Standardized ultrasound method for assessing detrusor muscle thickness in children.

PURPOSE: We standardized transabdominal ultrasound measurement of bladder wall thickness in children and evaluated its reliability.

MATERIALS AND METHODS: Using ultrasonography we measured the thickness of the low echogenic layer of the ventral and dorsal bladder walls at increasing degrees of bladder fullness in the setting of voiding cystourethrography. For assessing intra-observer variability an observer blinded to the numerical values of the measurements studied 38 patients 0.2 to 13.7 years old (median age 1. 5). Measurements were performed as pairs of replicates at well-defined sites with reference to the urachal remnant, and rectal impression and/or contour. For assessing interobserver variability 3 independent observers measured the same child. Eight children 0.3 to 10.5 years old (median age 6.4) were evaluated at 2 degrees of bladder fullness per child.

RESULTS: The thickness of the low echogenic layer of the ventral and dorsal walls was 0.4 to 2.9 (median 0.9) and 0.4 to 2.8 mm. (median 1.1). The dorsal wall was slightly thicker than the ventral wall. The intra-observer and interobserver variability of measurements (standard deviation) was 0. 2 mm. for each wall part. There was a small systematic difference among observers.

CONCLUSIONS: It is possible to determine the thickness of the low echogenic layer of the bladder wall with a systematic and anatomically defined method of acceptably reliable measurements. The ventral and dorsal walls should continue to be measured until more is known about their pathological appearance.