OBJECTIVETo construct a function model that can be used in the diagnosis bladder outlet obstruction (BOO) resulting from benign prostatic hyperplasia, and to develop a diagram allowing the judgement of bladder outlet for patients with different detrusor contractility, especially with impaired one.

METHODSUrodynamic and clinical data of 131 men were analyzed retrospectively. By Logistic analysis, a function model was constructed. Based on the model, a diagram allowing the evaluation of bladder outlet was drawn. The cutoff point for diagnosing BOO with the function model and the curve was confirmed by ROC curve analysis.

RESULTSThe function model (BOOI) was obtained by the formula 5.03 x residual fraction + 0.04 x PdetatQmax - 0.20 x Qmax - 0.91 + alpha (alpha = 0 for those with low pressure-low flow on P-FS, alpha = 1.42 for high pressure-low flow, alpha = -7.30 for high pressure-high flow). The cutoff point for BOOI diagnosing BOO was 0.36. When validated, the sensitivity, specificity, positive predictive value, and negative predictive value were 85.7%, 91.7%, 96.0% and 73.3% respectively.

CONCLUSIONThe BOOI, with an easy calculation mode, could predict the probability of BOO. The sensitivity and specificity of the criterion for the diagnosis of BOO were satisfactory. The curve we drew could help to differentiate the obstructed men with low pressure-low flow and thus benefit them by surgical relief of their obstruction.