Radiography of the Abdomen Lecture PDF

Abdomen X-rays - Edward Newcome ([email protected]) Page 2  Pre-reading Week 10: Abdomen Frank, E.D., Long, B.W., & Smith, B.J. (2016) Merrill’s Atlas of Radiographic Positioning and Procedures (13th ed. Vol. 2 St Louis: Mosby (pg. 130-135) OR Bontrager, K. L., & Lampignano, J. P....

Abdomen X-rays - Edward Newcome ([email protected]) Page 2  Pre-reading Week 10: Abdomen Frank, E.D., Long, B.W., & Smith, B.J. (2016) Merrill’s Atlas of Radiographic Positioning and Procedures (13th ed. Vol. 2 St Louis: Mosby (pg. 130-135) OR Bontrager, K. L., & Lampignano, J. P. (2013) Textbook of Radiographic Positioning and Related Anatomy (8th ed.). St Louis: Elsevier Mosby (pg.103-123) AND McQuillen-Martensen, K. (2020) Radiographic Image Analysis, 5th edn. W.B. Saunders Company, Sydney (pg.138-159) Page 3  Learning Objectives Having undertaken the prescribed reading, attending this lecture and participated in labs and self-directed learning activities you should be able to: Describe the anatomy of the abdomen and identify organ position Describe and justify the technical factors for radiography of the abdomen Explain and justify exposures for an acute abdomen Describe, adapt and justify patient positioning in radiography of the abdomen Evaluate radiographs of the abdomen Demonstrate knowledge of pathology using appropriate terminology and outline pathology related technique modifications Page 4 Abdominal Anatomy Page 5  Anatomy Diagram courtesy of < https://www.medicalnewstoday.com/articles/stomach-diagram#diagram > Page 6 Anatomy Page 7  Digestive System Diagram courtesy of < https://www.cancer.gov/publications/dictionaries/cancer-terms/def/small-intestine > Page 8  Digestive System Image courtesy of Brent Burbridge < https://mistr.usask.ca/odin/?caseID=20170825121322404 > Page 9  Urinary System Diagram courtesy of < https://www.niddk.nih.gov/health-information/urologic-diseases/urinary-tract-how-it-works > Page 10 Abdominal X-Ray Anatomy Diagram courtesy of by Dr Sachintha Hapugoda < https://radiopaedia.org/cases/56646 > Page 11 Abdominal X-Ray Anatomy Diagram courtesy of Page 12  Normal AXR Diagram courtesy of < https://www.radiologymasterclass.co.uk/gallery/abdo/abdominal_xray/normal > Page 13 Common Indications Page 14  Clinical Indications for Abdominal X-rays - Free Fluid (blood) - Foreign Bodies - Pathology - Obstruction - Metastatic Disease - Renal Calculi - Inflammatory Disease (ascites) - Hernia - Trauma (penetrating trauma/free air) - Stabbing - Gunshot - Impaling Page 15  Common Indications Look for these things: Gases Masses Bones Stones Fluid and Foreign Bodies Page 16  Gases Free gas (Extraluminal gas) Dilated small and large bowels (Intraluminal gas) Page 17  Pneumoperitoneum – Free gas Pneumoperitoneum (free gas), is gas or air trapped within the peritoneal cavity, but outside the lumen of the bowel. Can be due to bowel perforation, or due to insufflation of gas (CO2 or air) during laparoscopy. **Both these causes have identical x-ray appearances, but very different clinical significance Page 18  Pneumoperitoneum – Free gas On an erect x-ray, the free gas will be trapped under the diaphragm. An ERECT CHEST x-ray is much more sensitive in detecting a pneumoperitoneum, but there are several signs that may be useful in detecting free gas in an abdominal x-ray Page 19  Pneumoperitoneum – Rigler’s RIGLER’S/DOUBLE WALL SIGN is the appearance of lucency (gas) on both sides of the bowel wall Normally only the inner wall of the bowel is visible Gas separates the bowel segments and forms sharp angles Page 20 Pneumoperitoneum – Football sign Football Sign: a large volume of free gas has risen to the front of the peritoneal cavity resulting in a large round black area. Rigler’s sign is also visible Page 21 Pneumoperitoneum – Football sign Football Sign: a large volume of free gas has risen to the front of the peritoneal cavity resulting in a large round black area. Rigler’s sign is also visible Page 22  Bowel Obstruction Bowel obstructions are common and account for 20% of admissions with "surgical abdomens". Radiology is important in confirming the diagnosis and identifying the underlying cause. Bowel