Repeated pressure-flow studies in the evaluation of bladder outlet obstruction due to benign prostatic enlargement

Test-retest reliability of repeated voids in pressure-flow studies and the influence on maximum flow rate (Q(max)pQ), detrusor pressure at maximum flo w rate (p(det)Q(max)), voided volume, and residual urine were studied. Also the agreement in interpretation of pressure-flow tracings between investig ators and a single blinded central reader acting as a quality control cente r (QCC) were assessed. In addition, correlations between p(det)Q(max) and p atient age, International Prostate Symptom Score (IPSS), free maximum flow rate (Q(max)), and prostate volume were calculated. Using suprapubic pressu re recording, 216 men with lower urinary tract symptoms (LUTS) due to benig n prostatic enlargement (BPE) were investigated in 11 centers. In each pres sure-flow study, three sequential voids were performed, and quality control led recordings were analyzed for Q(max)PQ and p(det)Q(max) by the QCC. Tran srectal ultrasound was used to measure the prostate volume. Mean Q(max)pQ d id not change, but p(det)Q(max) decreased significantly in the second and t hird sequential voids. Using the Abrams-Griffiths nomogram definition of ob struction, 125 patients (67%) were classified as obstructed from the first void, but only 111 patients (59%) from the third void. The agreement betwee n the investigator assessment and that of a single blinded reader was good. There was no significant correlation between p(det)Q(max) and patient age, IPSS, and Q(max), whereas a modest correlation was found between p(det)Q(m ax) and prostate volume. In summary, there was no significant change in Q(m ax)PQ, but P(det)Q(max) decreased for the three consecutive voids, which ca n be explained by a decrease in outlet resistance. The agreement between th e investigator ansi QCC interpretations shows the value of a standardized t echnique, supporting the feasibility of multicenter urodynamic studies, The re is a modest, but statistically significant, correlation between detrusor pressure and prostate size, supporting the hypothesis that prostate size i s a contributing factor in symptomatic BPH. Neurourol. Urodynam. 18:17-24, 1999. (C) 1999 Wiley-Liss, Inc.