Inefficient urethral milking secondary to urethral dysfunction as an additional risk factor for incontinence after radical prostatectomy

Purpose: Continence after radical prostatectomy is thought to depend comple tely on the striated urethral sphincter. However, some patients complain on ly of occasional post-void dribbling. Therefore, we determined whether uret hral dysfunction may be another cause of incontinence. Materials and Methods: The sensory threshold of electric stimulation was me asured by double ring electrodes in the membranous urethra and 2.5 cm. dist al in 29 men before and in 29 after radical retropubic prostatectomy. In ad dition; voiding cystourethrography was performed in 66 patients before and in 49 after surgery to determine complete post-void urethral emptying or mi lking. Results: The mean sensory threshold of the membranous urethra was 15 +/- 3 mA. preoperatively versus 38 +/- 17 postoperatively (p <0.0001). The sensor y threshold 2.5 cm. further distal was 12 +/- 5 mA. before and 10 +/- 4 aft er radical prostatectomy, which was not statistically significant. Postoper atively in completely, continent patients and in those with dribbling the m ean threshold was 32 +/- 12 and 43 +/- 18 mA. in the membranous urethra (p = 0.09), and 11 +/- 4 and 9 +/- 4 mA. in the bulbar urethra, respectively, which was not statistically significant. Of the 66 patients 36 (55%) showed post-void urethral milking before surgery but only 8 of 49 (16%) showed it postoperatively (chi-square test p <0.0001), including 7 who were complete ly continent and 1 who complained of occasional post-void dribbling. Conclusions: After radical prostatectomy sensitivity of the membranous but not of the bulbar urethra is affected, correlating with postoperative conti nence. In addition, post-void dribbling seems to be associated with the los s of urethral milking. We conclude that preserving urethral function is ano ther important continence factor after radical prostatectomy.