obstructions are usually divided according to where the obstruction occurs: Large bowel obstruction Small bowel obstruction The classic clinical features of bowel obstruction are: colicky abdominal pain vomiting abdominal distension absolute constipation For large bowel obstructions, generally there is absolute constipation For small bowel obstructions generally it begins with vomiting Page 23  Large Bowel Obstruction Large bowel obstruction (LBO) are not as common as small bowel obstructions. They require prompt diagnosis and treatment. As dilatation of the colon increases, the risk of perforation is also increased. Perforation may occur at the site of obstruction, or more proximally secondary to ischaemic change. Case courtesy of Dr Varun Babu, Radiopaedia.org, rID: 18015 Page 24 Large Bowel Obstruction Dilatation of the caecum >9cm, and >6cm for the rest of the colon is considered abnormal. Presentation typically include: abdominal pain distension failure of passage of gas and stool. The most common causes are: Diverticular strictures Rectal cancer Page 25 Large Bowel Obstruction Colon is dilated to the level of the distal descending colon There is a soft tissue density evident at the level of the obstruction Obstruction is NOT absolute as there is gas in the rectum Page 26  Pseudo-obstruction Colonic Pseudo-obstruction is a functional abnormality of the bowel which has similar clinical features to true obstruction, but no mechanical cause is found. Can lead to bowel necrosis and perforation, potentially causing generalized peritonitis and death. Most often occurs in the elderly population, in those with underlying systemic medical conditions, or due to certain drugs. Case courtesy of Radiopaedia.org, rID: 11684 Page 27  Small Bowel Obstruction The most common causes of small bowel obstruction are: adhesions secondary to intra- abdominal surgery hernias Tumours Crohn's disease Dilatation >3cm of the small bowel is considered abnormal, however the longer the segment of bowel that is dilated, the more likely bowel dilatation represents a genuine obstruction. Abdominal radiographs are only Case courtesy of Brent Burbridge 50-60% sensitive for small bowel obstruction. Page 28  Small Bowel Obstruction Abdominal radiographs may have the following features: dilated loops of small bowel proximal to the obstruction predominantly central dilated loops three instances of dilatation >3cm valvulae conniventes are visible fluid levels if the study is erect the string-of-pearls sign: small pockets of gas within a fluid-filled small bowel a gasless abdomen: gas within the small bowel is a function of vomiting, NGT placement and level of obstruction Page 29  String of Pearls String of pearls (or beads) sign can be seen on erect or decubitus images and CT in patients with small bowel obstruction These appear an obliquely or horizontally oriented row of small gas bubbles in the abdomen, which represent small pockets of gas along the superior wall of the small bowel that are trapped between the valvulae conniventes. **Valvulae conniventes are the Case courtesy of Dr Maulik S Patel, Radiopaedia.org, rID: 13853 mucosal folds of the small intestine, starting from the second part of the duodenum. Page 30 Normal appearance of Small Bowel A normal small bowel meal demonstrates the rugal folds in the stomach and the valvulae conniventes of the small bowel Page 31  Small Bowel Obstruction Case courtesy of Dr Ahmed Abd Rabou, Radiopaedia.org, rID: 35721 This abdominal film demonstrates why the abdomen is distended. There are multiple loops of gas-filled small bowel which are in a predominantly central distribution. Page 32 Ileus Ileus is a term used for aperistaltic bowel not caused by a mechanical obstruction. This phenomenon is common after abdominal surgery. The radiological features can be similar to those of obstruction. ** There are multiple loops of gas filled bowel projected centrally over the abdomen Page 33  Volvulus Volvulus is twisting of the bowel and is a specific cause of obstruction with characteristic radiograph appearances The two most common types of bowel twisting are: sigmoid volvulus caecal volvulus The sigmoid colon is more prone to twisting