Glomerular and Tubular Kidney Stress Test: New Tools for a Deeper Evaluation of Kidney Function.

Kidney function has been traditionally identified with glomerular filtration rate (GFR). However, the kidney has multiple functions beyond filtration and a careful evaluation of its whole spectrum of activities should be carried out. Furthermore, the kidney presents a functional reserve capacity both at glomerular and tubular level. In presence of appropriate stimuli, patients with intact nephron mass can increase their GFR and tubular secretion. The difference between maximal capacity and baseline function represents the renal functional reserve (RFR). Glomerular and tubular kidney stress test may help to evaluate RFR and improve the clinicians' ability to better diagnose and prognosticate both acute and chronic kidney disease.