Urethral extensibility applied to reconstructive surgery

The human male urethra has great capacity to extend under traction. This extensibility is the principle of some surgical techniques used to overcome urethral defects and for penile lengthening. However, to our knowledge safe limits of urethral extensibility in reconstructive surgery have not been yet established by a morphological study. To this end we measured fresh human cadaveric urethras with and without traction.

We analyzed the macroscopically normal, fresh cadaveric urethra from 25 men 6 months to 73 years old at death (mean age 30.6). Penile length and length of the total, penile, bulbar and membranous urethra were measured. Length under maximal constant traction and the maximal stretched length without penile curvature at artificial erection were determined. Extensibility is expressed as the percent of the variation in initial length at rest and maximal constant traction length. Maximal stretched length without penile curvature at artificial erection is expressed as a percent of maximal constant traction length.

Total urethral extensibility was higher than penile extensibility (p <0.001). Urethral extensibility decreased with aging (r = -0.806, p <0.001). Mean extensibility of the whole male urethra was 66.2% +/- 7.2% and differences among urethral segments were not significant (p = 0.283). Mean maximal stretched length without penile curvature at artificial erection was 75.2% +/- 3.8% and it did not change with age.

Knowledge of the safe anatomical limit of urethral extensibility applied to reconstructive surgery may avoid complications and the necessity for more complex techniques. This limit should be approximately 75% of the maximal constant traction length or a gap-to-normal urethra ratio of 1:4. However, age related variations should be considered.