Measurement of renal functional reserve in children.

Renal functional reserve was measured during 89 studies in 78 children as the difference between the baseline glomerular filtration rate (GFR) and that following a protein meal. GFR was measured using creatinine as the filtration marker in children pre-treated with cimetidine. The children had been on a diet free of meat, fish, and fowl for 24 h. The protein meal to stimulate GFR was derived from milk, cheese, eggs, and baked goods. The increase in GFR following the protein meal was due mainly to an increase in the glomerular filtration of creatinine, with a small contribution by decreased serum creatinine concentration. This study confirmed that renal functional reserve can be measured using a meat-free protein meal to stimulate GFR. The protocol employed is a relatively noninvasive and inexpensive procedure for identifying glomerular hyperfiltration in children.