Renal vein thrombosis with inferior vena cava extension in PLA2R-positive membranous nephropathy: A radiological mimic of acute pyelonephritis

Renal vein thrombosis (RVT) is a recognized but often underdiagnosed complication of nephrotic syndrome, particularly in membranous nephropathy. We report the case of a 37-year-old male with PLA2R-positive membranous nephropathy who developed complete thrombosis of the left renal vein with extension into the inferior vena cava (IVC) over a length of approximately 5 cm. Contrast-enhanced computed tomography (CECT) demonstrated poor enhancement of the left kidney with extensive perinephric and periureteric fat stranding, closely mimicking acute pyelonephritis. Laboratory evaluation revealed massive proteinuria (∼12 g/d) with no clinical or laboratory evidence of infection. The patient was treated with anticoagulation and immunosuppressive therapy (modified Ponticelli regimen), with subsequent clinical improvement. This case highlights an important diagnostic pitfall and underscores the importance of clinico-radiological correlation.