than other segments of the large bowel because it is “mobile” on its own mesentery, which arises from a fixed point in the left iliac fossa (LIF). Page 34  Sigmoid Volvulus The Sigmoid colon is more prone to twisting than other segments of the large bowel because it is 'mobile' on its own mesentery, which arises from a fixed point in the left iliac fossa (LIF). Twisting at the root of the mesentery results in the formation of an enclosed loop of sigmoid colon which becomes very dilated. If untreated this can lead either to perforation, due to excessive dilatation, or to ischaemia due to compromise of the blood supply. The coffee bean sign is indicative of a sigmoid volvulus Page 35  Sigmoid Volvulus The Sigmoid colon is more prone to twisting than other segments of the large bowel because it is 'mobile' on its own mesentery, which arises from a fixed point in the left iliac fossa (LIF). Twisting at the root of the mesentery results in the formation of an enclosed loop of sigmoid colon which becomes very dilated. If untreated this can lead either to perforation, due to excessive dilatation, or to ischaemia due to compromise of the blood supply. The coffee bean sign is indicative of a sigmoid volvulus Page 36  Caecal Volvulus The caecum is most frequently a retroperitoneal structure, and therefore not susceptible to twisting. Sometimes, due to congenital factors there is incomplete peritoneal covering of the caecum with formation of a 'mobile' caecum on a mesentery, such that it no longer lies in the right iliac fossa. This is a normal variant but is associated with increased incidence of folding or twisting of the caecum (caecal volvulus), which may be complicated by obstruction, vascular compromise, or perforation. Page 37 Toxic Megacolon Toxic megacolon is a potentially life-threatening condition characterized by dilatation of the large bowel without obstruction, in the context of acute bowel inflammation. This may be due to inflammatory bowel disease, especially ulcerative colitis, or other causes of colitis such as infection. Page 38  Air in the Liver Pneumobilia is air in the biliary tree. Radiolucent area located centrally within the liver. Case courtesy of James B, Kelly B. The abdominal radiograph. Ulster Med J. 2013 Sep;82(3):179-87. PMID: 24505155; PMCID: PMC3913410. Page 39  Air in the Liver Portal Venous Gas is gas in the portal venous system of the liver. Radiolucent area around the periphery of the liver. Almost always represents life- threatening intra-abdominal pathology such a bowel ischaemia or necrosis. Case courtesy of James B, Kelly B. The abdominal radiograph. Ulster Med J. 2013 Sep;82(3):179-87. PMID: 24505155; PMCID: PMC3913410. Page 40  Masses CT is preferred to X-ray. Masses will appear as more solid areas, but the main way to identify a mass is displacement of organs and other structures (particularly gas-filled bowels). Case courtesy of Assoc Prof Frank Gaillard, Radiopaedia.org, rID: 5957 Page 41  Bones Abnormalities of visible bones may be incidentally found, or could be contributing to symptoms Image courtesy of 1. Left rib, 2. Spinous process, 3. Transverse process, 4. Pedicles of L3 vertebra, 5. Right psoas muscle, 6. L4 vertebral body, 7. Right iliac/ischial/pubic bones, 8. Sacrum, 9. Left femoral head. Page 42  Stones Appear as bright, radio-opaque areas on the image. Can cause pain in patients, as they obstruct tracts. Renal/ureteric/bladder stones or urolithiasis (80-90% of renal tract stones are radio-opaque) Case courtesy of Assoc Prof Frank Gaillard, Radiopaedia.org, rID: 12555 Gallstones or cholelithiasis (15% are radio-opaque, these appear in the RUQ) CT or US required to confirm position Page 43 Ureteric Calculi Ureteric calculi or stones are those lying within the ureter, at any point from the pelvico-ureteric junction to the vesico- ureteric junction. They are the classic cause of renal colic type abdominal pain. Other presentations may include: haematuria nausea and vomiting. Up to 80% of renal calculi are formed by calcium stones. Other types include struvite, uric acid and cystine stones. Calculi formation may occur where stone forming substances such as calcium or uric acid supersaturate