Bladder shape has considerable impact on the accuracy of US estimation of bladder volume in children. Correction coefficients should be used for volume measurements of different bladder shapes.

The aim was to measure detrusor thickness in healthy children, using high frequency ultrasonography, to determine normal values that could be used for the evaluation of pathological bladder conditions. Ultrasound (US) was performed in 62 children (38 boys, 24 girls, 20 months - 18 years, mean 8.4+/-4.5 years) with the absence of clinical or laboratory pathological changes of the urinary tract. The detrusor thickness was measured at the posterior, anterior and lateral bladder walls, and the average thickness was calculated for each bladder wall in every child. The mean detrusor thickness was 1.17+/-0.45 mm (range 0.4-2.8 mm) for the anterior bladder wall, 1.25+/-0.45 mm (range 0.5-3.0 mm) for the posterior bladder wall, 1.18+/-0.44 mm (range 0.4-2.9 mm) for the left lateral wall, and 1.19+/-0.45 mm (range 0.4-2.8 mm) for the right lateral wall. There was a significant correlation of mean detrusor thickness with age. Using high-frequency US transducers it was possible to measure the detrusor thickness of the anterior and posterior bladder walls in all children. The mean normal detrusor thickness is 1.2+/-0.45 mm (range 0.4-3 mm) when the bladder is full. Future studies should evaluate this method in children with functional, neuropathic and anatomical dysfunctions of the lower urinary system.

Bladder weight in healthy children was determined ultrasonographically using a modified formula that takes into account the different shapes of the urinary bladder. Ultrasonographic examination of the bladder was performed on 92 healthy children (56 boys, 36 girls) with a 5-MHz transducer. Bladders were categorized into five groups according to shape, and three bladder diameters were measured. Ultrasound-estimated bladder weight (UEBW) was calculated according to the formula modified for bladder shape. Correction coefficients were used: 0.55 for round shape, 0.79 for ellipsoid, 0.92 for cuboid, 0.62 for triangular, and 0.78 for undefined shape. Twenty-three children had a round bladder (25%), 22 cuboid (24%), 21 ellipsoid (22.8%), 25 triangular (27.2%), and 1 child had an undefined bladder shape. Using linear regression analysis, a formula was derived for the calculation of normal values of the UEBW by age: UEBW (in grams) = A x 0.995 + 8.405 ( A=age in years). For simplicity in clinical use, the formula was modified to UEBW= A + 8.4. A statistically significant correlation was observed between UEBW and age ( r=0.78, p<0.05). UEBW correlates significantly with children's age. This simple formula is proposed for noninvasive calculation of normal UEBW by age that may be used for the objective and quantitative assessment of the degree of bladder wall hypertrophy. Further studies are needed to evaluate the potential of this method in the detection of pathological bladder conditions.

The aim of this study was to evaluate Doppler renal resistance index (RI) and RI ratio (RIR) in differentiating between obstructive and nonobstructive hydronephrosis in children and adolescents. The RI and RIR were measured in 32 healthy examinees (control group) and 29 patients with unilateral hydronephrosis. Ten patients had acute obstruction caused by a ureteric stone. Seven had obstructive hydronephrosis due to uretero-pelvic junction (UPJ) obstruction. Twelve patients had nonobstructive hydronephrosis. In controls the mean RI±S.D. was 0.615±0.04, and RIR 1.045±0.033. In children with acute obstruction RI was 0.692±0.035 and RIR 1.148±0.037. In UPJ obstruction RI was 0.631±0.054 and RIR 1.059±0.047. In nonobstructive dilatation RI was 0.61±0.038 and RIR 1.043±0.042. The RI and RIR differences were statistically significant between controls and patients with acute colic (p<0.01), and between patients with acute obstruction and with nonobstructive hydronephrosis (p<0.01). In detecting acute obstruction RI≥0.70 was found to have a 70% sensitivity and a 92% specificity. The RIR≥1.10 was found optimal to distinguish obstructive from nonobstructive dilatation (sensitivity 90%, specificity 83%). Both RI and RIR are significantly elevated in patients with acute obstruction. Renal Doppler seems to be useful in children and adolescents for the detection of acute renal obstruction, although it cannot differentiate chronic obstruction due to the UPJ obstruction and nonobstructive renal collecting system dilatation.

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