Introduction

Several studies have shown penile shortening after Radical prostatectomy (RP); however, the underlying mechanism of this phenomenon is not well-elucidated. In the current study, chronological changes in penile length (PL) before and after RP were measured and the underlying mechanisms were investigated for the same.

Methods

Stretched PL (SPL) of 102 patients was measured before, 10 days after, and at 1, 3, 6, 9, 12, 18, and 24 months after RP. The perpendicular distance from the distal end of the membranous urethra to the midline of the pelvic outlet was measured on mid-sagittal magnetic resonance imaging (MRI) slice at three time-points: preoperatively, 10 days after RP and 12 months after RP. Pre- and postoperative SPLs were compared using paired Student’s t-test. Predictors of PL shortening at 10 days and at 12 months after RP were evaluated on univariate and multivariate analyses.

Results

The SPL was shortest at 10 days after RP; it gradually recovered thereafter (Fig.1). SPL at 12 months after RP was not significantly different from preoperative SPL. On MRI examination, the distal end of membranous urethra was found to have moved proximally (mean proximal displacement: 3.9 mm) at 10 days after RP, and to have returned to the preoperative position at 12 months after RP. Only the volume of the removed prostate was a predictor of SPL change at 10 days after operation on univariate analysis; on multivariate analysis, the association was not statistically significant. No predictor of SPL change was shown at 12 months after RP.

Conclusions

The SPL was shortest at 10 days after RP and gradually recovered thereafter in this study. Anatomically, glans and corpus spongiosum surrounding urethra is an integral structure, and the proximal urethra is drawn into pelvis during urethrovesical anastomosis (Fig.2). This is the first report showing that slight vertical repositioning of the membranous urethra after RP causes chronological changes in SPL. The information is useful for patients to know penile appearance changes after RP.

Funding

none