Ultrasound evaluation of kidney dimensions in neonates.

This study was done to measure normal renal dimensions of neonatal kidney at various gestational ages sonographically. Knowledge of these measurements may allow earlier diagnosis of a variety of abnormalities. Kidney dimensions (maximum longitudinal length, width, and anteroposterior diameter) were measured within 48 h after birth in 100 healthy neonates with gestational ages from 26.14 to 41.28 weeks and birth weights from 540 to 3250 g using a real time sector scanner with a 7.5 mHz transducer. Renal volume was calculated by volume (V) = L x W x T x 0.5233. Total body surface area (BSA) was determined by BSA = Wt0.425 x Lt0.725 x 71.84. Ponderal index was determined by PI = Wt (g) x 100/(Ht[cm])3. On linear regression analysis, a highly significant correlation was found between renal dimensions and body surface area, gestational age, body weight and length of the baby (p < 0.05). On step wise regression analysis, renal dimensions correlated only with body surface area and the gestational age of the neonate. Regression equations have been provided for rapid computation of renal length, width, and thickness in a given case based on body surface area and the gestational age. Mean (+/- 2 SD) renal volume and renal length were determined based separately on gestational age and body surface area. The data provided can be valuable for evaluating renal abnormalities in preterm neonates.