Recently, attention has focused on the vesical adaptation response to diuresis (VARD). When urine output increases, voided volume at each voiding also increases in normal subjects. This is generally understood as the VARD. It has been indicated that the VARD is lacking in overactive bladder (OAB). On the other hand, male lower urinary tract symptoms (male LUTS) secondary to bladder outlet obstruction (BOO) are common and interfere with the quality of life (QOL) of elderly men. Most male LUTS patients report OAB symptoms. Current oral therapies for male LUTS recommended by guidelines include α-adrenoceptor antagonists (α-blockers, ABs) and 5α-reductase inhibitors (5ARIs). Some studies reported that AB or 5ARI monotherapy did not improve OAB symptoms of male LUTS patients sufficiently. It was suggested that muscarinic receptor antagonists (MRAs) or β3-adrenoceptor (β3-AR) agonist add-on therapy to the drug was effective for some patients with residual OAB symptoms. However, useful predictors of add-on therapy improving OAB symptoms in male LUTS patients remain unclear. The aim of this study was to determine whether the VARD can be used to predict the efficacy of add-on therapy for OAB symptoms in men treated for LUTS.

Men with LUTS who had residual OAB symptoms despite treatment with ABs or 5ARIs and received add-on therapy (MRAs or β3-AR agonist) for one year were included in this study. OAB was evaluated using the Overactive Bladder Symptom Score (OABSS). Residual OAB was defined as an OABSS total score greater than 3 and an urgency score greater than 2 before add-on therapy. Uroflowmetry, ultrasonography to measure the prostate volume, and 24-h frequency-volume charts (FVCs) were evaluated before and one year after add-on therapy. The 24-h frequency-volume chart (FVC) recorded the volumes voided, as well as the time of each micturition. The urine output rate was calculated by dividing the volume voided by the interval between 2 successive micturitions. According to the changes in OABSS between before and after add-on therapy, the patients were divided into two groups: the improvement group (OABSS decreased less than 2 after add-on therapy); and the no-improvement group (OABSS 2 or greater after add-on therapy). The association between the urine output rate and voided volume at each voiding was analyzed in each group. P-values <0.05 were considered significant.

A total of 10 patients entered the study (improvement group 5 patients, no-improvement group 5 patients). Before add-on therapy, age, prostate volume, maximum urinary flow rate, and residual urine volume were not significantly different between the two groups. There was no significant correlation between the urine output rate and voided volume at each voiding before add-on therapy in the improvement group (urine output rate 78.15 ± 5.5 mL/h, voided volume 131.04 ± 6.32 mL, P=0.15, C.C=0.16). In the no-improvement group, the urine output rate was significantly associated with each voided volume before add-on therapy (urine output rate 90.60 ± 8.92 mL/h, voided volume 133.3 ± 6.22 mL P<0.01, C.C=0.34). After add-on therapy, there was a significant association between the urine output rate and voided volume at each voiding in each group (the improvement group: urine output rate 78.29 ± 5.80 mL/h, voided volume 131.09 ± 6.32 mL, P<0.01, C.C=0.49, the no-improvement group: urine output rate 53.17 ± 7.29 mL/h, voided volume 127.90 ± 5.97 mL, P<0.01, C.C=0.34).

The VARD was defined as the presence of a significant correlation between the urine output rate and voided volume at each voiding. In the present study, patients in the improvement group did not show the VARD before add-on therapy, but they showed the VARD after add-on therapy. On the other hand, patients in the no-improvement group showed the VARD before and after the add-on therapy. These results suggest that the add-on therapy ameliorates residual OAB symptoms of male LUTS patients by improving the VARD.

The VARD may contribute to maintaining OAB symptoms of male LUTS patients despite treatment with ABs or 5ARIs. The VARD may be a useful predictor of the efficacy of add-on therapy for OAB symptoms in men treated for LUTS.