Anatomical study of the prostatic urethra using vinyl polysiloxane casts.

BACKGROUND

There are limited studies describing the detailed nonhistologic anatomy of the prostatic urethra. We studied radical prostatectomy specimens to describe the ex vivo anatomical details of its shape and size.

METHODS

We conducted an observational study examining the prostatic urethra anatomy. Prostatic urethra casts (molds) were made using vinyl polysiloxane immediately after fresh specimens had been retrieved following prostatectomy for organ-confined prostate cancer. The following measurements were taken from the casts: anterior length, posterior length, maximal diameter, bladder neck to verumontanum, verumontanum to apex length, and prostate urethral angle (PUA). Prostate volume was calculated using the ellipsoid formula: ((p/6) × transverse × length × height).

RESULTS

Thirty-three prostatic urethral casts were obtained. The mean prostate volume was 38.59 cc. The mean PUA was 127.6°. The mean transverse, apex, and length of the prostate were 4.65, 4.06, and 3.63 cm, respectively. The mean distance from the verumontanum to sphincter was 1.2 cm. The ratio between the anterior and posterior length of the prostatic urethra was 0.82 cm and did not correlate with prostatic size (Figure 8).

CONCLUSION

The distance from the verumontanum to the apex does not change with prostate size; it is uniform with a mean length of 1.2 cm. The anterior length, posterior length, and maximum diameter of the prostatic urethra increase with prostate size. The mean difference between the anterior and posterior length is 0.8 cm and did not correlate with prostate size. Urethral angulation decreased with prostate size but was not significant. Information obtained from this study is of value designing prostatic stents and devices for benign prostatic hyperplasia.