AB284. SPR-11 What’s wrong with underactive bladder patients?

Objective: Underactive bladder (UAB) is receiving increased attention as a contributor to urinary bother. An emerging definition of UAB focuses on voiding symptoms suggestive of urodynamic detrusor underactivity. However, while animal and tissue studies are useful to elucidate pathophysiologic mechanisms, they cannot directly address human symptoms. Objective dysfunctions associated with UAB symptoms remain unclear. We therefore sought to describe the urodynamic observations associated with voiding symptoms consistent with UAB.

Methods: A retrospective review of 500 consecutive urodynamic studies conducted by one urodynamicist in one clinical laboratory. Charts of patients with known neurologic disease, prior bladder or urethral surgery, and charts lacking symptom descriptions were excluded. Age, sex, primary and secondary symptoms, urodynamic variables and observations (UO) were logged. Three groups were identified for analysis and comparison: Primarily UAB symptoms (UAB1), any UAB symptoms (UAB), and no UAB symptoms.

Results: Four hundred and twenty-one charts were suitable for abstraction. Of 132 patients with any UAB, 100 were UAB1. Of the remainder 16 were primarily storage/OAB symptoms, and 14 were primarily Incontinence. Average age of UAB patients was 56±1.5 yrs, vs. 57.4±1.0 for non-UAB (n.s.). UAB1 patients were 59.1±1.8 yrs old vs. 54.7±2.4 yrs for UAB (n.s.). For UAB1 and UAB, BOO was the most common UO, 35/40% of patients having outlet obstruction (BOO), 25/25% had detrusor underactivity (DU), 20/26% were dysfunctional voiders (DV), 12/13% had detrusor overactivity, 5/8% had SUI, and 3/5% had volume hypersensitivity. UAB1 was more prevalent in men, 54m/46f, however overall 76 females vs. 56 males had any UAB. DU was more common in women than men (21f/12m) with UAB, but BOO was more common in men (37m/13f). Overall, UAB had higher volume sensations thresholds than non-UAB (P<0.05), however less consistently for UAB1 and for UAB patients with BOO, DU, or dysfunctional voiding. Watts Factor did not differ by UAB, BOO, or DU, but PVR was greater in UAB1, UAB, BOO and DV patients with UAB vs. nonUAB patients (P<0.05). For DU, PVR in UAB patients was 376±50 vs. 255±37 mL for nonUAB, P=0.06. Patients with BOO and DU were older, but did not differ by age according to the presence/absence of UAB.

Conclusions: Urodynamic observations related to impaired voiding (BOO, DU, DV) but not impaired contractility account for most urodynamic dysfunctions in UAB patients. An elevated PVR and diminished volume sensations contribute to the occurrence of UAB. Animal models of UAB should address the reasons for diminished system sensitivity to bladder volume rather than a limited focus on detrusor motor deficiencies.

Funding Source(s): None

Keywords: Underactive; bladder; human; outlet obstruction; dysfunctional voiding