[Urodynamic evaluation of alpha-1 blocker tamsulosin on benign prostatic hyperplasia using pressure-flow study]

In order to evaluate the precise effect of alpha-1 blocker on benign prostatic hyperplasia, symptomatic and urodynamic parameters were compared between before and after 4 week administration of tamsulosin hydrochloride (0.2 mg/day) on 18 patients with untreated benign prostatic hyperplasia.

Symptoms were scored with international prostate symptom score (I-PSS) and urodynamic parameters were measured with pressure-flow study.

The total score of I-PSS decreased significantly although the peak urinary flow rates, average flow rates or post-void residuals did not show a significant improvement after the treatment. On the other hand, the statistical analysis of pressure-flow studies revealed a significant decrease of vesical pressure at opening, at peak flow and at end of voiding after the treatment. In one patient, in whom the voided volume and urinary flow rate kept the same level throughout the treatment course, the total energy expelled from the bladder was calculated with the formula given as W = integral (pQ)dt. Both the detrusor work and vesical work (sum of detrusor contraction and abdominal straining) showed a marked decrease after the treatment.

It is suggested that alpha-1 blocker relieves overload of the detrusor and improves symptoms by reducing the energy demands for bladder emptying, even in case the flow rate does not improve. The urodynamic procedure including pressure flow study is a useful means for not only diagnosing bladder outflow obstruction but also assessing overload or impaired contractility of the detrusor.