Bladder outlet obstruction in men with acute urinary retention: an urodynamic study.

Objective: To identify clinical predictors of bladder outlet obstruction (BOO) in men with the first episode of spontaneous acute urinary retention (AUR), in order to facilitate patient selection for early de-obstructive prostate surgery.

Methods: A multichannel urodynamic investigation was performed in 156 consecutive men ≥ 50 years five days following AUR. Clinical routine parameters were evaluated for their ability to predict BOO, which was defined as a BOO-index (BOOI) >40. Univariable and multivariable logistic regression models were fitted. A nomogram was constructed from significant variables of a reduced multivariable model. Discrimination and calibration of the nomogram were assessed.

Results: The mean age of the 156 men was 71.6 years, and the mean drained volume was 953 mL. Seventy-two men (46.2 %) had severe AUR-associated pain. On urodynamic evaluation, 79 (50.6 %) were obstructed (BOOI > 40). In multivariable regression analysis, age (p = 0.014) drained volume (p = 0.044) and pain intensity (p < 0.001) were independently associated with BOO. These variables formed the basis of the nomogram, which predicted BOO with a bootstrap-corrected accuracy of 78.2 %. The positive predictive value, sensitivity, and specificity of a 70 % nomogram cutoff was 83, 51, and 90 %, respectively. Decision-curve analysis demonstrated a net benefit with use of the nomogram.

Conclusions: The routine clinical parameters age, drained volume, and pain intensity are independent predictors of BOO in men with AUR. According to our model, patients with a nomogram predicted BOO probability of >70 % might be candidates for early surgery. External validation of the nomogram is advocated.