the urine, beginning crystal formation. Page 44  Ureteric Calculi A plain abdominal (KUB) film can identify large radiopaque calculi. However, smaller calculi and/or radiolucent stones may go undetected. Obstruction/hydronephrosis cannot be adequately assessed. Case courtesy of Dr Ian Bickle, Case courtesy of Dr. Ali Abougazia, Radiopaedia.org, rID: 46620 Radiopaedia.org, rID: 22713 Page 45  Ureteric Calculi Case courtesy of Dr Ian Bickle, Case courtesy of Dr Bruno Di Muzio, Radiopaedia.org, rID: 23323 Radiopaedia.org, rID: 39506 Page 46  Fluid - Ascites Ascites is defined as an abnormal amount of intraperitoneal fluid. Patients with large volume of ascites can present with abdominal distension (which may be painful), nausea, vomiting, dyspnoea and peripheral oedema. Ascitic fluid is traditionally characterised as either: Transudate: thin, low protein count, leakage from vascular system Exudate: high protein count, tissue leakage due to inflammation or local cellular damage Causes of ascites: hepatic cirrhosis alcoholic hepatitis heart failure (CCF) portal vein thrombosis peritoneal dialysis peritoneal carcinomatosis Pancreatitis peritonitis, e.g. tuberculosis ischaemic bowel bowel obstruction Case courtesy of Dr Bruno Di Muzio, Radiopaedia.org, rID: 44167 Page 47  Ascites diffusely increased density of the abdomen poor definition of the the soft tissue shadows, such as the psoas muscles, liver and spleen medial displacement of bowel and solid viscera increased separation of small bowel loops Case courtesy of Dr Bruno Di Muzio, Radiopaedia.org, rID: 44167 Case courtesy of RMH Core Conditions, Radiopaedia.org, rID: 33611 Page 48 Foreign Bodies Page 49 Abdomen X-ray Projections Page 50  Acute Abdomen Series The acute abdominal series is a common set of abdominal radiographs obtained to evaluate bowel gas. Key features that can be evaluated on these radiographs include the amount of bowel gas, with possible bowel distention air-fluid levels pneumoperitoneum A standard acute abdominal series may include: AP supine Abdomen PA erect Abdomen PA erect Chest For a patient who can’t stand or sit upright: AP supine Abdomen Left lateral decubitus Abdomen AP supine or semi-erect chest Page 51  Acute Abdomen Series The AP supine abdomen X-ray is commonly performed first as it provides the majority of the information. The decubitus view can be used to demonstrate air-fluid levels and intraperitoneal free gas when erect images cannot be taken. For the erect views, the patient should be left to sit up for 5-10 minutes to allow small amounts of free gas to drift up to the diaphragm. For the decubitus, patients lie on their left side for 5-10 minutes to allow the gas to gather along lateral liver edge. Page 52  Common Requests Constipated ++ Vomiting, nausea, ? SBO unable to pass stools AXR AXR RUQ pain, rigid abdomen ? Obstruction AXR RIF pain, tender Absent bowel sounds on ++ ? auscultation Obstruction AXR AXR Page 53  Patient Prep Positive identification of patient (using 4 W’s) Identification of pregnancy You must remove piercings where possible, bra, pants that have zips/buttons (anything metallic), contents of pockets Generally patients are changed into a hospital gown or scrubs Page 54  AP Supine Abdomen Technical Factors: 80 kVp, ~40mAs (AEC used in bucky) As short an exposure time as possible for easier patient breath hold (~0.01s) Minimum 100cm SID Large focal spot Grid used Large detector (35x43) portrait or two images taken in landscape as required. Respiration: Expiration is ideal, to separate abdominal organs as much as possible. Many radiographers use inspiration, to try and get the entire abdomen in one image (reducing dose) Don’t forget a side-marker. Image courtesy of Brent Burbridge Page 55  AP Supine Abdomen Patient Position: Part Position: Supine on X-ray table, bed or trolley Centre IR to level of iliac crests, with Centre the mid-sagittal plane of the bottom margin at symphysis pubis. body to the midline of the grid No rotation of pelvis (both ASIS are Move the patient’s arms out of the equidistant from tabletop) or shoulders. image Central Ray: Collimation: Perpendicular to IR, and directed to Laterally to lateral abdominal wall