Objectives: To investigate whether detrusor overactivity (DO) and the response to the ice water test (IWT) influence nighttime urinary frequency in patients with lower urinary tract symptoms.
Methods: A total of 114 patients with lower urinary tract symptoms, who were older than 50 years, with an International Prostate Symptom Score 8 or more points and a quality of life index of 2 or greater, were evaluated by a 48-hour frequency-volume chart, free flowmetry, pressure flow study, and IWT.
Results: The DO-positive IWT responders had a significantly greater bladder outlet obstruction index than did the DO-positive IWT nonresponders and the DO-negative IWT nonresponders. The DO-positive IWT responders had significantly more frequent nocturia and smaller nighttime maximal and minimal voided volumes than did the DO-negative IWT nonresponders without any difference in the nocturnal voided volume. The patients with nocturia two or more times had a significantly larger nocturnal voided volume and smaller nighttime minimal voided volume than the patients with nocturia less than two times. The incidence of DO-positive IWT responders was significantly greater among the patients with nocturia three or more times than that among those with nocturia less than three times. In the multivariate logistic model, the nocturnal voided volume and nighttime minimal voided volume were independently associated with nocturia two or more times and the DO-positive IWT responders were independently associated with nocturia three or more times.
Conclusions: Once high-grade bladder outlet obstruction induces C-fiber-related DO, it is strongly suggested that this process, together with nocturnal polyuria, plays an important role in the consequent clinical manifestations of nocturia in patients with lower urinary tract symptoms.