Noninvasive evaluation of bladder compliance in children using ultrasound estimated bladder weight.

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.