Identifying occult bladder outlet obstruction in women with detrusor-underactivity-like urodynamic profiles

Voiding dysfunction can result from detrusor underactivity (DU), bladder outlet obstruction (BOO), or both. Conceptually, women with high-pressure low-flow urodynamic profiles are diagnosed with BOO without DU. However, the possibility of BOO is often neglected in women with DU-like (low-pressure low-flow) urodynamic (UDS) profiles. By reviewing the videourodynamic studies (VUDS) of 1678 women, our study identified the key factors suggesting urodynamic BOO (determined by radiographic evidence of obstruction) in women with DU-like UDS profiles (Pdet.Qmax < 20 cmH2O and Qmax < 15 mL/s). In 355 women with DU-like UDS profiles, there were 70 (19.7%) with BOO and 285 (80.3%) without BOO. The BOO group had predominantly obstructive symptoms. The BOO group showed significantly decreased bladder sensation, lower detrusor pressure (Pdet.Qmax), lower flow rate (Qmax), smaller voided volume, and larger post-voiding residual (PVR) compared to the non-BOO group. In multivariate analysis, volume at first sensation, Qmax, PVR, and detrusor overactivity (DO) remained independent factors for BOO. The receiver operating characteristic (ROC) areas for the parameters were largest for PVR (area = 0.786) and Qmax (area = 0.742). The best cut-off points were 220 mL for PVR and 4 mL/s for Qmax. Our findings provide simple indicators for BOO in women with DU.