Correspondence Weill Medical College of Cornell University, New York Presbyterian Hospital, 525 East 68th Street, Starr 900, New York, NY 10021, USA

Email jpm2005@med.cornell.edu

Original article

Gontero P et al. (2007) New insights into the pathogenesis of penile shortening after radical prostatectomy and the role of postoperative sexual function. J Urol 178: 602–607   PubMed

Synopsis

Background

Progressive penile shortening is a common complaint among men who have undergone radical prostatectomy (RP); however, the pathogenesis of penile shortening in these patients is not clear.

Objectives

The objectives were to assess changes in penile dimensions after RP, and to determine whether recovery of erectile function or nerve-sparing surgery had an effect of penile size.

Design and intervention

This study included patients who were scheduled to undergo retropubic RP for the treatment of organ-confined prostate cancer. Exclusion criteria were previous penile disease or surgery, or previous treatment with neoadjuvant therapy or radiotherapy. Before RP, prostate volumes and diameters were measured using a 7.5 MHz transrectal ultrasound probe. Nerve-sparing surgery was performed in some patients, depending on serum PSA level, tumor location, the number of positive biopsies, preoperative potency and patient age. Penile measurements were taken immediately before surgery (t₀), at catheter removal (t₁), and at 3 (t₂), 6 (t₃) and 12 months (t₄) after surgery. Two physicians obtained penile dimensions; penile length was measured by a taper ruler to the nearest 0.5 cm while the penis was flaccid and maximally stretched, and penile circumference was measured at midshaft. Erectile function was assessed using the erectile function domain of the international index of erectile function (IIEF) before surgery, and at 3, 6 and 12 months after surgery.

Outcome measures

The outcome measures were penile length, penile circumference and erectile function as measured by the IIEF.

Results

The study enrolled 126 patients, of whom 50 received nerve-sparing surgery. Preoperative erectile function was abnormal in 79.37% of patients. Penile measurements were obtained from 123, 117, 114 and 105 patients at t₁, t₂, t₃ and t₄, respectively; missing penile measurements were mainly caused by patients' failure to attend follow-up visits. At t₄, a mean reduction in penile length of 1.34 cm and 2.3 cm in the flaccid and stretched measurements, respectively, was observed. The maximum decrease in penile length occurred between t₀ and t₁, but shortening also occurred during all other time intervals in both the flaccid and stretched states. The mean penile circumference was slightly increased at t₁ compared with t₄, but penile circumference decreased in all subsequent time intervals. Stretched penile length at baseline was the only characteristic that correlated with penile shortening between t₀ and t₁. Between t₀ and t₄, and between t₁ and t₄, patient age, type of surgery, and recovery of erectile function after 1 year were correlated with penile shortening. Nerve-sparing surgery and an IIEF erectile dysfunction value 15 were independent predictors of reduced penile shortening between t₀ and t₄.

Conclusions

After RP, the maximum penile shortening occurs at the time of catheter removal, and continues until at least 1 year after surgery. Nerve-sparing surgery and recovery of erectile function were independent predictors of reduced penile shortening at 1 year post-surgery.

Commentary

While patients often complain about decreased penile length after RP, this issue has received minimal attention compared with other post-RP problems. Excluding this study by Gontero et al., four studies have analyzed penile dimensions after RP.^{1, 2, 3, 4} Three studies found that penile dimensions were reduced after surgery,^{1, 2, 3} and only Briganti et al.⁴ found no difference between preoperative and postoperative penile dimensions.

The literature indicates that permanent structural alterations less than 4 months after surgery are uncommon,⁵ but this study found that maximal penile shortening occurred at catheter removal. Gontero et al. failed to satisfactorily explain the mechanism for such a dramatic length loss in a short period. It could have resulted from the high proportion of non-nerve-sparing surgery performed (60%); my colleagues and I have evidence that the degree of nerve sparing predicts venous leak as well as time to onset of venous leak (J Mulhall, unpublished data). It could also have resulted from reduced force being applied to the penis on the day of catheter removal, which is supported by the increase in penile circumference at this time.

The study also demonstrated that nerve-sparing status and recovery of erectile function were independent predictors of penile length loss 12 months after surgery. This group is the first to demonstrate that erectile function status after surgery is a predictor of penile length loss on multivariate analysis.

Numerous issues need to be considered when measuring the effects of RP on penile morphology. The number of patients investigated is vital—this study included 126 patients and is likely to be adequately powered. The two points utilized to define penile length are also critical. The classic points used are tip of glans and the pubic bone; however, this study used the pubo-penile skin junction, which fails to account for the size of the pre-pubic fat pad. This fat pad might have changed in size during the 12 months after surgery, although it is unlikely to have changed much in the days between surgery and catheter removal. Variations in the technique for measuring penile length between preoperative and postoperative measurement can also affect results. In addition, the person recording penile dimension measurements is key; to limit interobserver variability, one person should do both preoperative and postoperative measurements. In this study, minimal interobserver variability was demonstrated. The examiner(s) should also be blinded to previous penile dimensions, although this point was not commented on in the paper. The ambient environment for penile dimension measurement is critical to outcome, in particular the sex of the assessor and the ambient room temperature. The timing of the measurement postoperatively is also likely to affect results; in this analysis, serial measurement was performed up to 12 months postoperatively. Finally, information about patients' comorbidity should be obtained, but the comorbidity profile was largely unknown in this study. As 80% of patients had erectile dysfunction, we could infer that they were not healthy; however, a low IIEF score does not necessarily indicate an organic etiology. This issue is especially important when we try to extrapolate these data to our individual practices.

These issues notwithstanding, any rigorous assessment of sexual function in the RP population must be applauded, as it is incumbent upon us to define the cause of penile morphologic changes in this population.

Acknowledgments

The synopsis was written by Rachel Murphy, Associate Editor, Nature Clinical Practice.

References

1. Fraiman MC et al. (1999) Changes in penile morphometrics in men with erectile dysfunction after nerve-sparing radical retropubic prostatectomy. Mol Urol 3: 109–115 | PubMed | ISI |
2. Munding MD et al. (2001) Pilot study of changes in stretched penile length 3 months after radical retropubic prostatectomy. Urology 58: 567–569 | Article | PubMed | ISI | ChemPort |
3. Savoie M et al. (2003) A prospective study measuring penile length in men treated with radical prostatectomy for prostate cancer. J Urol 169: 1462–1464 | Article | PubMed | ISI |
4. Briganti A et al. (2007) Preserved postoperative penile size correlates well with maintained erectile function after bilateral nerve-sparing radical retropubic prostatectomy. Eur Urol 52: 702–707 | Article | PubMed |
5. Mulhall JP et al. (2002) Erectile dysfunction after radical prostatectomy: hemodynamic profiles and their correlation with the recovery of erectile function. J Urol 167: 1371–1375 | Article | PubMed | ISI |

Contact the journal about this article

Subject areas under which this article appears: Prostate cancer