Effects of α-adrenergic agonist on neobladder water and electrolyte transport

Objective. Nocturnal urinary incontinence and nocturia are problematic for patients with continent neobladders. Clonidine, an a2-adrenergic agonist, increases water absorption across rabbit ileum; human intestine contains a substantial density of α²-adrenergic receptors. We studied the effect of neobladder clonidine instillation and catheterization (to reduce urine-bowel contact time) on nocturnal water and electrolyte reabsorption. Methods. A total of 8 patients with Indiana neobladders constructed after radical cystectomy were studied at a mean of 11.3 months postoperatively under standardized diet and fluid intake. Results. Topical clonidine or catheterization failed to alter nocturnal urine volume, freewater clearance, or absolute excretions of electrolytes in Indiana neobladders; however, the absolute excretion of urine urea nitrogen and osmoles was significantly increased in the catheterized urine collections compared with the baseline urine collections (paired t-test, p = 0.0022 and 0.0091, respectively). Conclusions. Bowel comprising neobladders loses its capacity to significantly alter urinary electrolyte composition by prolonged contact, which may explain the rarity of significant acid-base disturbances in patients with continent neobladders. Unfortunately, topical clonidine does not diminish nocturnal urine volumes, but increased excretion of urea and osmoles with overnight neobladder catheterization may prove beneficial in patients who suffer azotemia or hyperosmolarity.