24 Questions
What is a possible consequence of acute cortical necrosis?
Calcification in the cortex
What is a characteristic feature of medullary changes in acute conditions involving primarily the medulla?
Enlargement of medullary pyramids due to oedema
What is a possible cause of increased medullary reflectivity?
Nephrocalcinosis of any etiology
What is a common association of renal vein thrombosis?
Nephrotic syndrome
What is a rare presentation of renal vein thrombosis in adults?
Acute
What is a possible consequence of acute cortical necrosis on corticomedullary differentiation?
Loss of corticomedullary differentiation
What is a possible cause of decreased corticomedullary differentiation?
Acute glomerulonephritis
What is a common occurrence of renal vein thrombosis in infants?
Up to 40%
What happens to corticomedullary differentiation in the kidney after 3-4 weeks of renal vein thrombosis?
It is lost
What is the characteristic feature of the kidney in renal vein thrombosis after 1-2 months?
Abnormally high reflectivity
What can be demonstrated in the renal veins of some patients with renal vein thrombosis?
Thrombus extension into the IVC
What is the characteristic feature of the affected kidney in unilateral renal artery occlusion in the immediate acute stage?
Normal size and normal reflectivity
What can be seen in some patients with renal artery occlusion?
A subcapsular 'halo' or rim of echo poor tissue
What is the characteristic feature of the affected kidney in the longer term after renal artery occlusion?
It slowly shrinks with smooth margins
What is the role of echoenhancing agents in the diagnosis of renal artery occlusion?
To increase diagnostic certainty
What is the significance of colour or power Doppler ultrasound in the diagnosis of renal artery occlusion?
It fails to show any arterial flow within the kidney
What is the most common underlying renal pathology that produces nephrotic syndrome, leading to renal vein thrombosis?
Membranous nephropathy
Which condition is more commonly associated with renal vein thrombosis in infants?
Dehydration
What is the characteristic sonographic appearance of the kidney in sudden complete occlusion of the main renal vein?
Enlarged, echo-poor kidney
What can be distinguished within the generally echo-poor tissue in cases of renal vein thrombosis?
Echo-free areas of haemorrhagic infarcts
What is a rare presentation of left renal vein occlusion in males?
Acute left varicocele
What is a common complication of renal cell carcinoma?
Tumour thrombus extending into the inferior vena cava
What is the typical sonographic appearance of the renal sinus in cases of renal vein thrombosis?
Markedly compressed by the swollen parenchyma
What is the underlying pathophysiology of the sonographic appearance of the kidney in cases of renal vein thrombosis?
Swelling of the parenchyma
Study Notes
Renal Vein Thrombosis
- Most commonly associated with membranous nephropathy, producing the nephrotic syndrome
- Also associated with systemic lupus erythematosus, diabetes, glomerulonephritis, hypovolaemic shock, and renal transplantation
- Abnormalities of coagulation, involving clotting factors, the fibrinolytic system, and platelets, can be demonstrated
- Dehydration more commonly associated with renal vein thrombosis in infants, but may occur in adults, particularly in hot climates
- Renal cell carcinoma may invade the renal vein and produce a tumour thrombus, which can extend into the inferior vena cava (IVC) and provide a source of emboli
Ultrasound Imaging of Renal Vein Thrombosis
- Sudden complete occlusion of the main renal vein produces an enlarged, echo-poor kidney
- Changes develop over the initial 24 hours, due to swelling of the parenchyma
- Echo-free areas of haemorrhagic infarcts can be distinguished within the generally echo-poor tissue
- Renal sinus echoes may be markedly compressed by the swollen parenchyma
- After 10–14 days, the kidney starts to shrink, resulting in a small kidney with abnormally high reflectivity
- Corticomedullary differentiation is initially preserved, but is lost after 3–4 weeks as the kidney contracts
Renal Artery Occlusion
- Sudden renal infarction can occur from various causes, including atheromatous plaque haemorrhage, aortic dissection, emboli, and traumatic avulsion
- Unilateral renal artery occlusion does not produce renal failure, and without Doppler, may be difficult to detect with ultrasound
- In the immediate acute stage, the affected kidney may be normal in size and have normal reflectivity, but a small increase in size compared with the perfused contralateral kidney may be demonstrated
- In some patients, a subcapsular ‘halo’ or rim of echo-poor tissue can be seen, which is thought to correspond to oedematous perfused tissue fed by capsular collateral vessels
- In the longer term, the affected kidney slowly shrinks with smooth margins and no dilatation of the collecting system
Medullary Changes and Corticomedullary Differentiation
- Medullary pyramids may be more prominent in many cases of parenchymal disease, due to increased cortical reflectivity
- In acute conditions involving primarily the medulla, such as acute tubular necrosis, the pyramids can be enlarged due to oedema
- Increased medullary reflectivity can be detected in nephrocalcinosis of any etiology and also in some other conditions such as gout
Vascular Disorders
- Renal vein thrombosis may be seen in up to 40% of septic or dehydrated infants
- Acute presentation with renal vein thrombosis is rare in adults, but when it does occur, it is generally unilateral or restricted to one segment and clinical renal failure does not occur
This quiz covers the causes and associations of renal vein thrombosis, including membranous nephropathy, systemic lupus erythematosus, and more. Test your knowledge of ultrasound imaging in this field.
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