May coexisting overactive-underactive bladder (COUB) be due to muscle fatigue? Data from a single-centre urodynamic database

the ICI-RS has proposed the definition of COUB (coexistent overactive-underactive bladder) as a syndrome characterized by voiding and filling LUTS in the same patient. the aim of this study is to explore whether the presence of DO can lead to DU, because of muscle asthenia and fatigue of the smooth muscle cells. retrospectively, we included all consecutive male patients with LUTS who underwent an invasive UDS (January 2011-december 2022). patients with neurologic diseases or with previous LUT surgery were excluded. they were divided into normal detrusor function, group A and detrusor overactivity, group B during the filling phase. BOOI, BCI, PVR and BVE were compared in the two groups. DO patients were divided according to the phasic or terminal DO contractions and mean BCI was calculated in these subgroups. we analysed 425 male patients with LUTS. during filling phase, 167 patients (39.3%, group A) showed NDF and 258 patients (60.7% group B) DO. 207 of them (80.2%) had phasic detrusor contractions and 51 (20.8%) had terminal DO. MCC was 409.8 mL and 308.7 mL (p<0.0001), respectively. during the voiding phase, 176 patients (41.4) were obstructed, 100 (23.5%) were equivocal and 149 (35.1%) were not obstructed. 179 patients had a BCI <= 100 and 246 (57.9%) >100. 207 (80.2%) patients of the group B showed phasic, while 51 (19.8%) terminal DO; in these subgroups, mean BCI was 118.8 and 112.0 respectively (p 0.806658).