Effect of gender and lean body mass on kidney size in healthy 10-year-old children

When evaluating renal abnormalities. kidney volume is an important paramete r. Most reference materials on kidney size in children are based on data fr om pediatric patients examined for non-uronephrological problems. Renal siz e is traditionally related to body height. weight, or surface area, but not to body composition. As part of a prospective cohort study we have examine d 102 healthy 10-year-old children measuring kidney volume by ultrasonograp hy. body composition by dual energy X-ray absorptiometry, and body height a nd weight. Boys had significantly larger kidneys than girls. The strongest predictor of kidney volume was lean body mass, overruling height, weight, a nd surface area. When total kidney volume was related to lean body mass as a ratio, the gender difference in kidney size was no longer significant. A strong negative correlation was found between fat body mass and kidney volu me. In conclusion, the strongest predictor of kidney volume in healthy 10-y ear-old children is lean body mass. The correlation is likely to reflect an association between metabolic active tissue, renal solute load, and kidney volume. We have currently no explanation for the negative correlation betw een fat body mass and kidney volume.