericardial cyst. Computed tomography image demonstrating a low-attenuation mass adjacent to the pericardium. MRI Low T1 signal, high on T2 PERICARDITIS Most pericarditis is idiopathic and may be due to an undiagnosed viral infection. Restrictive pericarditis is associated with myocardial thickening. ACUTE PERICARDITIS Look for evidence of a pericardial effusion. Symptoms (cardiac tamponade) relate to both the volume of the effusion and speed of accumulation. Plain film Normal until fluid volume >250 mL. Bilateral hila overlay sign, globular enlargement of the heart (gives a ‘water bottle’ appearance). On a lateral chest x-ray, the signs are the epicardial fat pad sign (epicardial fat separated from pericardial fat by a lucent line) and filling in of the retrosternal space. 34 CONSTRICTIVE PERICARDITIS Thickened pericardium restricts diastolic ventricular filling, and the end result is cardiac failure. The aetiology includes sarcoidosis, tuberculosis (TB), chronic renal failure, rheumatic fever, trauma and radiation. Plain film Pericardial calcification (50%) and pleural effusions Pericardial effusion No pulmonary oedema CT Pericardial thickening >4 mm suggests pericarditis (normal 2 mm, excludes pericarditis). Pericardial effusion. Findings may be isolated to one side of the heart. Pericardial enhancement with contrast. MRI Useful for distinguishing pericardial thickening from pericardial effusion. POLYARTERITIS NODOSA This is a vasculitis of the small- and medium-sized arteries and is more common in males. Fever, malaise and weight loss are almost always present, due to ischaemic complications. Most (80%) have renal involvement. The gastrointestinal (GI) tract is affected in about 60%. CT/INTERVENTION (FIGURES 1.12 AND 1.13) 1–5-MM MICROANEURYSMS, TYPICALLY PERIPHERAL AND INTRA- RENAL. Aneurysms tend to occur where vessels bifurcate. Stenoses also occur. Vasculitis causes distal ischaemia (renal infarcts, gut ischaemia, etc.). May present with haemorrhage. 35 Figure 1.12 Polyarteritis nodosa. Left renal artery angiogram demonstrating multiple small renal artery aneurysms (white arrow). 36 Figure 1.13 Polyarteritis nodosa. Inferior mesenteric artery angiogram demonstrating multiple small aneurysms (white arrows). POPLITEAL ARTERY ENTRAPMENT SYNDROME Symptomatic deviation and compression of the popliteal artery secondary to an abnormal relationship with the medial head of gastrocnemius/popliteus (rare). Affects young sportsmen and is bilateral in up to two-thirds. May present as intermittent claudication or acute thrombosis. The management is surgical. MRI Most useful for demonstrating artery–muscle relationship and vessel lumen. INTERVENTION 37  Medial deviation or compression of the artery on plantar or dorsi flexion of the ankle. POST-EMBOLISATION SYNDROME This arises as a complication of transarterial chemoembolisation or arterial embolisation (e.g. liver lesion treatment or uterine artery embolisation). Incidence increases with increasing lesion size. It usually occurs within the first 3 days and eases over the next 3 days, and is usually self-limiting. The symptoms are mild fever, nausea/vomiting and pain. CT Commonly demonstrates gas within the embolised lesion—does not imply infection. RENAL ARTERY STENOSIS Accounts for 200 cm/second. Damped systolic waveform (‘parvus–tardus’). Affected side may show an elevated resistive index if measured proximal to the stenosis. INTERVENTION Focal or segmental stenosis, atherosclerotic lesions tend to be at the ostium or proximal 2 cm. Angioplasty effective in 80% for proximal lesions, 30% for ostial lesions. RHEUMATIC HEART DISEASE 38 Heart disease arising from rheumatic fever (a complication of a streptococcal pharyngitis). May affect the myocardium, pericardium or valves (mitral valve affected most often). PLAIN FILM Enlarged left atrial appendage/left atrium is classic (splaying of the carina with left atrial enlargement). Mitral stenosis—look for evidence of pulmonary oedema, left atrial enlargement, alveolar haemorrhage and pulmonary ossification (due to pulmonary haemosiderosis). Mitral regurgitation—look for left ventricular enlargement. Also look for pericardial calcification, valvular calcification and global cardiomegaly. SARCOIDOSIS Suspected in patients with sarcoidosis and arrhythmias, affects about 5% of sarcoidosis patients. Associated with poorer outcomes and up to a quarter of deaths from sarcoidosis. MRI In acute sarcoidosis, there may be delayed enhancement (also with ischaemia) or T2 hyperintense nodules at the base of the septum and left ventricle. Look for high T2 signal in the epicardium with or without wall thickening secondary to oedema; subendocardium is spared. Pericardial effusion. SUBCLAVIAN STEAL SYNDROME Severe stenosis of the proximal subclavian artery causes retrograde flow in the ipsilateral vertebral artery (to bypass the stenosis by collaterals). In partial steal, there is antegrade flow in the vertebral artery in systole, with retrograde flow in diastole. Associated with cerebral ischaemic symptoms (e.g. vertigo, dizziness and syncope). Mostly due to atherosclerosis, but also linked to vasculitis. Mostly occurs on the left. 39 US Retrograde ipsilateral vertebral artery flow with evidence of a subclavian stenosis (parvus–tardus and monophasic waveform in the distal subclavian artery) CT/mR angiography Subclavian stenosis/occlusion Delayed enhancement/retrograde flow in ipsilateral vertebral artery INTERVENTION Angioplasty and stenting preferred to surgical bypass in symptomatic patients Takayasu arteritis This is a large-vessel arteritis tending to affect young women. There is granulomatous inflammation of the vessel wall, with vessels ultimately becoming stenotic, occluded or aneurysmal. CT Vessel wall thickening and enhancement. Aorta (thoracic particularly) and its branches are mostly affected. Pulmonary arteries affected in 50%, peripheral pulmonary arteries may be ‘pruned’, trunk dilated. Vessels calcify in chronic disease (otherwise they are more likely to become aneurysmal). MRI Look for high signal on the short tau inversion recovery (STIR) in the vessel wall, indicating oedema. RESPIRATORY ADULT RESPIRATORY DISTRESS SYNDROME (ARDS) Box 1.3 THE BASIC PRINCIPLES OF HRCT OF THE THORAX Why? HRCT of the chest is the only way to demonstrate the secondary pulmonary lobule (i.e. the basic anatomical structure responsible for gas exchange composed of acini, bronchioles, lymphatics and vessels). 40 When? Any diffuse lung disease including interstitial lung disease, pulmonary eosinophilias and obstructive lung disease and to investigate patients with symptoms and a normal chest x- ray. How? The key aspects of HRCT are thin collimation (1–2-mm slices) and high spatial resolution reconstruction. Slices may be taken at staggered intervals (‘interspaced’; e.g. six to eight images total) or as a volumetric dataset (e.g. every 10 mm)—the merits of each are debatable. Patients are usually scanned supine; prone positioning is useful to differentiate disease from ‘dependent’ changes (i.e. atelectasis in older patients and smokers). Images are usually gathered in full inspiration. Expiratory scans are used to demonstrate air- trapping or to differentiate between vascular and airway disease as a cause of air-trapping. Read more: Kazerooni, E. 2001. High-resolution CT of the lungs. American Journal of Roentgenology 177:501–519. Box 1.4 WHAT IS GROUND-GLASS ATTENUATION? An amorphous increase in lung attenuation that does not obscure vessels. Vessels are obscured by consolidation. Also known as ‘acute respiratory distress syndrome’, this is an acute condition characterised by bilateral pulmonary infiltrates and severe hypoxaemia in the absence of cardiogenic pulmonary oedema. The underlying problem is diffuse alveolar damage. PLAIN FILM Normal for the first 24 hours, then septal lines and peribronchial cuffing, but no effusions. Unlike pulmonary oedema, infiltrates are initially peripheral rather than central, and air bronchograms are more commonly seen. May be complicated by pneumonia. HIGH-RESOLUTION CT (HRCT) After months, the consolidative pattern gives way to reticulation in the non-dependent lung and, finally, honeycombing. α1 ANTITRYPSIN DEFICIENCY 41 α1 antitrypsin is an inhibitor of a protease for elastin. The deficiency is also