level of iliac crest, to the centre of the Inferior to inferior pubic rami abdomen side-to-side. Superior to the diaphragm Page 56 AP Supine Abdomen Page 57  KUB X-Ray Demonstrates the Kidneys, Ureters and Bladder. Similar positioning and centring point as the AP supine abdomen Only need to include above kidneys superiorly (meaning generally only one image is required). Case courtesy of Assoc Prof Frank Gaillard, Radiopaedia.org, rID: 12555 Page 58 AP Supine Abdomen/KUB X-Ray NO rotation Sacrum in the centre of the pelvis inlet. Obturator foramen should be open to the same degree and symmetrical bilaterally. Anatomy demonstrated should be: ?diaphragm Page 59 AP Supine Abdomen/KUB X-Ray Exposure – able to visualise: Kidney shadows. Page 60  PA/AP Erect Abdomen Technical Factors: 80 kVp, ~40mAs (AEC used in bucky) As short an exposure time as possible for easier patient breath hold (~0.01s) Minimum 100cm SID Large focal spot Grid used Large detector (35x43) portrait Respiration: Expiration is ideal, to separate abdominal organs as much as possible. Don’t forget a side-marker. Annotate image as “Erect” (and “PA” if taken PA) Image courtesy of Brent Burbridge Page 61  PA/AP Erect Abdomen Patient Position: Central Ray: Erect against bucky (facing Perpendicular to IR, and towards or away) or sitting directed ~5cm above level of up in bed. iliac crests, in the centre of Centre the mid-sagittal the abdomen side-to-side. plane of the body to the midline of the grid. Collimation: Move the patient’s arms Laterally to lateral abdominal out of the image. wall Superior to include all of the Part Position: diaphragm Centre of IR should be ~5cm Inferior to include as much of above level of iliac crests, the lower abdomen as with top of IR at approx. possible level of axilla for most patients. No rotation of pelvis (both ASIS are equidistant from tabletop) or shoulders. Page 62 AP Erect Abdomen Page 63 PA Erect Abdomen Page 64  Lateral Decubitus Abdomen Technical Factors: 80 kVp, ~40mAs (AEC used in bucky) As short an exposure time as possible for easier patient breath hold (~0.01s) Minimum 100cm SID Large focal spot Grid used Large detector (35x43) portrait Respiration: Expiration is ideal, to separate abdominal organs as much as possible. Don’t forget a side-marker. Annotate image as “Decubitus” Produces an AP image Page 65  Lateral Decubitus Abdomen Patient Position: Part Position: Lying on left side on table, bed or trolley Centre of IR should be ~5cm above level As close to detector/bucky as possible of iliac crests, with top of IR at approx. Centre the mid-sagittal plane of the level of axilla for most patients. body to the midline of the grid No rotation of pelvis (both ASIS are Move the patient’s arms out of the equidistant from tabletop) or shoulders. image Central Ray: Collimation: Perpendicular to IR, and directed to Laterally to lateral abdominal wall level of iliac crest, to the centre of the Superior to include all of the diaphragm abdomen side-to-side. Inferior to include as much of the lower Adjust vertically as required to ensure abdomen as possible that upside of abdomen is included Page 66 Lateral Decubitus Abdomen Page 67  Lateral Decubitus Abdomen AP abdomen, left lateral decubitus position showing free air collection along right flank. Note the correct placement of the marker. Page 68  AXRs in clinical practice A large amount of sites are moving towards eliminating erect (and decubitus) AXRs due to their high dose and the limited information they provide. Supine AXRs provide the majority of diagnostic information in the abdomen. An erect CXR demonstrates the most pressing pathologies which an erect AXR would help diagnose (as free gas will rise to the top of the abdomen), with much less dose to the patient (and providing a view of the chest which is generally more important clinically). Page 69  AXRs in clinical practice As CT scans are now more widely available and are being performed with much lower doses, they are increasingly replacing many AXR requests. CT scans of the abdomen (especially with IV contrast) provide vastly more diagnostic information. Page 70 Thanks, and see you at the Abdomen X-Ray Image Critique Tute Page 71