[Understanding renal functional reserve].

Renal function is usually estimated through the blood measurement of creatinine, which allows estimating the glomerular filtration rate (GFR). However, this value only decreases when half the nephrons are damaged, limiting the detection of early renal disease. The ingestion of an important amount of protein can increase the GFR. The renal functional reserve concept is the difference between the maximal GFR, stimulated by an important protein intake, and the baseline GFR. A diminished renal functional reserve could mean glomerular hyperfiltration and early renal disease. This value could help predicting patients more likely to present with acute renal injury and evaluating the capacity of the kidney to increase their function before a nephrectomy.