associated with cirrhosis, necrotising panniculitis and Wegener granulomatosis. It causes a pan-lobar emphysema in the lungs in young patients (aged 40–50 years). PLAIN FILM (FIGURE 1.14) Normal in mild disease Later on, lucent, hyperinflated lungs in a young patient Figure 1.14 α1 antitrypsin deficiency. Chest x-ray demonstrating hyperexpanded lungs and predominant lower zone emphysema. HRCT (FIGURE 1.15) Pan-lobular emphysema (i.e. enlarged and destroyed secondary pulmonary lobule) tending to affect the lower lobes bilaterally Associated with bronchiectasis 42 Figure 1.15 α1 antitrypsin deficiency. Computed tomography image demonstrating marked pan-lobular emphysema. AMIODARONE LUNG DISEASE Box 1.5 DIFFERENTIALS FOR A HYPERDENSE LIVER Amiodarone Gold Thorotrast (old contrast agent) Haemochromatosis Haemsiderosis (spleen affected, too) Glycogen storage disease An interstitial lung disease affecting patients after amiodarone treatment. It occurs 1–12 months following at least 6 months of treatment. HRCT Peripheral, hyperdense consolidation and patchy ground-glass opacification (i.e. alveolar infiltrates) Peripheral/basal fibrosis Hyperdense liver and heart—this is classic 43 ARTERIOVENOUS MALFORMATION (AVM) Affects up to 15% of people with hereditary haemorrhagic telangiectasia (Osler–Weber–Rendu syndrome). Patients may present with orthodeoxia (postural hypoxaemia accompanied by breathlessness) or stroke due to paradoxical emboli. PLAIN FILM/CT Well-defined, lobulated nodules with a feeding artery and draining vein May contain phleboliths Most are unilateral and two-thirds are in the lower lobes. ASBESTOS-RELATED LUNG DISEASE Box 1.6 CAUSES OF LOWER ZONE FIBROSIS Asbestosis Connective tissue diseases (rheumatoid, scleroderma and systemic lupus erythematosus) Idiopathic pulmonary fibrosis (usual interstitial pneumonia [UIP]) Drugs (methotrexate, bisulfan and bleomycin) Look for soft tissue calcification, dilated oesophagus, distal clavicular osteolysis, pleural plaques, diaphragmatic calcification and sympathectomy clips to help diagnose the cause. This refers to a spectrum of lung disease resulting from asbestos exposure. It may be a benign pleural disease, usually occurring >20 years after exposure. More common in males (occupational). PLAIN FILM Pleural effusion first. Then, often (80%) pleural plaques affecting both parietal pleura (posterolateral/lateral/costophrenic angles/mediastinal). Diaphragmatic plaques are pathognomonic, the apices are spared. Plaques are not always calcified. CT (FIGURE 1.16) Look for areas of round atelectasis (‘pseudotumour’ appearance) next to a pleural plaque. The bronchovascular bundle typically converges 44  into the lesion (‘comet tail’ sign). Figure 1.16 Rounded atelectasis. CT images demonstrating calcified pleural plaques with rounded atelectasis (pseudotumour; red arrow) overlying a calcified pleural plaque (white arrow). The bronchovascular bundles form the comet tail sign (red arrow). ASBESTOSIS This is an interstitial lung disease due to asbestos exposure. There is progressive dyspnoea and a strong association with malignancy (adenocarcinoma more likely). Plain film Lower zone fibrosis (due to inhalation gradient) Pleural plaques Effusions HRCT Initially small, sub-pleural, round or branching opacities a few millimetres from the pleura—this is peri-bronchiolar fibrosis. Sub-pleural curvilinear opacities, parallel to the chest wall—may represent atelectasis or be associated with honeycombing later on. Late disease is characterised by parenchymal bands and reticulation with distortion of the lung parenchyma and traction bronchiectasis. As the disease progresses, there is basal honeycombing, appearing similar to UIP. No lymph node enlargement. 45 ASPERGILLOSIS Aspergillosis refers to a spectrum of abnormalities caused by infection with the Aspergillus fungus. The severity of the disease depends partly on the patient’s immune status (Note: AIDS alone does not count). ASPERGILLOMA Affects patients with normal immunity but abnormal lungs. Fungal infection occurs within a pre-existing cyst, cavity, bulla or area of bronchiectasis. Commonly referred to as mycetoma. Plain film (Figure 1.17) Typically upper lobe abnormality, mass within a cavity frequently accompanied by pleural thickening. ‘Monad’/air crescent sign—the fungus ball is frequently surrounded by a crescent of air. Figure 1.17 Cystic fibrosis with aspergilloma. Chest x-ray demonstrating a right upper zone cavity with a soft tissue focus outlined by a crescent of air (Monad sign; white arrow) in 46 keeping with an aspergilloma. A further aspergilloma is identified within the left mid-zone (red arrow). CT Fungus ball (may calcify) lying dependently within a cavity or thin- walled cyst. Intervention Bronchial arteries supplying the abnormal lung become hypertrophied and are liable to bleed. Bronchial artery embolisation may be performed for haemoptysis. ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS (ABPA) Usually occurs in the context of chronic asthma or cystic fibrosis. Aspergillus organisms are inhaled by an atopic host and cause a hypersensitivity reaction. It is the most common pulmonary cause of an eosinophilia. Treatment is with steroids. Plain film (Figure 1.18) Migratory patchy foci of consolidation. ‘Tram track’ appearance (i.e. gross bronchiectasis), central/upper zones is classic. Tubular opacities are classic—these are dilated airways plugged with mucous, known as the ‘finger in glove’ appearance. Atelectasis from airway obstruction. 47 Figure 1.18 Allergic bronchopulmonary aspergillosis. Chest x-ray demonstrating gross central bronchiectasis with tubular opacities. These represent mucous-filled bronchi known as the ‘finger in glove’ appearance. HRCT (Figure 1.19) Hyperdense mucoid impaction of central and upper lobe airways giving rise to bronchiectasis. Bronchiectasis is varicose or saccular. Centrilobular nodules and masses are features, not pleural effusions. Chronic disease leads to upper zone fibrosis. Air-trapping—gives a mosaic pattern of attenuation. 48 Figure 1.19 Allergic bronchopulmonary aspergillosis. CT image demonstrating gross central varicose bronchiectasis (white arrow) with mucous-filled bronchi. SEMI-INVASIVE PULMONARY ASPERGILLOSIS Also known as ‘chronic necrotising pulmonary aspergillosis’. It may affect those with mild immunosuppression; overall prognosis is good. Treatment is with anti-fungals. CT Typically upper zone nodules that then cavitate—a necrotic area then separates the nodule from the surrounding lung (the ‘air crescent’ sign). ANGIOINVASIVE ASPERGILLOSIS The most common fungal infection to affect the severely immunosuppressed (commonly post-transplant, leukaemia and post- chemotherapy). Invades blood vessels and causes pulmonary infarction. Rapid progression and high mortality. CT 49  Nodules with a rim of ground-glass opacification (haemorrhage)— known as the ‘halo’ sign Airway-invasive aspergillosis Aspergillosis that affects the airways. It may manifest as acute tracheobronchitis, bronchiolitis or bronchopneumonia. There is ulceration of the airways. CT Nodular opacities, centrilobular nodules or consolidation ASPIRATION Location depends on the position of the patient at the time of aspiration. The left lung may be spared. PLAIN FILM Most commonly the lower lobes are affected if erect; posterior upper lobe and superior lower lobe are affected if supine. CT Consolidation, material in the airway May be complicated by necrosis or abscess formation BRONCHIECTASIS Box 1.7 CAUSES OF BRONCHIECTASIS Idiopathic Most common cause overall Congenital Cystic fibrosis—most commonly congenital Bronchial atresia Primary ciliary dyskinesia Acquired Post-infectious (including ABPA)—most commonly acquired Aspiration (including foreign body obstruction) Inflammation—rheumatoid, sarcoid 50 Defined as abnormal, irreversible airway dilatation often associated with thickening of the bronchial wall. Subtypes are cylindrical, varicose and cystic. CYLINDRICAL Relatively uniform, mild airway dilatation with parallel bronchial walls. Most common and least severe. Causes include cystic fibrosis (pan-lobar), hypogammaglobulinaemia (lower lobe) and Japanese pan-bronchiolitis (pan-lobar). Plain film Tram-track appearance (en face dilated airways) or ring shadows (axial appearance of dilated