Effect of catheter size on urodynamic assessment of bladder outlet obstruction

Abstract

Objectives To examine the effect of cross-sectional catheter diameter on urodynamic measurement of bladder outlet obstruction as predicted by the Abrams-Griffiths nomogram. Methods Thirty-one patients with symptomatic benign prostatic hyperplasia underwent free flow measurements followed by pressure-flow urodynamic evaluation using 5F and 10F urethral catheters in randomly assigned order. The measurements of voided volume, maximal flow rate (Qmax), postvoid residual volume, and detrusor pressure at maximal flow (PdetQmax) were compared. Data points were then plotted on the Abrams-Griffiths nomogram, and categorization of bladder outlet obstruction was assigned for each catheter size. Results The use of 10F catheters resulted in both a significant decrease in Qmax and increase in PdetQmax compared with the use of 5F catheters. Of 31 patients, 10 (32%) were incorrectly categorized as obstructed according to the Abrams-Griffiths nomogram when the larger sized catheter was used, and 17 (55%) experienced migration from a less obstructed to a more obstructed category. Conclusions The use of 5F catheters allows for more accurate diagnosis of bladder outlet obstruction. In urodynamic evaluations, the larger size 10F catheters should be avoided, especially in patients with borderline symptoms.