Abnormal renal vascular morphology Renal vein thrombosis 2022-04-10T17:38:05Z The presence of a thrombus (blood clot) in the major renal veins or its tributaries, generally leading to passive congestion that develops causes the affected kidney to swell and become engorged, leading to degeneration of nephrons and causing symptoms of flank pain, hematuria, and decreased urine output. Diagnosis can be made by magnetic resonance angiography, Doppler ultrasonography, or computed tomography angiography.