[An urodynamic study on neobladder function].

OBJECTIVE To analyze the urodynamic characteristics of neobladders, we conducted a pressure-flow study in patients with orthotopic urinary reservoirs. PATIENTS AND METHODS From 1986 to 1996, 90 patients underwent bladder replacement following cystectomy, using a right colonic, ileocolic, ileal, or sigmoid colonic segment. The subjects were 38 patients (31 men and 7 women) with stable urination and no evidence of cancer recurrence, urethral stricture, urinary tract infection or vesicoureteral reflux. Their mean age was 60.5 years, with a range of 38 to 77 years. Information on neobladder function, such as desire to void, force of micturition, urinary incontinence and other complaints, was obtained by questionnaire. A pressure-flow study was performed in all patients 3 months to 103 months postoperatively to evaluate total reservoir pressure, abdominal pressure and subtracted reservoir pressure during filling and voiding phases. RESULTS Ten of 38 patients (26.3%) were dissatisfied with their neobladder function, due to weakness of urinary sensation, loss of urinary force and enuresis. In 6 of the 7 patients with enuresis, the urinary reservoir had been created by Heineke-Mikulicz's procedure of detubularization; 4 of these patients had a high degree (over 40 cmH2O) of phasic contraction during the filling phase. In only 2 of the 38 patients, a pressure-flow study showed an almost same pattern as that obtained with a normal urinary bladder. Twelve patients had increased electromyogram of the external urethral sphincter during the voiding phase, while half of the 38 patients showed a flat electromyogram during both the filling and voiding phases. Thus, 31 of 38 patients revealed a sphincter dyssynergia pattern. Mean total reservoir pressure at maximum cystometric capacity was 65.5 +/- 42.1, 48.4 +/- 19.0, 66.0 +/- 61.0 and 107.0 +/- 43.3 cmH2O in ileal, ileocecal, right colonic and sigmoid neobladders, respectively. The value for sigmoid neobladder was statistically different from that for ileocecal neobladder (p < 0.05). Mean total reservoir pressure at maximal flow was 73.1 +/- 42.4, 56.4 +/- 22.6, 88.9 +/- 69.4 and 94.0 +/- 31.8 cmH2O in ileal, ileocecal, right colonic and sigmoid neobladders, respectively. There were no statistically significant differences among these values. The ratio of subtracted reservoir pressure to total reservoir pressure was lower at maximal flow than at onset. Subtracted reservoir pressure may contribute to total reservoir pressure to a greater extent in sigmoid neobladders than in other types of neobladder. CONCLUSIONS 1. Enuresis may have various causes such as external sphincter dysfunction and involuntary contraction of the reservoir. 2. Urine is evacuated not only by abdominal pressure but also by subtracted reservoir pressure in neobladders. 3. Sphincter dyssynergia due to absence of the detrusor muscle may be one cause of dysuria.