airways) Bronchial wall thickening HRCT ‘Signet ring’ sign describes the axial view of a dilated airway of larger diameter than the accompanying artery. Airways do not taper as they approach the lung periphery (airways can be seen in the peripheral third of lung). VARICOSE Bronchial lumen assumes a beaded (‘string of pearls’) configuration with sequential dilatation and constriction. Causes include ABPA. Plain film Beaded airway dilatation with or without mucous impaction (‘finger in glove’). ABPA tends to affect the upper lobes. CYSTIC A string or cluster of cyst-like bronchi, the most severe kind of bronchiectasis. Causes include post-infectious (e.g. pertussis and unilobar), post-obstruction and Mounier–Kuhn syndrome. Plain film/HRCT (Figure 1.20) Cysts in clusters or strings 51  Air-fluid levels commonly seen within the cysts Figure 1.20 Cystic bronchiectasis. Chest x-ray demonstrating ring shadows in keeping with cystic bronchiectasis. BRONCHIOLITIS OBLITERANS Box 1.8 MOSAIC PERFUSION OF THE LUNG Subtle pattern of variable lung attenuation with a slight decrease in the calibre and number of pulmonary vessels within the areas of low attenuation. Expiratory HRCT differentiates between the two causes (i.e. small airways disease vs. pulmonary vascular abnormalities). Bronchiolar and peribronchiolar inflammation of the bronchioles leads to submucosal and peribronchiolar fibrosis. This causes an obstruction of the bronchial lumen, also known as obliterative bronchiolitis. Associated with transplantation (e.g. bone marrow/graft vs. host—up to 10%; lung transplant), viral infection (known as Swyer–James or MacLeod syndrome in children), toxin inhalation, rheumatoid arthritis, inflammatory bowel disease and drug reactions (bleomycin, gold, cyclophosphamide, methotrexate and amiodarone). 52 HRCT Air-trapping on expiratory scans (i.e. mosaic perfusion pattern)—this is classic and due to obstruction of the small airways. Bronchiectasis (i.e. dilated and thick-walled). Centrilobular ground-glass opacification. BRONCHOGENIC CYST This is the most common foregut malformation in the thorax. It constitutes up to 20% of mediastinal masses. It is an abnormality of the ventral diverticulum of the primitive foregut and is associated with other congenital anomalies, spina bifida, extra-lobar sequestration and congenital lobar emphysema. Box 1.9 CAUSES OF A MIDDLE MEDIASTINAL MASS Look for: Widened paratracheal stripe Mass in the aortopulmonary window Displacement of the azygo-oesophageal line Common differentials include: 1. Foregut duplication cyst (bronchogenic or oesophageal)—most common 2. Lymph node 3. Lung cancer 4. Aortic aneurysm PLAIN FILM Posterior or middle mediastinal mass, typically subcarinal and more common on the right Can be intrapulmonary—most commonly located in the medial lower lobes CT Well-circumscribed spherical mass, usually with an internal density of 0–25 HU (may be higher) May contain an air–fluid level if communicating with an airway Rim-enhancement may be seen, calcification is not typical 53 BRONCHOPLEURAL FISTULA This is an abnormal communication between the pleural space and the bronchial tree caused by lobectomy, pneumonectomy, lung necrosis, TB, etc. PLAIN FILM The pleural cavity is expected to fill with fluid post-pneumonectomy— a fistula is suspected if this does not occur, if there is an abrupt decrease in the air–fluid level or there is a new gas in a previously fluid-filled pleural cavity. Contralateral shift of the mediastinum. NUCLEAR MEDICINE Xenon ventilation study will show activity in the pleural space. CARCINOID TUMOUR (FIGURE 1.21) Carcinoid tumours are neuroendocrine tumours with low malignant potential; overall prognosis is good. They are associated with multiple endocrine neoplasia type-1. They are well-vascularised, endobronchial lesions, so commonly present with haemoptysis. Cough and recurrent pneumonia are also common. Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia—may be a precursor to a bronchial carcinoid. Characterised by small lung nodules, air-trapping, ground-glass opacification and bronchiectasis. 54 Figure 1.21 Carcinoid tumour. CT image demonstrating an avidly enhancing central mass with foci of calcification. PLAIN FILM Atelectasis commonly, a nodule (typically perihilar) may be seen. CT Avidly arterial enhancing endobronchial lesion. Rounded appearance and mostly found centrally (20% are peripheral). A third calcify, no fat content and rarely cavitate. Check lymph nodes for evidence of metastasis—Note: Lymph nodes may be enlarged from concurrent infection. NUCLEAR MEDICINE Cold on fludeoxyglucose positron emission tomography (PET). Gallium 68 PET is used to stage carcinoid. Box 1.10 A DIFFERENTIAL FOR ENHANCING LYMPH NODES Benign 55  Castleman disease Sarcoid Neoplastic Renal cell carcinoma Thyroid Small-cell carcinoma CASTLEMAN DISEASE Benign B-cell lymphoproliferation, more common in patients with HIV or AIDS. CT Multiple, enhancing lymph nodes—usually axillary or supraclavicular Mediastinal or hilar nodes—rare Centrilobular lung nodules and ground-glass opacification that mimics lymphocytic interstitial pneumonia (LIP)—rare Churg–Strauss syndrome Also known as eosinophilic granulomatosis with polyangiitis, this is a variant of polyarteritis nodosa affecting small to medium vessels. It is a necrotising vasculitis. Almost all patients have asthma, and eosinophilia and p-ANCA is positive in 75%. Cardiac involvement (including infarction) is common. Diagnostic criteria (four required): asthma, eosinophilia, neuropathy, migratory or transient pulmonary opacities, paranasal sinus abnormalities and/or extravascular eosinophils at biopsy. PLAIN FILM Transient peripheral consolidation and small pleural effusions HRCT Non-segmental, transient peripheral consolidation/ground glass Interlobular thickening Centrilobular nodules (less commonly) CYSTIC FIBROSIS This is an autosomal recessive defect in the gene regulating chloride transport, resulting in thick secretions. The lungs and pancreas are affected 56 most severely. PLAIN FILM (FIGURE 1.22) Bronchiectasis (cylindrical at first). Bronchial wall thickening. Hyperinflation (due to air-trapping). Any part of the lungs may be affected, but particularly central zones, upper lobes and apical lower lobes. Look for mucous impaction with atelectasis. Spontaneous pneumothorax. Pulmonary artery enlargement. Figure 1.22 Cystic fibrosis. Chest x-ray demonstrating hyperexpanded lungs with upper zone fibrosis, bronchial wall thickening and bronchiectasis affecting the central and upper zones. There is a cavity with a soft tissue focus outlined by a crescent of air (Monad sign; white arrow) in keeping with an aspergilloma. HRCT Most sensitive for detecting early change DIAPHRAGMATIC RUPTURE 57 Usually occurs due to blunt abdominal trauma, with the left side three-times more likely to rupture (the liver shields the right side). PLAIN FILM Abnormal contour to the diaphragm, abdominal contents in the chest and deviation of an enteral tube CT Discontinuity of the left hemidiaphragm. ‘Collar’ sign describes a focal constriction of the herniating viscera at the site of rupture. The ‘dependent viscera’ sign is where abdominal viscera lie dependently against the posterior ribs due to loss of diaphragmatic support. EXTRINSIC ALLERGIC ALVEOLITIS See ‘Hypersensitivity pneumonitis’ section. EMPHYSEMA Defined as abnormal, permanent enlargement of the airspaces distal to the terminal bronchiole, accompanied by destruction of their walls without obvious fibrosis. CENTRILOBULAR This is the most common subtype, mostly caused by smoking. Plain film Normal unless advanced Hyperinflated lucent lungs and flattened diaphragms More common in the upper zones Check for bullae HRCT Multiple small, round foci of abnormally low attenuation without visible walls that are scattered throughout normal-appearing lung parenchyma Pan-lobular Associated with various causes, including α1-antitrypsin deficiency and drug reaction (e.g. Ritalin and intravenous drug users). 