Prognostic value of pressure-flow study in surgical treatment of benign prostatic obstruction

The prognostic value of pressure-flow study (P-FS) in the surgical treatment of bladder outlet obstruction (BOO) was retrospectively studied in patients with benign prostatic hyperplasia. In 74 patients who underwent surgical treatment for BOO, P-FS and free uroflowmetry were performed pre- and postoperatively. On P-FS, obstruction and detrusor contractility were analyzed according to the Schäfer nomogram. The patients were classified into the following 3 groups according to their preoperative P-FS: group A consisted of 39 patients with normal detrusors and obstruction (obstruction grade 3-6); group B consisted of 13 patients with weak detrusors and obstruction; and group C included 22 patients with weak or very weak detrusors combined with minimal obstruction, if any (obstruction grade 0-2). Postoperatively, the detrusor pressure at maximal flow rate and obstruction grades on P-FS improved significantly in groups A and B but not in group C. The rate of improvement was most prominent in group A, followed by groups B and C. On free uroflowmetry, however, a significant improvement occurred in all three groups with respect to maximal flow rate, average flow rate, and postvoid residue. Moreover, the rate did not differ among the three groups except for the maximal flow rate as determined between groups A and C. Although good detrusor contractility and evident obstruction on analysis of P-FS will guarantee the best surgical outcome, subjects with weak detrusors and minimal obstruction will also have a good outcome by the relief of BOO. In the weak detrusor, P-FS may be limited in diagnosing obstruction and have a low prognostic value, and such patients should not necessarily be excluded from surgical indications.