The availability of the gamma-labelled
bile acid 75SeHCAT, that allows a non-invasive assessment of the enterohepatic circulation of
bile acids, has prompted in the last 10 years the implementation of several studies involving wide series of normal subjects and patients with various organic and functional bowel disorders. The clinical indications for performing a
SeHCAT test have been clearly defined: the test can identify with high accuracy, in the setting of the
irritable bowel syndrome, the patients with
bile acid malabsorption that can be confidently and successfully treated with
cholestyramine; it can also assess whether, and to what extent, the diarrhoea presenting in patients with intestinal organic disorders is due to
bile acid malabsorption, permitting an optimal therapeutic strategy to be designed. The parameters of the hepatic handling of
SeHCAT after bolus
intravenous administration have been characterized in normals, and studies on various chronic hepatic disorders are now in progress. Interesting results are emerging from studies performed in patients with chronic non-obstructive cholestatic disease, where a specific defect in the excretion rate of
SeHCAT is present: these studies may cast more light on the abnormalities of bile secretion and on the mechanism of action of drugs used to treat this condition, forming the rationale for the use of intravenous
SeHCAT for hepatobiliary dynamic scintigraphy as a sophisticated liver function test. In conclusion, the
SeHCAT test has become an important diagnostic tool for the gastroenterologist studying the diarrhoea, and awaits more studies to be used also by the hepatologist. The relatively long physical half-life of 75Se (180 days), preventing a wider use of the test, could theoretically be overcome by the synthesis of a similar gamma-labelled
bile acid with a shorter half-life.