Urodynamics in prostatism. I. Prognostic value of uroflowmetry.

A prospective study was undertaken to examine the prognostic value for the symptomatic outcome of prostatic surgery of preoperative urodynamic testing in patients with prostatism. The study design included selection of patients for prostatic surgery by means of classic non-urodynamic urologic investigations such as history, residual urine, serum creatinine, cystoscopy and possibly intravenous urography. In addition an extensive urodynamic work-up (uroflowmetry, cystometry and pressure-flow study with stop-test) was included. The results of the urodynamic studies were unknown to the surgeon selecting the patients for operation. This evaluation was repeated 6 months postoperatively. Totally 139 patients entered the study. The patients were classified according to the preoperative maximum flow rate (Qmax) and in spite of preoperative differences in uroflow, pressure-flow variables and symptom scores, no differences of clinical significance were noted postoperatively among the groups. However, the high-flow group (preoperative Qmax greater than or equal to 15 ml/sec) had a statistically significant lower success rate as judged by the patients subjective evaluation of the outcome of surgery. An analysis of diagnostic sensitivity and specificity indicated Qmax = 15 ml/sec as a relevant cut-off value regarding preoperative identification of patients at risk of a less favourable outcome of surgery. This group of patients was characterized by a higher incidence of persistent uninhibited detrusor contractions at follow-up and a lower incidence of preoperative infravesical obstruction. In conclusion we recommend uroflowmetry in the preoperative evaluation of patients with prostatism.