Analysis of the Pressure-Flow Study in Weak Detrusor Patients with Benign Prostatic Hypertrophy

Pressure-flow study is a method used to evaluate the degree of bladder outlet obstruction and the strength of detrusor contractility during voiding. However, whether or not the operation for benign prostate hyperplasia should be avoided in detrusor underactivity patients remains controversial. To address this, we performed a retrospective analysis of our pressure-flow study data for benign prostate hyperplasia patients. We especially focused on the backgrounds of patients with weak detrusor contractility.

Patients (n = 288; average age, 71.5 years) who underwent pressure-flow study to evaluate operative indications between February 2001 and April 2010 were included in this study. We analyzed the relationships between background factors and detrusor contraction strength according to Schäfer's nomogram.

Patients with weak detrusor contractility had poor flow (5.81 mL/sec) and low voided volume (141.2 mL) compared to patients with normal (8.77 mL/sec, 202.0 mL) or strong (8.97 mL/sec, 178.3 mL) detrusor contractility. Twenty-six of 74 weak detrusor patients underwent prostate operation. The operated group had high obstruction grade (3.35, P < 0.001), but a low rate of detrusor overactivity (19.2%, P < 0.05), compared to the non-operated group (2.16, 41.7%). The operated group also had high urinary retention rate (38.5%) compared to the non-operation group (18.8%).

We performed prostate surgery in patients who had episodes of urinary retention, with outlet obstruction, and with no detrusor overactivity, even in those with weak detrusor contractility. The operation may not be contraindicated for these patients. Pressure-flow study is an important tool to ensure adequate informed consent.