Effects of amiloride on renal lithium handling in nonazotemic ascitic cirrhotic patients with avid sodium retention.

The reliability of lithium clearance as an index of distal fluid delivery in cirrhosis with ascites and in other clinical conditions characterized by low fractional sodium excretion has not yet been proven. In particular, lithium reabsorption in the amiloride-sensitive segment of the distal tubule, as evidenced in experimental studies, has not been excluded in such clinical conditions. Thus the acute effect of amiloride on renal lithium handling in 15 nonazotemic ascitic cirrhotic patients with avid sodium retention was evaluated after at least 5 days of controlled sodium intake. Renal plasma flow, glomerular filtration rate, fractional sodium excretion, fractional lithium excretion, fractional potassium excretion, fractional excretion of uric acid, plasma renin activity, plasma aldosterone and human atrial natriuretic peptide were evaluated before and for 6 hr after the administration of amiloride (20 mg/os). After amiloride administration a volume replacement scheme was enacted with intravenous amounts of saline solution, determined by the diuretic and natriuretic effect of the drug, to avoid volume depletion. Amiloride induced a prompt and sustained increase in fractional sodium excretion (from 0.28% +/- 0.09% to 1.0% +/- 0.41%, p less than 0.001) and a decrease in fractional potassium excretion (from 9.38% +/- 5.98% to 3.28% +/- 2.24%, p less than 0.0025), whereas it did not affect fractional lithium excretion and fractional excretion of uric acid. No change was observed in renal plasma flow, glomerular filtration rate, plasma renin activity, plasma aldosterone and human atrial natriuretic peptide. It was concluded that lithium is not reabsorbed in the amiloride-sensitive segment of the distal tubule in nonazotemic ascitic cirrhotic patients with avid sodium retention.