58 Plain film Insensitive—look for diffuse simplification of the lung architecture. HRCT Diffusely low-attenuation lungs without clear demarcation of normal lung Loss of vascular markings PARASEPTAL Lucent, cystic spaces arranged beneath the pleural surfaces, including the interlobar fissures. Associated mostly with smoking. Plain film Rarely detectable May be complicated by pneumothorax HRCT Cystic spaces arranged beneath the pleural surfaces including the interlobar fissures. The borders of the secondary pulmonary lobule are intact. EOSINOPHILIC LUNG DISEASE Idiopathic subtypes are described below: namely, simple pulmonary eosinophilia, acute, chronic and hypereosinophilic syndrome. SIMPLE PULMONARY EOSINOPHILIA (LÖFFLER SYNDROME) Initially described as due to parasitic infection, may be associated with other pathology (e.g. ABPA) or drug reaction. It is benign and self-limiting. There is mild blood eosinophilia. Plain film ‘Reverse bat’s wing’ appearance is classic (i.e. bilateral peripheral airspace opacification). HRCT Peripheral ground-glass opacification/consolidation Nodules with surrounding ground-glass opacity (‘halo’ sign) 59 ACUTE EOSINOPHILIC PNEUMONIA Mean age of onset about 30 years, may be smoking related. Rapid onset of symptoms, fever and hypoxaemia. Marked eosinophilia on bronchoalveolar lavage (BAL)/pleural samples, but normal blood levels. Rapid response to steroids. Plain film Bilateral densities with effusions, with or without consolidation HRCT Bilateral, patchy, ground-glass opacities Interlobular septal thickening and pleural effusions CHRONIC EOSINOPHILIC PNEUMONIA Insidious onset of night sweats, pyrexia, cough and weight loss. More common in middle age and 50% have asthma. Mild blood eosinophilia and high eosinophilia on BAL. Responds to steroids. Plain film Bilateral, non-segmental, upper peripheral lobe airspace opacification (so-called ‘photographic negative of pulmonary oedema’ or ‘reverse bat’s wing’ appearance) Box 1.11 Causes of the bat’s wing appearance Simple pulmonary eosinophilia Chronic eosinophilic pneumonia Cryptogenic organising pneumonia Pulmonary vasculitis Pulmonary infarction Pulmonary contusion HRCT Dense peripheral consolidation With or without ground glass, nodules and reticulation Rarely effusions IDIOPATHIC HYPEREOSINOPHILIC SYNDROME 60 Rare condition with marked eosinophilia and end-organ eosinophilic infiltration and damage. Heart (endocardial fibrosis, cardiomyopathy, etc.) and nervous system most affected. Plain film Non-specific findings—multiple opacities, usually related to pulmonary oedema HRCT Nodules with a ground-glass halo Pleural effusions due to cardiac failure FAT EMBOLUS Lung embolus of fat-containing material (may also travel to the brain or skin), the vast majority are in patients 1–2 days following severe trauma or long bone fracture. Resolves in 1–4 weeks, often asymptomatic. PLAIN FILM/CT Bilateral, widespread, ill-defined peripheral infiltrates similar to ARDS in a patient with a recent history of major trauma Fibrosing mediastinitis Non-malignant proliferation of fibrous tissue affecting the mediastinum. Wide range of causes including infectious (histoplasmosis and TB), inflammatory (retroperitoneal fibrosis and orbital pseudotumour) and iatrogenic (radiotherapy and drug reaction). Tends to affect the young. Described as focal (80%—usually secondary to TB or histoplasmosis) or diffuse (20%—mostly inflammatory). It is the most common benign cause of SVC obstruction. FOCAL CT 2–5-cm calcified (80% calcified) mass compressing pulmonary vasculature leading to right heart strain Peribronchial cuffing, septal thickening and wedge-shaped areas of pulmonary infarction Diffuse form CT 61  Soft tissue encasement of mediastinal structures with infiltration of fat planes Fleischner Society guidelines for pulmonary nodules The purpose of the guidelines is to help with the management of small lung nodules detected incidentally. The likelihood of malignancy depends on nodule size and patient factors. A low-risk patient has minimal/no smoking history and no other known risk factors (e.g. significant family history, asbestos exposure, etc.). The likelihood of malignancy is thought to be 0.2% for nodules of 4–6 6 months, then 18–24 months 12 months >6–8 6–12 months, then 18–24 months 3–6 months, 9–12 and 24 months >8 3, 9 and 24 months + positron emission Same as low risk tomography ± biopsy Solid nodules: McMahon, H. et al. 2005. Guidelines for management of small pulmonary nodules detected on CT scans: A statement from the Fleischner Society. Radiology 237:395–400. Sub-solid nodules: Naidich, D. et al. 2012. Recommendations for the management of subsolid pulmonary nodules detected at CT: A statement from the Fleischner Society. Radiology 266:304–317. Box 1.12 A DIFFERENTIAL FOR SOLITARY PULMONARY NODULES Granuloma 62 Organising pneumonia Bronchogenic cyst Infection/inflammation Tumour Carcinoid Hamartoma GOODPASTURE SYNDROME Autoimmune disease characterised by glomerulonephritis and pulmonary haemorrhage—note that pulmonary features occur before renal manifestations. The pathology is antiglomerular basement membrane antibodies; these attack the alveolar basement membrane in the lung. Associated with a positive p-ANCA (anti-neutrophil cytoplasmic antibody) or c-ANCA in about 30%. PLAIN FILM Bilateral consolidation with sparing of the costophrenic angles and lung periphery. Progression to an interstitial/fibrotic pattern in chronic disease. HRCT Patchy ground-glass opacification with peripheral and costophrenic angle sparing. Airspace disease clears within a couple of weeks. Pulmonary fibrosis may develop in the long term. HAMARTOMA This is a common, benign lung neoplasm peaking in the sixth decade. A minority (10%) are endobronchial. PLAIN FILM Smooth, marginated nodule, frequently calcified. Two-thirds in the lung periphery. Look for atelectasis/consolidation, suggesting an endobronchial lesion. CT Fat attenuation of the nodule (50%) Or a combination of fat and calcification 63  Diffuse popcorn calcification (classic) NUCLEAR MEDICINE Note: Up to 20% are hot on PET HEREDITARY HAEMORRHAGIC TELANGIECTASIA Also known as Osler–Weber–Rendu syndrome. It is an autosomal dominant disorder characterised by multiple AVMs with a classic triad of telangiectasia, epistaxis and a positive family history. A total of 20% of patients have multiple pulmonary AVMs, causing cyanosis, dyspnoea, stroke and brain abscess. Other sites of AVMs include the brain, spinal cord, GI tract and liver. PLAIN FILM/CT Rounded/lobulated nodule with feeding vessels HISTOPLASMOSIS Fungal infection from North America and inhaled from bird and bat faeces. In immunocompetent individuals, infection almost always resolves without treatment. PLAIN FILM/CT Calcified pulmonary nodules 2–5 mm in size (miliary appearance). Enlarged lymph nodes with peripheral ‘egg shell’ calcification is classic. Look for a broncholith—this is a calcified lymph node that has eroded into the airway. Box 1.13 CAUSES OF CALCIFIED LYMPH NODES IN THE THORAX The six ‘osis’s’ Silicosis Sarcoidosis Histoplasmosis Amyloidosis Coal worker’s pneumoconiosis 64 Blastomycosis Treated lymphoma HIV/AIDS—PULMONARY MANIFESTATIONS (TABLE 1.4) Table 1.4 CD4 count narrows the differential for potential causes of pulmonary infection in the context of HIV and AIDS 200 cells/µL opportunistic infection and malignancy 10 cm E: Denotes extra-nodal extension or single extra-nodal site of disease Hodgkin and non-Hodgkin lymphomas are staged using the same system. HODGKIN LYMPHOMA Most present with enlarged supraclavicular/cervical lymph nodes, often with no symptoms. Diagnosis confirmed by presence of Reed–Sternberg cells. More common in the chest than non-Hodgkin. Plain film (Figure 1.25) Masses, consolidation and nodules Pleural effusions are common 68 Figure 1.25 Lymphoma. Chest x-ray demonstrating mediastinal lymphadenopathy with widening of the paratracheal stripe (white arrow) and loss of the aortopulmonary window (red arrow). CT Parenchymal disease accompanied by intrathoracic adenopathy Expect enlarged mediastinal lymph nodes (paratracheal and anterior mediastinum), hila nodes atypical Non-Hodgkin lymphoma Tends to present with slowly growing lymph nodes and B symptoms (i.e. fever, night sweats, weight loss). Far more common than Hodgkin lymphoma. About three-quarters in the thorax are diffuse large B-cell lymphoma (DLBCL). Plain film Classic appearance is hilar or mediastinal lymph node enlargement with a pleural effusion. CT Pattern of lymph node enlargement varies with lymphoma subtype (e.g. in DLBCL, prevascular/pretracheal