Ammonia tolerance in liver disease.

Abstract

Abstract Normal ammonia tolerance was observed in patients with, obstructive jaundice, fibrosis and/or fatty infiltration of the liver and in most patients with acute hepatitis. In several of the patients with hepatitis in whom abnormal ammonia tolerance was found, esophageal varices, which may have accounted for the impaired ammonia tolerance, were demonstrated. Ammonia tolerance was abnormal in 83 per cent of 60 patients with cirrhosis. Impaired ammonia tolerance in cirrhosis appeared to be related more closely to the degree of development of portal collateral circulation than to hepatic functional damage. In patients with portacaval shunts ammonia tolerance was much more abnormal than in the cirrhotic group, despite less severely deranged liver function. Abnormal ammonia tolerance appears to be primarily a gross index of the amount of portasystemic anastomoses. Severe hepatic parenchymal damage may also impair ammonia clearance, although to a lesser degree. Simultaneous measurements of arterial and venous ammonia levels disclosed that although ammonia tolerance tests performed on venous blood are usually valid, increased arteriovenous uptake of ammonia may occasionally result in false negative tests. Arterial ammonia levels are consequently of greater diagnostic value. The ammonia tolerance test is a simple, safe, and reliable screening test for the estimation of the presence of portasystemic collateral circulation.