The Diagnostic Efficacy of 3-Dimensional Ultrasound Estimated Bladder Weight Corrected for Body Surface Area as an Alternative Nonurodynamic Parameter of Bladder Outlet Obstruction

Abstract

We investigated the relationship between ultrasound estimated bladder weight/corrected ultrasound estimated bladder weight and the bladder outlet obstruction index derived from pressure flow study to evaluate its diagnostic efficacy to predict bladder outlet obstruction. A total 193 men older than 50 years with lower urinary tract symptoms were enrolled in this study. Ultrasound estimated bladder weight measurements were made with a 3-dimensional ultrasound system. Corrected bladder weight was defined as ultrasound estimated bladder weight divided by body surface area on data analysis. The study population was classified into obstructed and unobstructed groups (bladder outlet obstruction index 40 or greater and less than 40, respectively). We evaluated the correlation between bladder outlet obstruction and clinical parameters, including bladder weight/corrected bladder weight and the diagnostic accuracy of bladder weight/corrected bladder weight for bladder outlet obstruction. A total of 50 (26%) and 143 patients (74%) were categorized as obstructed and nonobstructed, respectively. Corrected bladder weight, maximum urine flow and the bladder contraction index showed statistically significant differences between the groups. Bladder weight/corrected bladder weight positively correlated with the bladder outlet obstruction index and corrected bladder weight showed a stronger correlation. Corrected bladder weight was significantly increased depending on obstruction severity. When corrected bladder weight was used to diagnose obstruction, sensitivity, specificity, and positive and negative predictive values were 61.9%, 59.8%, 33.8% and 82.6%, respectively, at a 28 gm/m(2) cutoff. Ultrasound estimated bladder weight/corrected ultrasound estimated bladder weight is a statistically significant parameter correlating with bladder outlet obstruction. However, bladder weight/corrected bladder weight alone was insufficient to predict bladder outlet obstruction due to its weak correlation with and low accuracy for diagnosing obstruction.