Association Between Preoperative Penile Circumference and Urinary Function After Robot-Assisted Radical Prostatectomy.

This study investigated whether preoperative penile length, penile circumference, and testis size are associated with urinary function and sexual function after robot-assisted radical prostatectomy (RARP). We retrospectively analyzed 197 Japanese patients who underwent RARP. Patients were categorized based on the median preoperative penile length, penile circumference, and testis size. Urinary function and sexual function were assessed based on the daily pad usage and the results of the Expanded Prostate Cancer Index Composite (EPIC), International Prostate Symptom Score (IPSS), and International Index of Erectile Function-5 (IIEF-5) questionnaires preoperatively and 1, 3, 6, and 12 months postoperatively. Preoperative penile circumference was significantly associated with postoperative urinary outcomes. The thick penis group (larger than the median preoperative penile circumference) used fewer daily pads and had better urinary function scores (EPIC and IPSS) compared to the thin penis group (median or smaller preoperative penile circumference) postoperatively. In contrast, preoperative penile length exhibited no significant relationship with postoperative urinary function. Postoperative sexual function scores (EPIC and IIEF-5) showed trends that favored the long (longer than the median preoperative penile length) and thick penis groups than the short (median or shorter preoperative penile length) and thin penis groups, but significant differences were limited to specific time points. Preoperative testis size exhibited no significant relationship with urinary and sexual outcomes. The preoperative penile circumference was associated with urinary function after RARP, highlighting its potential as a practical clinical marker. However, the association between preoperative penile size and sexual function was minimal.