Etiology of nocturia response in men with diminished bladder capacity.

Aims: To test the hypothesis that patients with nocturia owing to diminished global or nocturnal bladder capacity improve via increased bladder capacity.
Methods: This is a retrospective analysis of voiding diaries completed at a VA urology clinic between 2008-2017. Inclusion required patients aged at least 18 years, male, undergoing treatment for nocturia, and having completed at least two 24-hour voiding diaries ≥1 month apart. Patients were divided into two cohorts: responders (any decline in nocturia) and non-responders (no change or any increase in nocturia). Patients were further sub-stratified as having low global bladder capacity (maximum voided volume [MVV] <200 mL) versus low nocturnal bladder capacity (nocturnal maximum voided volume [NMVV] <200 mL and MVV ≥200 mL). Wilcoxon rank-sum was applied with a Bonferroni correction to test significance.
Results: Forty pre- and post-treatment diaries from 27 patients, and 19 pre- and post-treatment diaries from 17 patients were identified as having low global and low nocturnal bladder capacity, respectively. Nocturia responders with low global bladder capacity demonstrated significant decline compared to non-responders in nocturnal urine volume (NUV) (-140 vs +75, P < 0.01) and nocturnal bladder capacity index (NBCi) (-0.59 vs +0.23, P < 0.01). Patients with low nocturnal bladder capacity similarly demonstrated decreased NUV (-30 vs +160, P = 0.04) and NBCi (-1.4 vs +0.33, P < 0.01). There was no significant change in MVV or NMVV for either group.
Conclusions: Treatment directed at lowering nocturnal urine production and enabling patients to consistently void at capacity is a rational strategy to treat nocturia in patients with low bladder capacity.
(© 2018 Wiley Periodicals, Inc.)