Prostatic central zone volume, lower urinary tract symptom severity and peak urinary flow rates in community dwelling men

Purpose: Previous studies have suggested that central zone prostatic volume may be more strongly correlated with lower urinary tract symptom severity and peak urinary flow rates than total prostatic volume. We determine whether prostatic central zone volume and central zone index volume correlate better with these measures than total prostate volume in an age stratified, community based random sample of healthy white men. Materials and Methods: A cohort of 474 men were randomly selected from the 2,115 community dwelling men, 40 to 79 years old, who participated in the Olmsted County study of urinary symptoms and health status among men. All men had undergone transrectal ultrasound of the prostate. The total prostate and hypoechoic central zone volumes were caliper measured by 1 operator on static ultrasounds from baseline. Volumes were calculated with the prolate ellipsoid formula. The operator was blinded to clinical information and outcome. The associations between total prostate volume and central zone index (central zone volume/total volume), and American Urological Association (AUA) symptom index and peak urinary flow rates, respectively, were quantified with the Spearman rank correlation coefficient and least squares regression models. Results: There was a moderately strong correlation between patient age and central zone volume (r(s) 0.54, p <0.001), total prostate volume (r(s) 0.45, p <0.001) and central zone index (r(s) 0.38, p <0.001). The AUA symptom index and peak flow rates correlated less strongly with central zone volume (r(s) 0.17, p = 0.001 and r(s) -0.20, p <0.001, respectively) and total volume (r(s) 0.16, p <0.001 and r(s) -0.16, p <0.001, respectively). Central zone index weakly correlated with AUA symptom index (r(s) 0.08, p = 0.103) and peak urinary flow rate (r(s) -0.08, p = 0.0823). In regression models predicting AUA symptom index and peak now rates central zone volume added little information after accounting for age and total prostatic volume in predicting AUA symptom index (p = 0.55) and peak flow rate (p = 0.84). Conclusions: Central zone volume measured from static images optimized for total prostate volume no more closely correlated with lower urinary tract symptom severity or peak urinary flow rates than total prostate volume. Thus, the potentially greater imprecision in measuring central zone volume may not be offset by gains in strength of association with lower urinary tract symptom severity or peak urinary flow rates.