Pressure-flow studies in patients with benign prostatic hyperplasia: a study comparing suprapubic and transurethral methods.

AIM To compare the use of the suprapubic puncture method versus the transurethral method in pressure-flow studies in patients with benign prostatic hyperplasia. METHODS Twenty-three men with benign prostatic hyperplasia underwent both suprapubic and transurethral pressure-flow studies during a single session. Standard pressure-flow variables were recorded in all patients with both methods, enabling calculation of obstruction using commonly used grading systems, such as the urethral resistance algorithm, the Abrams-Griffith (AG) number and the Schaer linear nomogram. RESULTS There were statistically significant differences between the methods in the mean values of maximum flow rate (P < 0.05), detrusor pressure at the maximum flow (P < 0.01), urethral resistance algorithm (P < 0.01), AG number (P < 0.01) and maximum cystic capacity (P < 0.01). Of the men in the study, 10 (43.5%) remained in the same Schaer class with both methods and 18 (78.3%) in the same AG number area. Using the transurethral method, 12 (52.2%) men increased their Schaer class by one and 1 (4.3%) by two. There were also differences between the suprapubic and transurethral methods using the AG number: 4 (17.4%) men moved from a classification of equivocal to obstructed and 1 (4.3%) from unobstructed to equivocal. CONCLUSION The differences between the techniques for measuring intravesical pressure alter the grading of obstruction determined by several of the commonly used classifications. An 8 F transurethral catheter significantly increases the likelihood of a diagnosis of bladder outlet obstruction when compared with the suprapubic method.