Sphincter electromyography in patients after radical prostatectomy and cystoprostatectomy

Urethral sphincter weakness may occur after major pelvic surgery and urinary incontinence, either temporary or permanent, may result. In order to determine whether the cavernous nerves described by Donker and Walsh carry fibres to the distal urethral sphincter as well as those supplying the corporal bodies, we have studied prospectively the sphincter electromyography in 2 groups of 10 patients: (1) those who had undergone nerve-sparing radical prostatectomy for prostatic carcinoma and (2) those who has undergone radical cystoprostatectomy for bladder carcinoma. This study group was compared with a control group of normal individuals. The results showed significant differences in duration of motor units between the control group and prostatectomy group and between the control group and cystectomy group but no significant difference between the 2 operated groups. There was no significant difference in amplitude of the motor units, the sacral reflex latencies or the pudendal somatosensory evoked potentials between all 3 groups. It was therefore concluded that division of the cavernous nerve of Walsh does not compromise distal urethral sphincter function. Furthermore, radical transabdominal lower urinary tract surgery may induce significant electromyographic changes in the external sphincter which may not be clinically evident. This may potentially affect continence later if second-stage urinary reconstructive surgery is undertaken.