RESUMEN
In a group of 29 patients with mechanical icterus and a control group of 38 patients (acute, chronic hepatitis and hyperbilirubinemia) there have been followed up alkaline phosphatase, leucinaminopeptidase and gammaglutamil transpeptidase activities aiming to evaluate the value of gamma GT in differentiation of icterus of various etiology. Comparing the values of the examined cholestase enzymes in patients of obstructive icterus it could be seen that gamma GT was positive in the largest percentage of the diseased, (69,6%), then APH (89,7%) AND LAP (86,3%). Gamma GT has shown to be selective test for obstruction of hepatobiliary tract but it is not selective for discovering cause of obstruction. It can be explained by the fact that activity of gamma GT could be found both in mechanical icterus caused by calculosis or tumours (with a very high activity) and in patients with hepatitis with cholestatic component, although in the decresed activity.