Effect on renal function of essential fatty acid supplementation in cystic fibrosis.

Changes in renal hemodynamics, sodium homeostasis, renal acidifying capacity, and aldosterone excretion were studied before and after long-term intravenous essential fatty acid supplementation for a period of 3 years in 11 patients with cystic fibrosis. The mean (+/- SD) glomerular filtration rate was high at the start of the study (133 +/- 18 ml/min/1.73 m2 body surface area) and decreased significantly (p less than 0.05) to within normal values after 1 year of essential fatty acid supplementation. The urinary elimination of an oral sodium load initially was very low (3.6 +/- 2.5 mmol/hr/1.73 m2 body surface area vs control subjects' values of 7.9 +/- 2.0; p less than 0.001) and increased during treatment but was not normalized (p less than 0.05 vs control subjects' values). Free water clearance and distal tubular sodium delivery, which were significantly decreased before treatment (p less than 0.01 and p less than 0.001 vs control subjects' values, respectively) did not increase significantly. The mean urinary aldosterone excretion did not significantly differ from that in control subjects before and after treatment. The acidifying capacity was disturbed, indicating a low renal bicarbonate threshold, and was changed during treatment in only 2 of 10 patients. These data indicate that essential fatty acid deficiency may contribute to the renal disturbances in cystic fibrosis.