nodes are most commonly 69  affected). May present with miliary nodules. HYDATID INFECTION The lungs are the second most common site (about 15%) after the liver to be affected. Up to 15%–25% show no symptoms. Diagnosis made with Casoni skin test or serological antigens. Expect blood eosinophilia. PLAIN FILM Multiple well-defined, rounded masses (up to 20 cm). More common in the lower lobes, may have an air–fluid level (due to communication with the bronchial tree). CT Cyst with low-density contents, rarely calcification. ‘Water lily’ sign describes the floating cyst membrane within cyst fluid. ‘Empty cyst’ sign occurs where cyst contents have been expectorated. HYPERSENSITIVITY PNEUMONITIS Also known as extrinsic allergic alveolitis, it is a granulomatous response to an inhaled antigen. The antigens involved include animal proteins (e.g. bird fancier’s lung), microbes (e.g. farmer’s lung, hot tub lung, etc.), chemicals, etc. Presentation may be acute (e.g. 6–8 hours after exposure) or chronic after years of exposure. PLAIN FILM A normal chest radiograph is the most common finding. Look for multiple poorly defined small opacities, patchy/diffuse airspace shadowing. Pleural effusions are unusual. In chronic cases, there may be fibrosis, typically in the upper zones. HRCT Patchy ground-glass change and small ill-defined centrilobular nodules. 70  Look for air-trapping giving a mosaic pattern of attenuation (i.e. trapped air in secondary lobules). IDIOPATHIC INTERSTITIAL PNEUMONIA Box 1.15 MAKE SENSE OF IDIOPATHIC INTERSTITIAL PNEUMONIA Mueller-Mang, C. et al. 2007. What every radiologist should know about idiopathic interstitial pneumonias. Radiographics 27:595–615. Hansell, D. et al. 2008. Fleischner society: Glossary of terms for thoracic imaging. Radiology 246:697–722. This is a group of seven diffuse lung diseases. They are rare, and each has its own pattern on HRCT that correlates with histological findings. Patients typically present with non-specific cough or dyspnoea. In approximate order of frequency: USUAL INTERSTITIAL PNEUMONIA (UIP) The UIP pattern is seen with idiopathic pulmonary fibrosis (IPF; the clinical syndrome). It typically affects those >50 years of age, often with a smoking history. The UIP pattern is also seen with rheumatoid lung, systemic sclerosis (can have UIP or non-specific interstitial pneumonia [NSIP] pattern), asbestosis and other connective tissue diseases. Response to steroids and prognosis is poor in IPF. Plain film Normal at first, then decreased lung volumes with sub-pleural, basal reticulation. HRCT The classic trio is: (1) apicobasal gradient of (2) sub-pleural reticular opacities, and (3) macrocystic honeycombing and traction bronchiectasis. Ground-glass attenuation less extensive than the reticular opacities. Check for an irregular pleural surface. Typically, abnormal lung is seen next to normal lung. The pattern is typical, biopsy may not be required for diagnosis. 71  10% of IPF patients develop lung cancer. NON-SPECIFIC INTERSTITIAL PNEUMONIA (NSIP) Primarily idiopathic, but the pattern may also be associated with connective tissue disorders (e.g. systemic lupus erythematosus [SLE] and systemic sclerosis), other autoimmune diseases (rheumatoid arthritis) and may be drug induced (e.g. gold). Affects younger patients than IPF and responds well to steroid treatment. Plain film Normal at first, then diffuse airspace opacities. HRCT Bilateral, symmetrical, sub-pleural ground-glass change with reticular opacities. Traction bronchiectasis and consolidation later in the disease. Ground-glass opacification dominates—not reticulation as with UIP. There may be honeycombing late in the disease (microcystic). CRYPTOGENIC ORGANISING PNEUMONIA (COP) Previously known as bronchiolitis obliterans organising pneumonia. It is characterised by the onset of cough, dyspnoea and low-grade pyrexia over several weeks. Wide age range affected, more common between 40 and 70 years of age. Plain film Bilateral, peripheral patchy consolidation. Fleeting/migratory consolidation is classic. HRCT Typically multifocal, transient, patchy, dense consolidation with a predominantly sub-pleural, mid-lower zone distribution (80%). Small centrilobular nodules and peribronchial thickening. The ‘atoll’ sign is characteristic (not pathognomic), lesion with central ground glass and rim of consolidation. Adenopathy (25%) and effusions (30%) are less common. 72  Dense consolidation helps to distinguish COP from desquamative interstitial pneumonia (DIP)—ground-glass opacification dominates in DIP RESPIRATORY BRONCHIOLITIS-ASSOCIATED INTERSTITIAL LUNG DISEASE (RB-ILD) This is the interstitial lung disease of smokers, more common in men aged 30–40 years. Treatment is with steroids and smoking cessation. HRCT Centriolobular nodules with ground glass, bronchial wall thickening and air-trapping. Expect background centrilobular emphysema (due to smoking history). DESQUAMATIVE INTERSTITIAL PNEUMONIA (DIP) Strongly associated with smoking (90% are smokers), considered the end of the RB-ILD spectrum. More common in men, the prognosis is good with steroids and smoking cessation. Plain film Non-specific, hazy opacities HRCT Diffuse ground-glass opacification not respecting fissures—this is classic. Deep parenchymal cysts. More commonly a peripheral pattern. ACUTE INTERSTITIAL PNEUMONIA (AIP) Unlike the other idiopathic interstitial pneumonias (IIPs), symptom onset is acute and rapidly progressive to requiring ventilation in 3 weeks. Steroids are effective early on, but mortality remains 50%. Plain film Diffuse patchy airspace disease (similar to ARDS), but sparing the costophrenic angles. 73 HRCT Ground-glass opacities and dependent consolidation (from oedema and haemorrhage). For survivors of the acute disease, there may be non-dependent honeycombing and traction bronchiectasis (consolidation is thought to be protective against this). LYMPHOCYTIC INTERSTITIAL PNEUMONITIS (LIP) Very rare when idiopathic. The pattern is more commonly seen in patients with Sjögren syndrome or who are immunocompromised (e.g. HIV) and have chronic, active hepatitis. More common in women. Plain film Non-specific, reticular or reticulo-nodular opacities HRCT The classic duo is: (1) diffuse ground-glass opacification; and (2) thin- walled perivascular cysts. Centrilobular nodules, septal thickening and pleural effusions are less common. KARTAGENER SYNDROME This is a type of primary ciliary dyskinesia with autosomal recessive inheritance. It comprises a triad of dextrocardia, bronchiectasis and sinusitis. The problem is due to ciliary dysfunction; in the lungs, this leads to bronchitis, recurrent pneumonia, etc. It usually presents in childhood and is associated with infertility, corneal abnormalities, transposition of the great vessels, pyloric stenosis, post-cricoid web and epispadias. PLAIN FILM Classic findings are bronchiectasis and dextrocardia. Check also for bronchial wall thickening, collapse and consolidation. LUNG CANCER 74 Lung cancer is the most common cause of cancer death worldwide. Mostly diagnosed when the disease is advanced, a minority (about 10%) are picked up incidentally. Lung cancer is divided broadly into two groups: non-small- cell lung cancer (NSCLC; 85%) and small-cell lung cancer (SCLC) (Table 1.5). Table 1.5 Basic staging of non-small-cell lung cancer Management T Characteristics Lobectomy 1 Up to 3 cm in size, no bronchial invasion 2 3–7 cm, >2 cm from carina, lobar atelectasis Pneumonectomy 3 >7 cm, 15 mm thick is worrying. 