Tubular compensation for glomerular filtration rate decrease in chronic renal failure - the clinicopharmacologic point of view.

The decrease of GFR can be compensated for by the tubular functions of residual nephrons while the homeostasis of the internal milieu is maintained. A new method presented here enables us to estimate the adequacy of tubular compensation on the basis of investigations of fractional excretion (FE) of sodium, water, and potassium. If the extrarenal excretion of the determined substance is small in comparison with the intake (I), the adequate value of FE with respect to GFR and I can be calculated according to the following formula: FE = 1.15 I/GFR . S. In patients with GFR less than 0.17 ml/s, FENa reached the values of 20-25%, FEH2O: 30-35%, and FEK: 150-200%. The estimation of these parameters can help in indicating and controlling therapy by diuretics and dietary restrictions.