Renal Vein Thrombosis
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Direct answer
Renal vein thrombosis is obstruction of the renal vein by clot, most often seen in adults with nephrotic syndrome, classically due to membranous nephropathy. It causes flank pain, haematuria, a tender enlarged kidney and sometimes acute kidney injury or pulmonary embolism. Doppler ultrasound is the first-line test, with CT or MR venography to define the thrombus. Treatment is anticoagulation, starting with heparin and continuing with an oral anticoagulant.
What you must remember
- Membranous nephropathy: the classic cause of renal vein thrombosis in adults.
- Hypercoagulable state: urinary loss of antithrombin and raised fibrinogen promote clotting in nephrotic syndrome.
- Presentation: flank pain, gross haematuria, a tender enlarged kidney and falling urine output.
- Laboratory clues: worsening proteinuria and a rising creatinine in a nephrotic patient.
- First imaging: Doppler ultrasound, followed by CT or MR venography for extent.
- Anticoagulation: heparin first, then warfarin or another oral anticoagulant for several months.
- Other causes: renal cell carcinoma with tumour thrombus, dehydration in infants, lupus and amyloidosis.
Diagnosis and management pathway
A middle-aged man with membranous nephropathy develops sudden flank pain, gross haematuria and a falling urine output. Renal vein thrombosis is easy to miss when it is attributed to infection or the nephrotic process, so the examiner expects the thrombosis to be considered first. The steps below show how to confirm it and plan treatment.
- Suspect it in nephrotic syndrome: consider renal vein thrombosis when a nephrotic patient presents with flank pain or haematuria.
- Image promptly: Doppler ultrasound comes first, followed by CT or MR venography to define the extent of the clot.
- Look for tumour: exclude renal cell carcinoma with tumour thrombus, especially in an older adult with a renal mass.
- Start heparin: anticoagulate with unfractionated or low-molecular-weight heparin, then continue with an oral agent.
- Plan the duration: continue anticoagulation for several months, and longer while nephrotic syndrome persists.
- Treat the kidney disease: address the underlying nephrotic condition, and monitor renal function and potassium.
Renal vein thrombosis is a treatable complication when recognised early. The nephrotic state keeps the clotting risk high, so the duration of anticoagulation depends on the underlying disease.
Where the exam tests renal vein thrombosis
Questions here test whether you think of the thrombosis and treat it rather than avoid anticoagulation.
- Trap: assuming flank pain and haematuria in nephrotic syndrome is just infection Correct: renal vein thrombosis is common in membranous nephropathy, so it must be considered and imaged.
- Trap: withholding anticoagulation because of haematuria alone Correct: renal vein thrombosis needs anticoagulation with monitoring for bleeding.
- Trap: ignoring a renal mass when thrombosis appears in an older adult Correct: renal cell carcinoma can extend into the renal vein, so imaging must look for a tumour.
Frequently asked questions
Which kidney disease is most commonly linked to renal vein thrombosis in adults?
Membranous nephropathy is the disease most commonly linked to renal vein thrombosis in adults. Its nephrotic state creates a hypercoagulable tendency, and the risk is greatest when serum albumin is very low.
What are the typical presenting features of renal vein thrombosis?
Renal vein thrombosis typically presents with flank pain, gross haematuria, a tender enlarged kidney and sometimes acute kidney injury. Pulmonary embolism may occur because part of the clot can embolise.
Which imaging confirms renal vein thrombosis?
Doppler ultrasound is the first-line test for renal vein thrombosis, and CT or MR venography defines the extent of the thrombus. Renal venography is used less often today but remains a definitive method.
How long should anticoagulation continue after renal vein thrombosis?
Anticoagulation after renal vein thrombosis usually continues for several months, with heparin followed by an oral anticoagulant. It is extended when nephrotic syndrome persists, because the hypercoagulable state continues.