CT of the urinary tract after abdominoperineal resection for rectal carcinoma.

Computed tomography (CT) after abdominoperineal (AP) resection for rectal carcinoma is a routine procedure for the detection of recurrent tumor and distal metastases. We reviewed sequential CT scans after AP resection in 52 patients in order to see whether the urinary tract as a neighboring organ is involved in recurrent malignancy. Bladder displacement in itself was not associated with hydronephrosis. Such hydronephrosis developed, however, in 14 patients--13 with a presacral mass, and one with retroperitoneal lymphadenopathy. In 23 of the 52 patients a presacral mass appeared, either fibrosis, infection, or recurrence. Severe hydronephrosis was found only with malignancy. We suggest that marked hydronephrosis associated with a presacral mass after AP resection is an indirect sign of malignancy.