A 45-year-old man with biopsy-proven idiopathic membranous nephropathy and nephrotic syndrome presents with sudden severe left flank pain radiating to the groin, visible haematuria, and a fall in haemoglobin from 13.5 to 10.2 g/dL. Blood pressure is 105/65 mmHg. CT abdomen shows an enlarged left kidney. What is the most likely diagnosis?
- A Renal infarction from thromboembolism
- B Renal vein thrombosis ✓
- C Left ureteric calculus with obstruction
- D Perinephric abscess
Correct answer: B. Renal vein thrombosis
Explanation
Membranous nephropathy carries the highest risk among glomerulonephritides of renal vein thrombosis, driven by urinary loss of antithrombin III and other natural anticoagulants. Flank pain with visible haematuria, falling haemoglobin from haemorrhage into the parenchyma, and an enlarged kidney are classic. Ureteric calculus typically causes colicky pain without nephromegaly or significant haemoglobin drop, and renal infarction presents with pain but usually without a large congested kidney on imaging.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.