OBJECTIVE To determine if transrectal ultrasonography (TRUS) is as reliable as cystography in detecting vesico-urethral extravasation (VE) after radical retropubic prostatectomy (RRP). PATIENTS AND METHODS Between October 2005 and February 2006 we prospectively investigated 100 consecutive patients undergoing RRP. The vesico-urethral anastomosis was assessed 6 days after RRP by a combined investigation with TRUS and cystography. RESULTS In most patients (79%), at 6 days after RRP the vesico-urethral anastomosis was watertight or showed minimal leakage (8%), so that the urinary catheter was removed. Different degrees of VE were detected in 21 patients. Because of small, moderate or marked VE, the indwelling catheter remained until 9, 14 and 21 days after RRP in five, three and five patients, respectively. Every VE documented by cystography was detected by TRUS beforehand; therefore TRUS showed no false-negative results in detecting a leaking anastomosis. In two patients paraurethral fluid was detected by TRUS mimicking VE, with no confirmation by cystography. CONCLUSIONS TRUS can safely replace cystography for detecting anastomotic leakage after RRP. The decision to remove the catheter after RRP can be made without radiation exposure and use of expensive contrast medium.