BACKGROUND The main objectives of bladder substitution are the preservation of the upper urinary tract and maintenance of urinary continence. Orthotopic bladder substitution makes it possible to achieve urinary continence as well as normal passage of urine through the urethra. Creation of a low pressure reservoir and careful preservation of the distal sphincter mechanism are considered to be of utmost importance for the maintenance of urinary continence after orthotopic bladder substitution. However, sphincter behavior after orthotopic bladder substitution has not been fully elucidated. The purpose of this study was to evaluate the vesicourethral continence mechanism after orthotopic bladder substitution in male patients. METHODS Urodynamic evaluation was performed in 14 male patients after cystoprostatectomy for bladder cancer and an ileocolic neobladder using a cecourethral anastomosis. RESULTS Good continence was achieved in 86% (12/14) of the patients during the day and in 79% (11/14) at night. On cystometry, maximum capacity of the neobladders was 434 +/- 21 ml (mean +/- SEM), and basal pressure at maximum capacity was 15.6 +/- 0.9 cm water. Phasic neobladder contraction with amplitudes ranging from 14 to 40 (26.6 +/- 2.7) cm water were noted in 11 of 14 patients. Sphincter electromyography demonstrated an increase in the frequency of action potentials of the external urethral sphincter during neobladder filling from empty to 80% of capacity (from 8.9 +/- 1.6 to 14.6 +/- 2.1 spikes per second; mean percentage increase, 64%, in patients with daytime continence). Maximum urethral closure pressure on urethral pressure profile was 49.9 +/- 3.5 (range, 30 to 64) cm water in patients with daytime continence, while in two patients who were incontinent during the day and at night maximum urethral closure pressure was lower (16 and 24 cm water) and the recruitment of action potentials of the external urethral sphincter during neobladder filling was impaired (percentage increase, 15% and 20%). CONCLUSIONS An ileocolic neobladder has characteristics of a low pressure reservoir with a satisfactory continence rate. The vesicourethral continence reflex is well preserved in patients with continence after orthotopic bladder substitution.