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 wheth er prostatic central zone volume and central zone index volume correlate be tter with these measures than total prostate volume in an age stratified, c ommunity 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 O lmsted County study of urinary symptoms and health status among men. All me n 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 out come. The associations between total prostate volume and central zone index (central zone volume/total volume), and American Urological Association (A UA) symptom index and peak urinary flow rates, respectively, were quantifie d with the Spearman rank correlation coefficient and least squares regressi on 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 i ndex 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 vol ume (r(s) 0.16, p <0.001 and r(s) -0.16, p <0.001, respectively). Central z one index weakly correlated with AUA symptom index (r(s) 0.08, p = 0.103) a nd peak urinary flow rate (r(s) -0.08, p = 0.0823). In regression models pr edicting AUA symptom index and peak now rates central zone volume added lit tle information after accounting for age and total prostatic volume in pred icting 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 s ymptom 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.