75  Nodules enhancing >15 HU are 98% sensitive, 73% specific for malignancy. Common sites for metastases include adrenal glands, liver, brain, bones and soft tissues. Nuclear medicine PET is superior for staging (92% accuracy, 25% for CT) and assessing bone disease (92% vs. 87%). False positives may arise due to inflammatory processes. SCLC This used to be known as oat-cell carcinoma. It is very aggressive and rapidly fatal without treatment (chemotherapy/radiotherapy). It is a disease of smokers and typically presents once systemic. Plain film Large central mass involving at least one hilum Lung/lobar collapse, pleural effusion CT Large central/hilar mass with associated lymph node enlargement. Encasement of the heart and great vessels—note that a quarter of all superior vena cava obstruction is due to SCLC. Nuclear medicine Bone scan is useful for detecting bone metastases. PET is used for staging. LUNG TRANSPLANT PULMONARY COMPLICATIONS Box 1.16 COMPLICATIONS OF LUNG TRANSPLANTATION Acute complications Reperfusion syndrome Acute transplant rejection Anastomotic dehiscence Any time Infection 76 Chronic Bronchiolitis obliterans PTLD REPERFUSION SYNDROME This is the most common immediate complication and occurs within 48 hours of transplant. Plain film Perihilar airspace opacification Bibasal pleural effusions ACUTE TRANSPLANT REJECTION Occurs at approximately 10 days post-transplant. Plain film Normal in 50% Otherwise heterogeneous peri-hilar opacification, septal thickening and right pleural effusion Absence of upper lobe blood diversion BRONCHIOLITIS OBLITERANS This is a leading cause of death after approximately 2 years; onset is chronic from about 3 months post-transplant. Cytomegalovirus (CMV) is a predisposing factor. Plain film/CT Normal chest x-ray initially, then decreased vascular markings and increasing bronchiectasis Hyperinflated lungs with bronchial thickening and dilatation Air trapping, mosaic perfusion and bronchiectasis POST-TRANSPLANT LYMPHOPROLIFERATIVE DISEASE (PTLD) Non-specific complication within 2 years of a bone marrow or solid organ transplant. It is due to B- or T-cell proliferation, usually following EBV infection. Responds rapidly to a reduction in immunosuppression or, alternatively, rituximab. Plain film 77  Single or multiple well-defined, slow-growing nodules Consolidation less commonly Often hilar or mediastinal lymph node enlargement INFECTION Most commonly bacterial, also CMV (nodules, consolidation and ground- glass opacification at 3–4 months post-transplant) and aspergillosis. LYMPHANGIOLEIOMYOMATOSIS (LAM) This is a rare interstitial lung disease that is more common in non-smoking women of child-bearing age. Symptoms worsen in pregnancy or with smoking. May present with spontaneous pneumothorax. Associated with tuberous sclerosis (up to 40% of tuberous scleroses). PLAIN FILM Normal initially, then hyper-expansion and small cysts. Check for a pneumothorax. HRCT Uniform, thin-walled cysts with normal intervening lung. Chylous pleural effusions. Pneumothorax. Nodules are unusual. HRCT commonly abnormal in affected children with tuberous sclerosis. LYMPHANGITIS CARCINOMATOSIS Box 1.17 CAUSES OF DIFFUSE RETICULATION Sarcoidosis Connective tissue disease, cardiac and cancer Cystic lung disease (lymphangioleiomyomatosis and Langerhans cell histiocytosis [LCH]) Occupational Idiopathic pulmonary fibrosis Drug induced 78 Lymphangitis carcinomatosis is the permeation of the lymphatics by neoplastic cells. This may occur due to tumour emboli or by direct extension from the hila or bronchogenic carcinoma. PLAIN FILM Classically, there is coarse/nodular reticulation. CT Nodular interlobular septal thickening and thickening of the bronchovascular lymphoid tissue. Unilateral lymphangitis is most commonly associated with a lung primary, bilateral usually suggests extra-thoracic malignancy (breast most commonly). MACLEOD SYNDROME Box 1.18 CAUSES OF A UNILATERAL HYPERLUCENT HEMITHORAX Work from chest wall inwards to remember them: Rotation Chest wall Poland syndrome Mastectomy Pleura Pneumothorax Lung Endobronchial obstruction (tumour, foreign body) MacLeod syndrome Bullae Congenital lobar emphysema Pneumonectomy Contralateral pleural effusion Vascular Large pulmonary embolus Also known as Swyer–James syndrome. It is often an incidental finding in an adult and follows previous childhood infectious bronchiolitis. PLAIN FILM (FIGURE 1.26) Hyperlucent lung with a paucity of vascular markings. 79  Normal or small-volume lung and hilum on the affected side. Figure 1.26 MacLeod syndrome. Chest x-ray demonstrating hyperlucency of the right hemithorax with paucity of the vascular markings. HRCT Hyperlucent lung with a paucity of vessels. Bronchiectasis and bronchial wall thickening are common. NUCLEAR MEDICINE Expect a matched ventilation/perfusion defect (non-specific). MESOTHELIOMA Mesothelioma accounts for about 1% of thoracic neoplasms, but it is the most common pleural malignancy. Mostly it is nodular (70%), with the rest being diffuse, and it originates in the parietal pleura. There is a strong association with previous asbestos exposure, with a latency period of up to 40 years. 80 PLAIN FILM Unilateral pleural effusion, pleural thickening and volume loss Calcified pleural plaques CT Nodular pleural thickening with encasement and mediastinal involvement. Check for extension below the diaphragm, which denotes T4 disease (rare). MOUNIER–KUHN SYNDROME This is congenital tracheobronchomegaly. It leads to reduced clearance of secretions and recurrent infection. CT Tracheal diameter >3 cm, the outline has a corrugated appearance. Look for bronchial or tracheal diverticulosis and distal bronchiectasis. NEUROFIBROMATOSIS The chest may be involved in neurofibromatosis type 1 (Von Recklinghausen disease), either from neurofibromata, meningocele or parenchymal lung disease. PLAIN FILM (FIGURE 1.27) Large posterior mediastinal mass (meningocele or neurofibroma). Ribbon ribs/posterior scalloping of the vertebral bodies (due to adjacent neurofibroma). Look for lung nodules—these may actually be cutaneous neurofibromata. Fibrosis at the lung bases. 81 Figure 1.27 Neurofibromatosis. Chest x-ray demonstrating a large posterior mediastinal mass with splaying and thinning of the ribs. HRCT/CT Progressive, symmetrical basal fibrosis and upper lobe bullae. Look for paravertebral masses extending into the spinal canal—soft tissue/some fat density suggests neurofibroma, fluid density suggests a lateral meningocele. PECTUS EXCAVATUM Congenital deformity of the sternum/anterior chest wall associated with Marfan syndrome, neurofibromatosis type 1 (NF1) and Ehlers–Danlos syndrome. Surgical options include insertion of a rod to displace the sternum anteriorly—the Nuss procedure. PLAIN FILM 82  Blurring of the right heart border and displacement of the heart to the left. Mimics middle lobe consolidation. Posterior ribs appear more horizontal than expected and the anterior ribs more vertical. PNEUMOCONIOSIS This is a collection of lung diseases resulting from a local reaction to inhaled particulates. It is broadly classified as fibrotic (coal worker’s pneumoconiosis [CWP], silicosis, asbestosis, berylliosis and talcosis) and non-fibrotic (tin oxide: stannosis; iron oxide: siderosis). Requires a long period of exposure. FIBROTIC CWP Due to exposure to coal dust. Increased risk of chronic obstructive pulmonary disease (COPD) and progressive massive fibrosis (PMF). Caplan syndrome is CWP with features of rheumatoid arthritis. Plain film Small, well-defined nodules of 1–5 mm with an upper lobe predominance Calcification on chest x-ray in up to 20% CT Diffuse nodules Hilar or mediastinal lymph node enlargement with or without central node calcification (eggshell calcification also sometimes present) Silicosis Due to exposure to silica (e.g. sandblasting or mining). Acute exposure to large volumes of silica causes acute silicosis (‘silicoproteinosis’)—classic silicosis is a chronic form. Becomes complicated (i.e. PMF) more commonly than CWP. Plain film (Figure 1.28) 83  Small (2 months in some cases) after successful treatment. Immunosuppression and the coexistence of diabetes, neutropenia, etc., 85 delay infiltrate formation. Cavitation suggests infection with Staphylococcus. PNEUMOCOCCAL PNEUMONIA Due to Streptococcus, it accounts for >50% of bacterial pneumonia. Plain film Consolidation with or without air bronchograms, it may be multi-lobar or bilateral. Pleural effusions are common. In children, consolidation may be mass-like, ‘round pneumonia’— more common in the lower zones. CT Consolidation appears more extensive than on plain radiography. Lymph node enlargement is common. Look for small nodules or ‘tree in bud’ opacities (small airway inflammation). Pleural effusions are common; pleural enhancement suggests empyema. VARICELLA-ZOSTER PNEUMONIA The appearance depends on the stage of the disease. Plain film/CT Multiple small nodules, some of which coalesce to form areas of consolidation when acute Miliary (i.e. small calcified) nodules in the chronic phase LIPOID PNEUMONIA Due to inadvertent inhalation