Mechanism of continence after transpubic urethroplasty.

Urethral profilmetry was performed in seven continent patients with transpubic urethroplasty. The studies were repeated in the supine and upright positions, both at rest and under the stresses of cough, bearing down, and hold maneuvers. The urethral pressure tracing of these patients is characteristically bihumped in shape. The proximal hump with a mean height of 18 cm water at rest corresponds to the prostatic plateau of normal subjects. The distal hump with a mean height of 32 cm water represents the pressure inside that segment of the bulbar urethra which had been brought into the abdomen by the transpubic operation. The average functional urethral length is 4.6 cm and on standing increased to 6.7 cm, mainly due to elongation of the distal hump. Changes in intra-abdominal pressure by cough or bearing down are transmitted along the whole functional urethral length with augmented urethral closure pressure of 57 to 61 cm water in the proximal hump and 44 to 48 cm water in the distal hump. However, contraction of the perineal musculature by hold maneuvers has no effect on the urethra of these patients. We conclude that after transpubic urethroplasty, although the distal urethral mechanism is destroyed and excluded, the new intra-abdominal position of the transposed bulbar urethra provides a new factor that supplements the bladder neck in maintaining urinary continence.