Bladder Contractility Classification Before Bladder Outlet Surgery: Do BCI, Wmax and the Maastricht–Hannover Nomogram Agree and Does It Matter for Outcome?

OBJECTIVES: The aim of this study was to assess the concordance between three classification systems (bladder contractility index, Maximum Watt's factor and Maastricht-Hannover nomogram) in allocating men to bladder contractility subgroups. Secondary aim was to explore whether preoperative contractility classification was associated with short-term flowmetry outcomes after BOP. MATERIALS AND METHODS: This multicenter retrospective cohort study included men who underwent BOP (2010-2016) for lower urinary tract symptoms with available baseline urodynamic study and 6-week postoperative flowmetry. Patients were classified according to BCI, Wmax and MH-nomogram into very weak (BCI < 50, Wmax < 5, MH-nomogram < 10th percentile), weak (BCI: 50-100, Wmax: 5-10, MH-nomogram 10-25th percentile) and normal detrusor contractility (BCI > 100, Wmax > 10, MH-nomogram > 25th percentile) subgroups. Concordance was quantified using percentage agreement and Cohen's linear weighted kappa (κ). Postoperative flowmetry outcomes were compared between subgroups within each classification and pre-postoperative differences were determined for each subgroup. RESULTS: One hundred and thirty three patients were included (median age 69 years). Agreement was highest between BCI and Wmax (78.9%, κ = 0.61, substantial), while agreement was weak between Wmax and MH-nomogram (48.9%, κ = 0.31) and negligible between BCI and MH-nomogram (37.6%, κ = 0.05). All subgroups showed improvement Qmax and PVR parameters after BOP, with no significant association found between preoperative contractility grade and postoperative outcomes. CONCLUSIONS: BCI, Wmax and the MH-nomogram show only limited concordance, particularly involving the MH-nomogram, and cannot be regarded as interchangeable. Contractility classification was not associated with postoperative outcomes, and all subgroups improved after BOP. These findings underscore the need for a clinically relevant urodynamic consensus definition of DU and support shared decision-making over classification-based patient selection alone.