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Introduction: Underactive bladder (UAB) is a symptom complex of voiding difficulty. Detrusor underactivity (DU) is the urodynamic observation of insufficient voiding detrusor pressure. Impaired contractility implies detrusor failure. While these terms are often used synonymously, the degree of association is unknown. Objective: to compare urodynamic sensory and motor functions between UAB and DU.
Materials & Methods:198 urodynamic charts were abstracted with IRB approval. Primary symptoms classified as overactive bladder (OAB), underactive bladder (UAB) and Incontinence (UI). Primary urodynamic findings were volume hypersensitivity without detrusor overactivity (VH), detrusor overactivity (DO), stress urinary incontinence (SUI), outlet obstruction (BOO), dysfunctional voiding (DV), detrusor underactivity (DU). Volumes at First Sensation (FS), First Desire (FD), Normal Desire (ND), and Strong Desire (SD) were recorded. Maximum Watts factor (WF), age, sex, and postvoid residual volumes (PVR) were recorded. Means were compared with ANOVA. Contingency tables were analyzed. Correlations were sought among continuous variables.
Results: 59 patients had a primary symptom of UAB, 27 of DU. UAB and DU were associated with higher volume sensory thresholds than non-UAB, non-DU. Both had larger PVRs than other symptoms/findings. No significant differences among symptom and observation groups were found for WF. UAB as a predictor of DU is 22% sensitive, 89% specific.
Conclusions: UAB and DU are associated with increased PVR without necessary loss of contractility. UAB does not require DU. Diminished volume sensitivity characterizes UAB and may relate to the etiology of DU. UAB, DU and impaired contractility are distinct concepts, and the terms are not interchangeable.