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Renal Vein Thrombosis AT-III Loss Mechanism — ESENeph MCQ

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HardGlomerulonephritisRenal Vein Thrombosis AT-III Loss MechanismESENeph

A 44-year-old man with nephrotic syndrome from membranous nephropathy develops sudden-onset left flank pain with macroscopic haematuria. CT with contrast shows a filling defect in the left renal vein. His albumin is 15 g/L. What pathophysiological mechanism MOST directly causes renal vein thrombosis in nephrotic syndrome?

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Correct answer: D — Antithrombin III loss in urine exceeding hepatic synthesis

The prothrombotic state in nephrotic syndrome results from a complex imbalance: (1) URINARY LOSS of anticoagulant proteins — antithrombin III (62 kDa, heavily lost in urine as it is freely filtered at the size of nephrotic proteinuria), protein C, and protein S; (2) HEPATIC OVERPRODUCTION of procoagulant factors — fibrinogen, factors V, VIII, and vWF (as part of the non-specific hepatic synthetic response to hypoalbuminaemia); (3) Hyperviscosity from haemoconcentration; (4) Platelet hyperaggregability. The loss of antithrombin III is considered the most critical single factor, as AT-III is the primary physiological inhibitor of thrombin and factors Xa, IXa. Renal vein thrombosis is most common in membranous nephropathy specifically.

Reference: KDIGO 2021 – Glomerular Diseases; Kerlin et al 2012 – Thrombosis in Nephrotic Syndrome