of mineral oil. Plain film Chronic lower lobe consolidation, may be focal/mass-like or multi-focal CT Fat density attenuation/consolidation PNEUMOMEDIASTINUM 86  Box 1.20 THE CRITICAL REVIEW AREAS FOR CHEST X-RAYS —THE THREE PS Pneumothorax Pneumomediastinum Pneumoperitoneum Mostly due to alveolar rupture from increased intra-alveolar pressure (e.g. asthma, aspiration of foreign body, mechanical ventilation or trauma). Other causes include disease affecting the alveolar wall directly (e.g. pneumonia, ARDS or COPD), tracheal perforation and oesophageal rupture. PLAIN FILM Look for air giving the heart/mediastinum a more crisp outline than normal. Gas in the soft tissues of the neck. Large volumes dissect inferiorly into the retroperitoneum/peritoneum. PNEUMOTHORAX Appearances on a supine radiograph can be challenging and may underestimate the extent of pneumothorax. Air collects in one or more of the pleural recesses—most common locations are subpulmonic and anteromedial. PLAIN FILM (SUPINE CHEST X-RAY) Hyperlucent right upper quadrant ‘Deep sulcus’ sign, an excessively sharp contour to the hemidiaphragm POLAND SYNDROME Congenital, unilateral absence of part or whole of the pectoralis major. Associated with deformity of the fingers, ribs and pectus excavatum. PLAIN FILM Apparent hyperlucent lung (underlying lung is actually normal) due to the absence of overlying soft tissue Pulmonary alveolar microlithiasis Asymptomatic in 70% of patients (despite florid appearances on imaging!). Typically presents at age 30–50 years, more common in Turkey. 87 PLAIN FILM Diffuse, dense miliary calcification, which may obscure borders with the mediastinum, diaphragm, etc. Sub-pleural cyst formation may give the pleura a lucent appearance on chest x-ray. CT Numerous bilateral calcifications, may be most conspicuous in the mid- lower zones and along the microvascular bundles. PULMONARY ALVEOLAR PROTEINOSIS Typically affecting middle-aged men, they present with a dry cough and clubbing. There is a strong association with smoking. It is mostly primary (90%). The rest arises due to acute silicosis, haematological malignancy or in the context of infection with immunosuppression (e.g. Cryptococcus, Nocardia or Aspergillus). Characterised by the filling of airspaces with proteinaceous fluid—the interstitium is not affected. PLAIN FILM Symmetrical peri-hilar ground-glass opacification, mimics pulmonary oedema No pleural effusion or cardiomegaly HRCT A crazy-paving appearance is classic (less common in secondary disease)—a combination of ground-glass opacification and smooth interlobular septal thickening. Ground-glass opacification predominates (the ‘black bronchus’ sign is useful for demonstrating ground-glass opacification). PULMONARY EMBOLISM Patients are typically risk stratified first with the modified Wells score, with those at high risk proceeding to CT pulmonary angiography and low-risk patients having a D-dimer test. CTPA sensitivity is 83% (increased slightly by doing a CT venogram at the same time) and specificity is 96%. US 88  Used to assess the deep veins of the legs, as most pulmonary embolisms (PEs) originate here. Expanded, non-compressible vessel. Reduced venous flow on calf compression. CT Occlusive/non-occlusive filling defect that forms an acute angle with the vessel wall. Look for peripheral wedge-shaped foci of consolidation (pulmonary infarct) and, more rarely, mosaic attenuation of the lung (pulmonary oligaemia). Chronic PE—forms an obtuse angle with the vessel wall, crescentic arrangement within the vessel. There may be webs, calcification or collateralisation. Mosaic attenuation (Figure 1.29) is seen more commonly than with acute PE. Check for evidence of acute right heart strain (e.g. enlarged right ventricle, reflux of contrast to the hepatic veins, bowing of the intraventricular septum towards the left ventricle and pulmonary hypertension). 89 Figure 1.29 Chronic thromboembolism. High-resolution computed tomography image demonstrating mosaic attenuation. The hypoattenuating regions are abnormal and reflect oligaemia. The vessels within the hypoattenuating regions are small (white arrow). NUCLEAR MEDICINE Sensitivity is similar to a CTPA test, but less specific. V/Q is now usually performed either in pregnancy (depending on local guidelines) or when renal failure precludes the use of intravenous contrast. INTERVENTION Catheter-directed thrombolysis/mechanical thrombectomy may be considered for certain patients with life-threatening PE. PULMONARY HYPERTENSION Divided into primary and secondary causes. Secondary pulmonary hypertension is due to either increased pulmonary blood flow (e.g. left to right shunt), decreased cross-sectional area of the pulmonary vasculature (e.g. pulmonary embolism) or increased resistance to pulmonary venous drainage (commonly due to left-sided heart disease). PLAIN FILM Look for an enlarged right descending pulmonary artery (>25 mm). Peripheral oligaemia. CT Main pulmonary artery wider than the ascending aorta (or >28–30 mm) Mosaic attenuation of the lungs due to variations in perfusion PULMONARY LANGERHANS CELL HISTIOCYTOSIS Rare disease that is most common in smokers aged 30–40 years, thought to be due to antigen exposure (hence it predominates in the upper zones of the lungs). HRCT 90  Early on, nodules are most common in the mid-upper zones. As the disease progresses, the nodules undergo cystic degeneration. Eventually, the cysts may coalesce to form a honeycomb pattern (Figure 1.30). The presence of 3–10-mm nodules and cysts in the upper zones in a smoker is strongly suggestive of histiocytosis. Figure 1.30 Langerhans cell histiocytosis. HRCT image demonstrating bilateral lung cysts with coalescence into a honeycomb pattern (white arrow). PULMONARY OEDEMA The accumulation of extravascular fluid in the lung. It is either due to increased fluid pressure (leading first to increased interstitial fluid, then to alveolar flooding) or to increased membrane permeability. PLAIN FILM Initially, there is vascular redistribution—‘upper lobe diversion’. 91  Then, interstitial fluid and Kerley lines (Kerley A lines are 2–6 cm long, extend from the hila; Kerley B lines are 7 mm) or the biceps tendon (>4 mm) or cuff tears Joint/bursa effusion MRI Bone lesions are low signal on T1 (variable T2 signal) and enhance following gadolinium. Thickened synovium of low signal on T2. Intrarticular nodules, which are low signal on T1 and T2, communicate with the subchondral bone lesions. ANKYLOSING SPONDYLITIS Box 2.2 COMMON CAUSES OF SACROILIITIS Tends to affect the lower joint (i.e. the synovial portion) Symmetrical Anklyosing spondylitis 105  Inflammatory bowel disease Rheumatoid arthritis Asymmetrical Osteoarthritis Psoriasis/reactive arthritis Septic arthritis This is the most common seronegative (i.e. rheumatoid factor-negative) spondyloarthropathy leading to progressive joint fusion. It is more common in males and has a predilection for the sacroiliac joints and spine. It is commonly associated with the HLA-B27 gene. SACROILIAC JOINT X-RAY First joint affected, typically bilateral and symmetrical Periarticular osteoporosis and joint widening initially Sclerosis as the disease progresses Complete joint fusion in late disease (Figure 2.1) 106 Figure 2.1 Ankylosing spondylitis. Pelvic x-ray demonstrating fusion of the sacroiliac (white arrows) joint. SPINE X-RAY Sclerosis at the edge of the discovertebral joints (‘shiny corner’) and erosion (‘Romanus lesions’) are early signs. Squared vertebral bodies (more obvious in the lumbar spine). Progressive growth of syndesmophytes (ossification of the outer fibres of the annulus fibrosus)—these eventually bridge the disc and cause ankylosis. As more bone forms, the spine develops a smooth, undulating contour ‘bamboo spine’. Prominent thoracic kyphosis and limited lumbar lordosis. Erosion of the endplate. Facet joint ankyloses. Look for three-column fractures—the ankylosed spine is very susceptible to fracture. Signs: ‘dagger’ sign (ossification of the supraspinous and interspinous ligaments on frontal radiographs) and ‘trolley track’ (denotes three vertically orientated dense lines corresponding to ossified supraspinous and interspinous ligaments; Figure 2.2). 