Purpose: In healthy children as well as those with urinary disturbance we determined ultrasound estimated bladder weight with the aim of revealing its possible usefulness as a measure of bladder compliance.
Materials and methods: We measured ultrasound estimated bladder weight in 71 healthy children with a mean age of 10.3 years, and determined a standard value. A total of 82 patients with a mean age of 9.6 years with urinary disturbance also underwent ultrasound estimated bladder weight measurement as well as conventional urological examinations, including filling cystometry.
Results: In healthy children ultrasound estimated bladder weight increased with age, showing a significant linear correlation (r = 0.80, p < 0.0001). Using the formula for linear correlation, 0.86 x patient age + 6.9 gm., we obtained an age matched estimated weight. In 82 patients the percent deviation of the estimate from age matched values was calculated using the formula, (measured ultrasound estimated bladder weight -age matched ultrasound estimated bladder weight)/age matched ultrasound estimated bladder weight x 100, and then correlated with bladder compliance. In 75 of 77 patients (97%) with compliance of 10 ml./cm. water or more the estimate was within 100% deviation. In contrast, 4 of 5 patients (80%) with a low compliant bladder (less than 10 ml./cm. water) had an ultrasound estimated bladder weight greater than 100% deviation. When the estimate was within 100% deviation, all but 1 patient (75 of 76, 98.7%) had compliance of 10 ml./cm. water or more compared to 33.3% (2 of 6) of those with an estimate greater than 100% deviation. As a result, with the use of a cutoff value of 100% deviation ultrasound estimated bladder weight predicted a low compliant bladder with a diagnostic accuracy as high as 96.3% (79 of 82 cases).
Conclusions: Ultrasound estimated bladder weight may be used to evaluate bladder compliance in children. It seems to be a suitable noninvasive urodynamic test in children with suspected urodynamic abnormalities.