Ultrasonic measurement of bladder weight as a novel urodynamic modality

Although pressure-flow studies (PFS) are currently recognized as the gold standard for the diagnosis of infravesical obstruction, their clinical use is limited, due to the invasive nature of procedure. Recently, we developed a new urodynamic parameter, ultrasound estimated bladder weight (UEBW), which was calculated from the bladder wall thickness measured ultrasonically and intravesical volume. Our comparative study between UEBW and PFS showed that UEBW diagnosed infravesical obstruction with a diagnosis accuracy of 73% using a cut-off value of 35 gm. UEBW could also be used as a reliable tool in monitoring therapeutic effects on BPH patients in terms of the relief of obstruction. In addition, UEBW is of clinical use in the management of neurogenic bladder dysfunction, in which there was a significant negative correlation noted between UEBW and bladder compliance. Consequently, UEBW could be a reliable predictor for a low-compliant bladder. Since UEBW can be obtained non-invasively, it is readily applicable to pediatric urology. In healthy children, UEBW increased significantly with age. For the evaluation of UEBW in an individual child patient, the deviation from age-matched UEBW, obtained from the formula of the linear correlation between UEBW and age, was employed. In our recent studies, the deviation from age-matched UEBW is likely to be used as a predictor for bladder dysfunction in children, such as secondary vesicoureteral reflux and a low-compliant bladder. In conclusion, UEBW is promising as a non-invasive urodynamic modality capable of evaluating bladder hypertrophy with its functional abnormalities.