107 Figure 2.2 Ankylosing spondylitis. Frontal lumbar spine radiograph demonstrating the dagger sign (flowing ossification of the supraspinous and interspinous ligaments in a single dense line [white arrows]) and the trolley track sign (ossification of the apophyseal joints [red arrows] as well as the supraspinous and interspinous ligaments). MRI Useful to aid early diagnosis and monitor disease activity. Periarticular high signal at the sacroiliac joints on STIR (i.e. oedema), marrow/sacroiliac (SI) joint enhancement with gadolinium. The hyperaemia and oedema at the anterior corners of the vertebral body cause high T2 signal—Romanus lesions (Figure 2.3). Look for fractures (low signal on T1, high signal on T2/STIR); these commonly occur horizontally through the intervertebral disc and may cause disc herniation and cord compression. 108 Figure 2.3 Ankylosing spondylitis. Sagittal T2-weighted magnetic resonance image demonstrating high T2 signal/oedema at the anterior corners of the vertebral body— Romanus lesions (white arrows). Box 2.3 SYNDESMOPHYTES VERSUS OSTEOPHYTES 1. Syndesmophytes have a vertical orientation 2. Osteophytes arise a few millimetres from the discovertebral junction 3. Osteophytes are triangular in shape 109  4. New bone formation in diffuse idiopathic skeletal hyperplasia arises from the anterior longitudinal ligament and is prolific AVASCULAR NECROSIS (AVN) Box 2.4 EPONYMOUS NAMES FOR AVASCULAR NECROSIS Hip (Perthe disease) Medial tibial condyle (Blount disease) Metatarsal head (Freiberg infarction) Lunate (Kienbock malacia) Navicular (Köhler disease; Figure 2.4) Capitellum (Panner disease) Scaphoid (Preiser disease) Vertebral body (Kummel disease) Figure 2.4 Köhler disease. Foot x-ray demonstrating sclerosis and flattening of the navicular in keeping with avascular necrosis (Köhler disease). 110 Interruption of blood supply causes the cell death of the bone constituents, mostly due to an arterial problem (it can also be due to venous insufficiency). It can affect any bone, but the hip is most commonly affected. It affects the epiphysis (if it affects the diaphysis or metaphysis, it is known as bone infarction). Causes include trauma, haematological conditions (systemic lupus erythematosus [SLE], Gaucher disease or sickle cell anaemia), Cushing syndrome, steroid use, alcoholism, pancreatitis, pregnancy, Caisson disease, etc. Patients taking steroids and transplant recipients are especially at risk. PLAIN FILM (FIGURE 2.5) Focal radiolucencies Sclerosis Bone collapse Loss of joint space Figure 2.5 Avascular necrosis. Pelvic x-ray demonstrating bony sclerosis with irregularity and flattening of the left femoral head. Note the pelvic clips, anastomosis and femoral line in keeping with renal failure/transplant with steroids, therefore being the likely cause of the avascular necrosis. MRI Most sensitive for diagnosis. Low signal on T1 and intermediate signal on T2 (reflects adipocyte death). 111  Surrounding high signal on T2/STIR indicates oedema (suggesting an acute event). Oedema localises to the subchondral surface with increased severity, with an irregular rim of low T1 signal. ‘Double line’ sign (paired rims of low and high signal on T2 demonstrating the interface of viable/dying bone marrow). BONE SCAN 80%–85% sensitive. Early disease is demonstrated by a focus of reduced tracer uptake. In late disease, there is a focus of reduced uptake surrounded by a ring of increased uptake (‘doughnut sign’) due to capillary revascularisation and bone synthesis. BASILAR INVAGINATION Occurs where the tip of the dens protrudes above the basion–opisthion line (the opening of the foramen magnum, also known as the McRae line). Commonly associated with rheumatoid arthritis (RA; 10% affected) and platybasia (flattening of the skull base, cranial basal angle >136°), as well as rickets, osteomalacia, osteogenesis imperfecta, Paget disease, fibrous dysplasia, Klippel–Feil syndrome and hyperparathyroidism. CT Sagittal reformat shows tip of the dens 15 mm2 MRI The most specific sign is an abrupt change in the diameter of the median nerve. Increased signal intensity of the median nerve on T2. Median nerve enhances with gadolinium. 115  Compression and flattening of the median nerve. Volar bowing of the flexor retinaculum. Pseudoneuroma of the median nerve. CHARCOT ARTHROPATHY (NEUROPATHIC JOINT) Box 2.5 THE D’S OF A NEUROPATHIC (CHARCOT) JOINT Destruction of the articular cartilage Degeneration (joint space loss) Debris (loose bodies) Dislocation Distension of the joint (i.e. effusion) Density of bone normal for the patient This is a destructive joint process arising from nerve damage, most commonly secondary to diabetes. The involvement of particular joints may indicate the underlying aetiology. Ankle/foot—diabetes Shoulder—syringomyelia Spine—spinal cord injury Knee—diabetes/syphilis PLAIN FILM The D’s (see Box 2.5). The presence of loose bodies and subchondral cysts favours a neuropathic joint over septic arthritis. MRI Subchondral enhancement following gadolinium Non-specific bone marrow oedema CHONDROMALACIA PATELLA This typically occurs in adolescents and young adults. It is a common cause of anterior knee pain associated with trauma, chronic stress and patella instability. There is softening and oedema of the articular cartilage (grade I); 116 this may progress to fissure/fragmentation 1.3 cm (grade III) and full-thickness cartilage loss (grade IV). May heal or progress to osteoarthritis. PLAIN FILM Insensitive, shows non-specific loss of joint space. MRI Axial T2-weighted/intermediate-weighted imaging with fat suppression. Thinning of the cartilage in the patella–femoral joint. Joint fluid extends to the bone with full-thickness cartilage defects. Look for bone oedema and subchondral cystic change. CYSTICERCOSIS Due to Taenia solium, a tapeworm found in pork. It can affect any organ, most commonly the brain, eye and muscle. PLAIN FILM Characteristic multiple rice-like calcifications aligned in the direction of the muscle fibres Dermatomyositis This is an idiopathic inflammatory myopathy with deposition of complement or inflammatory infiltrate in the skeletal muscle and subcutaneous tissue. It affects children and adults. It is associated with malignant neoplasms in up to 25%, particularly genitourinary, gynaecological, oesophageal, lung and melanoma. There is also an increased risk of venous thromboembolism and myocardial infarction. PLAIN FILM (FIGURE 2.6) Non-specific subcutaneous calcification. Sheet-like calcifications along fascial or muscle planes of the proximal large muscles are less common; however, these are pathognomonic. 117 Figure 2.6 Dermatomyositis. Pelvic x-ray demonstrating sheet-like calcification along muscular/fascial planes, particularly above the left hip (white arrow). HIGH-RESOLUTION CT (HRCT) 67% have interstitial lung disease. Most commonly there is subpleural consolidation (bronchiolitis obliterans organising pneumonia [BOOP]). BOOP may progress to subpleural honeycombing and usual interstitial pneumonia. Bronchiolitis (‘tree in bud’), ill-defined airspace opacification suggests chronic aspiration pneumonia. MRI Muscle oedema early, followed by calcification and atrophy. High T2 signal intensity seen in the muscles suggests oedema, enhancement seen on T1 post-contrast. Fatty infiltration late in the disease (high signal on T1 and T2). DIFFUSE IDIOPATHIC SKELETAL HYPERPLASIA This is an ankylosing disorder of the spine. Symptoms are mild, consisting of restricted motion and tendinitis from enthesopathy. X-RAY SPINE/CT 118  Undulating soft tissue calcification and hyperostosis along the anterolateral aspect of the spine (‘dripping candle wax’). For diagnosis: affects four or more adjacent vertebrae; intervertebral disc height is preserved; the sacroiliac joints and apophyseal joints (spine) are spared. OTHER X-RAYS ‘Whiskering’ of the iliac crest (fluffy calcification representing enthesopathy); may also affect the calcaneum (spurs) and olecranon. Ossification of the iliolumbar, sacroiliac and sacrotuberous ligaments and patella tendon. Soft tissue calcification adjacent to the lateral epicondyle (tennis elbow). DISCECTOMY (SCAR VS. RECURRENT DISC) In patients with continued back pain post-discectomy/laminectomy, the cause may be either post-operative epidural fibrosis (i.e. scar tissue) or recurrent disc herniation. MRI Pre- and post-contrast T1 imaging Scar: epi