Age related urodynamic changes in patients with benign prostatic hyperplasia

We determined age related urodynamic changes in patients with untreated symptomatic benign prostatic hyperplasia (BPH).

A total of 222 patients (mean age 67.3 years, range 45 to 90) with the clinical diagnosis of symptomatic BPH was entered into a prospective protocol evaluating the international prostate symptom score (I-PSS), prostate volume, noninvasive uroflowmetry, residual volume and a pressure-flow study. To obtain a homogeneous study population only patients with a noninvasive maximum flow rate of 15 ml. per second or less and an I-PSS of 7 or more were eligible.

There was no correlation between age and I-PSS (p > 0.05) but there was a statistically significant decrease in maximum flow rate (p = 0.045) and voided volume (p = 0.0013) with age. Prostate volume increased constantly from 31.3 to 64.4 ml. in patients 45 to 50 and older than 80 years, respectively (p < 0.0001). Pressure-flow studies revealed an age related decrease in cystometric bladder capacity (p = 0.0003) and invasive maximum flow rate (p = 0.0057) but no changes in detrusor pressure at maximum flow rate (p > 0.05), maximum detrusor pressure (p > 0.05) and linear passive urethral resistance relation (p > 0.05). The incidence of urodynamically proved bladder instability increased from 20 to 47% in men 45 to 50 and older than 80 years, respectively.

The well established age related decrease in maximum flow rate and voided volume in patients with prostatism cannot be attributed to an increase in bladder outflow obstruction or impaired detrusor function. Because 60% of all men older than 80 years did not have urodynamic obstruction despite a decreased maximum flow rate of 10 to 15 ml. per second, all patients meeting these criteria and having symptoms bothersome enough to justify surgery should undergo pressure-flow studies before surgical intervention.