[Clinical application of the radiolabeled bile salt tolerance test]

The labeled bile salt tolerance test is the measure of the decrease in plasmatic radioactivity after intravenous injection of carboxyl-14C-labeled chenic acid. The label is distributed in the blood, taken up by hepatocytes and then secreted in the bile. The decrease in plasmatic radioactivity during the 4 h following the injection follows a bi-exponential curve. It has been studied in 6 normal subjects, 4 patients equipped with "T tube", 3 cases of acute viral hepatitis, 4 cases of hepatic steatosis, and 6 cases of hepatic cirrhosis. The first slope (b1) represents the hepatic uptake of the label. It is lowered in cases of viral hepatitis and in cirrhosis. The second slope (b2) represents hepato-biliary secretion of the label. It is lowered in patients equipped with a "T tube". From 100 min after the injection, the plasma concentration of radioactivity remains constant. This is the residual value (R), and it is very low in normal subjects. It is increased in cases of acute viral hepatitis and cirrhosis, indicating displacement of a fraction of the bile salt pool into peripheral blood. After a standard meal, the R value is not modified in the normal subject. In cases of steatosis and cirrhosis, a temporary peak may be seen, indicating recirculation of the label towards the periphery due to a porto-systemic shunt or a hepatocyte lesion.