Noninvasive quantitative estimation of infravesical obstruction using ultrasonic measurement of bladder weight

Purpose: Ultrasound estimated bladder weight was compared to pressure-flow studies to test the ability of ultrasound estimated bladder weight to predict infravesical obstruction. Materials and Methods: A total of 65 men with urinary symptoms underwent ultrasonic measurement of bladder weight and pressure-flow studies. Assuming the bladder is a sphere, ultrasound estimated bladder weight was calculated from bladder wall thickness measured ultrasonically and intravesical volume. Results: Ultrasound estimated bladder weight correlated significantly (p < 0.0001) with the Abrams-Griffiths number, urethral resistance factor and the Schafer grade of obstruction. A cutoff value of 35 gm. for ultrasound estimated bladder weight revealed a diagnostic accuracy of 86.2% (56 of 65 cases) for infravesical obstruction with 12.1 (4 of 33) and 15.6% (5 of 32) false-positive and false-negative rates, respectively. Conclusions: Ultrasound estimated bladder weight can be measured noninvasively at the bedside and it is promising as a reliable predictor of infravesical obstruction.