Transureteroureterostomy obstruction mimicking acute tubular necrosis

A patient receiving nephrotoxic chemotherapy for metastatic cervical cancer was examined for acute renal failure. A Tc-99m MAG3 scan showed symmetric function, bilateral increasing parenchymal activity, and no tracer excretion in either collecting system. The differential diagnosis included cisplatin-induced nephrotoxicity, dose infiltration, and obstruction of the common ureter. Analysis of the scan, an image over the injection site, and a delayed image of the urinary tract indicated obstruction of the common ureter at the anastomotic site of the transureteroureterostomy. In patients with a transureteroureterostomy, symmetric renal dysfunction, and no bladder activity, a delayed image of the urinary tract should be obtained to distinguish obstruction from acute tubular necrosis.