Oral ammonia tolerance test in patients with portal hypertension.

Eighty patients with portal hypertension due to various hepatic diseases were subjected to the oral ammonia tolerance test (OATT). Blood samples were collected before and at 30-min intervals after the administration of ammonium chloride (50 mg/kg). The ammonia levels, and the OATT curve patterns and sigma NH3-N values were determined and it was investigated whether there are correlations between these values and various other parameters of hepatic function. The results of OATT correlated with the plasma disappearance rate of indocyanine green and the molar ratio of branched chain amino acids to aromatic amino acids. Our findings suggest that the OATT may reflect the degree of hepatic parenchymal disorders rather than the hepatic circulatory abnormalities and that they may represent a valuable aid in the differential diagnosis of hepatic diseases and in determining the operative indication.