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 flow rate (p(det)Q(max)), voided volume, and residual urine were studied. Also the agreement in interpretation of pressure-flow tracings between investigators and a single blinded central reader acting as a quality control center (QCC) were assessed. In addition, correlations between p(det)Q(max) and patient age, International Prostate Symptom Score (IPSS), free maximum flow rate (Q(max)), and prostate volume were calculated. Using suprapubic pressure recording, 216 men with lower urinary tract symptoms (LUTS) due to benign prostatic enlargement (BPE) were investigated in 11 centers. In each pressure-flow study, three sequential voids were performed, and quality controlled recordings were analyzed for Q(max)PQ and p(det)Q(max) by the QCC. Transrectal ultrasound was used to measure the prostate volume. Mean Q(max)pQ did not change, but p(det)Q(max) decreased significantly in the second and third sequential voids. Using the Abrams-Griffiths nomogram definition of obstruction, 125 patients (67%) were classified as obstructed from the first void, but only 111 patients (59%) from the third void. The agreement between 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(max) and prostate volume. In summary, there was no significant change in Q(max)PQ, but P(det)Q(max) decreased for the three consecutive voids, which can be explained by a decrease in outlet resistance. The agreement between the investigator ansi QCC interpretations shows the value of a standardized technique, supporting the feasibility of multicenter urodynamic studies, There is a modest, but statistically significant, correlation between detrusor pressure and prostate size, supporting the hypothesis that prostate size is a contributing factor in symptomatic BPH. Neurourol. Urodynam. 18:17-24, 1999. (C) 1999 Wiley-Liss, Inc.