Sonographic assessment of renal size and growth in premature infants

Low birth-weight infants are at risk for renal disease when renal insults occur in the neonatal period. Renal growth as measured by sonography over time is utilized by many nephrologists as predictors of future renal disease.

To identify infants at risk by defining normal renal growth for the very premature infant.

Renal growth was evaluated in 30 infants whose birth weight was 1,500 g or less and gestational age was <31 weeks. During a 2-month time period, three US measurements were taken (first week of life, age 28 days, and age 56 days or earlier if discharged). Infants were divided according to birth weight: the extremely low birth-weight group (ELBW) was <1,000 g (n = 14), and the very low birth-weight group (VLBW) was 1,000-1,500 g (n = 16).

In both groups, the right and left renal lengths were similar. In the ELBW group, the initial mean length was 3.25 cm and grew to 4.16 cm, while the mean volume was 4.85 cm and grew to 10.39 cm. In the VLBW group the initial mean length was 3.69 cm and grew to 4.35 cm while the mean volume was 7.25 cm and grew to 11.83 cm.

These data establish normal expected growth for future studies.