Navigating Intermediate Bladder Outflow Obstruction: A Combined DCI–BOOI Framework Incorporating BWT for Predicting Surgical Outcomes in Men With Lower Urinary Tract Symptoms

BACKGROUND: The 2023 ICS-SUFU pressure-flow standard recommends the ICS Bladder Outflow Obstruction Index (BOOI) and ICS Detrusor Contraction Index (DCI) as continuous parameters for grading bladder outflow obstruction (BOO) and detrusor voiding contraction (DVC) in men. Patients with intermediate BOO (BOOI 20-40) may nevertheless represent a heterogeneous population, making it difficult to determine whether transurethral resection of the prostate (TURP) is likely to provide clinical benefit. OBJECTIVE: To explore whether detrusor overactivity (DO) and ultrasound-estimated bladder wall thickness (BWT) are associated with postoperative outcomes among men with intermediate BOO undergoing TURP. METHODS: This single-center retrospective cohort study included 234 men who underwent TURP after preoperative urodynamic testing and sonographic evaluation between January 2021 and June 2024. Pressure-flow findings were classified using ICS-BOOI and ICS-DCI, with particular attention to intermediate BOO (BOOI 20-40). The primary outcome was surgical success, defined as a ≥ 50% reduction in International Prostate Symptom Score (IPSS) at 6 months. Multivariable logistic regression and receiver operating characteristic curve analyses were performed to assess the exploratory value of BOOI, DO, and BWT. RESULTS: The overall surgical success rate differed across pressure-flow phenotypes. Patients with BOO and normal DVC had a higher success rate than those with weak DVC. Among 85 patients with intermediate BOO, the overall success rate was 47.1%, with marked heterogeneity across DO-BWT subgroups. Intermediate-BOO patients with both DO and BWT > 2.5 mm had a substantially higher success rate than those without DO and with BWT ≤ 2.5 mm. The full model incorporating BOOI, DO, and BWT had an area under the curve of 0.799, compared with 0.528 for BOOI alone; however, subgroup sparsity and complete overlap of increased BWT with DO in the intermediate group limit interpretation of their independent contributions. CONCLUSIONS: Men with intermediate BOO were heterogeneous in this retrospective cohort. Increased BWT was associated with a higher surgical success rate, but no patient in the intermediate group had increased BWT without DO; therefore, the independent contribution of DO could not be determined. BWT may provide adjunctive screening information, whereas the role of DO remains exploratory and requires prospective validation.