Distribution of post-void residual urine volume in randomly selected men

Purpose: We describe the distribution of post-void residual urine volume and its relationship to other urological measurements in a random sample of men. Materials and Methods: Post-void residual was measured by transabdominal ultrasonography after voiding and prostate volume was measured by transrectal ultrasonography in 477 randomly selected community dwelling white men as part of a baseline urological evaluation. Symptoms were characterized with the American Urological Association symptom index. Acute urinary retention cases with catheterization in the subsequent 3 to 4 years were identified through chart review. Results: The distribution of post-void residual was highly skewed with a median of 9.5 ml., and 25th and 75th percentiles equal to 2.5 and 35.4, respectively. There was a significant correlation of post-void residual with prostate volume (r, = 0.24, p <0.001). The odds of post-void residual greater than 50 ml. were 2.5 times greater for men with prostate volume greater than 30 ml. than those with smaller prostates. In regression analyses post-void residual did not appear to be associated with the American Urological Association symptom index, age or peak urinary flow rate. Men with enlarged prostate volume or post-void residual greater than 50 ml. at baseline were about 3 times as likely to have subsequent acute urinary retention with catheterization during 3 to 4 years of followup. Conclusions: These results suggest little variation in the distribution of post-void residual urine volume across age groups or levels of urinary symptoms and peak urinary flow rate. However, a somewhat stronger relationship was found between residual urine and prostate volume. Measurement of the volume of residual urine in the bladder after voiding is a common procedure in urological examination of patients presenting with lower urinary tract symptoms, and has traditionally been thought to have a prominent role in identifying those with obstruction. The Agency for Health Care Policy and Research guidelines for diagnosis and treatment of benign prostatic hyperplasia (BPH) listed the measurement of post-void residual urine volume as an optional procedure' but the 1995 international consultation on BPH procedures recommended its use.2 Despite the controversy surrounding the usefulness of post-void residual as a diagnostic test, it continues to be used. In a study that compared transurethral resection of the prostate with watchful waiting for moderate symptoms of BPH" treatment failure was defined as the presence of a high volume of residual urine (greater than 350 mI.1. Of 40 urological units in Norway 92.5% routinely use post-void residual measurement as a diagnostic test,J and most suggest that high values of post-void residual are a n indication for surgery. Numerous previous studies have reported on the high degree of variation associated with this measure.l.5-9 Measure