ULTRASOUND: Low urine output after renal transplant
Case Author: Deborah Rubens, MD, University of Rochester
History
61-year-old man who has undergone hepatic and renal transplants and has worsening renal function. Ultrasound has been performed, and the next step must be determined.
Imaging Findings
Transverse color Doppler image with spectral tracing obtained postoperatively on day of transplant (TXP) (A) shows a high-resistance arterial waveform. Sagittal color and spectral Doppler image (B) with sampling through the main renal vein (MRV) shows normal color and spectral flow. Transverse color and spectral image (C) 24 hours after B shows a high-resistance waveform with transiently reversed diastolic flow (arrow). Transverse color Doppler image through the renal hilum at a very low scale (D) shows arterial flow but no color in the main renal vein (arrow). SAG = sagittal, MRA = main renal artery.
Diagnosis
Need for return ot the operating room
Teaching Points
The normal arterial waveform in a renal graft has continuous forward flow through diastole with a resistive index of 0.7 or less. A high-resistance waveform (> 0.7) is a nonspecific indicator of increased parenchymal resistance and may have an intrinsic cause (rejection, infection, or acute tubular necrosis) or an extrinsic cause (outflow obstruction of either blood or urine or extrinsic compression).
Doppler imaging in the immediately posttransplant period should identify both arterial inflow and venous outflow in the allograft and perfusion throughout the organ parenchyma.
Although acute tubular necrosis and hyperacute rejection can cause high resistance with reversed flow in diastole, the renal vein flow should still be preserved.
Lack of flow in the renal vein, especially if present in previous studies, indicates one of two causes: renal vein thrombosis or extrinsic compression, both of which require immediate return to the operating room to salvage the allograft. Repeat imaging or imaging with other modalities is unnecessary once the diagnosis has been established.
Suggested Readings
Brown ED, Chen MY, Wolfman NT, Ott DJ, Watson NE Jr. Complications of renal transplantation: evaluation with US and radionuclide imaging. RadioGraphics 2000; 20:607–622
Irshad A, Ackerman SJ, Campbell AS, Anis M. An overview of renal transplantation: current practice and use of ultrasound. Semin Ultrasound CT MR 2009; 30:298–314
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