A 38-year-old man with biopsy-proven primary membranous nephropathy presents with sudden left flank pain and a fall in urine output. Doppler ultrasonography shows an echogenic filling defect in the left renal vein with absent flow. This complication occurs most commonly with membranous nephropathy because:
- A It is associated with the highest magnitude of hypoalbuminemia among nephrotic disorders
- B PLA2R antibodies cross-react with venous endothelium
- C Loss of antithrombin III in urine creates a hypercoagulable state when serum albumin falls below about 2 to 2.5 g/dL ✓
- D Subendothelial immune deposits activate the contact pathway of coagulation
Correct answer: C. Loss of antithrombin III in urine creates a hypercoagulable state when serum albumin falls below about 2 to 2.5 g/dL
Explanation
Urinary loss of antithrombin III (along with proteins B and S) combined with increased hepatic fibrinogen synthesis and platelet hyperaggregability makes nephrotic syndrome hypercoagulable, and renal vein thrombosis is classically most frequent in membranous nephropathy. Deposits in membranous nephropathy are subepithelial, not subendothelial, so option D is anatomically wrong, and PLA2R antibodies are directed against the podocyte antigen itself rather than endothelium.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.