Urodynamics in prostatism. II. Prognostic value of pressure-flow study combined with stop-flow test

In a prospective study the prognostic value of preoperative pressure-flow studies in prostatism was examined. The indications for prostatectomy were based on non-urodynamic data only. An extensive urodynamic evaluation was performed pre- and postoperatively, including uroflowmetry, water cystometry and pressure-flow study combined with stop-flow test. In total the data from 130 patients were considered. The material was classified with respect to the "urethral resistance relation" (URR) and the "bladder output relation" (BOR). According to the first criterion 87 patients were obstructed, 36 unobstructed, while 7 were unclassifiable and finally excluded. In most urodynamic variables, the two groups differed preoperatively, but no differences were revealed postoperatively. However, the obstructed group did considerably better postoperatively as to the symptomatic outcome. The success rate was 93% as opposed to 78% in the unobstructed patients (p less than 0.02). For the BOR classification, the theoretical maximum flow rate (Qm,est) was employed forming two groups: 57 patients with decreased bladder speed (Qm,est less than 35 ml/sec) and 41 patients with normal speed (Qm,est greater than or equal to 35 ml/sec). Few differences in urodynamic variables were found both pre- and postoperatively, but no significant difference was shown in success rates. In conclusion the URR proved a significant prognostic value in prostatism and is recommended in the preoperative work-up, especially in patients with equivocal uroflow studies. No convincing prognostic role could be attributed to the BOR.