Radioisotope methods used in the diagnosis of gastrointestinal bleeding

A brief survey of radionuclide methods for the diagnosis of gastrointestinal bleeding is presented. 51Cr-labelled erythrocytes are used to detect bleeding; labelling is performed in vitro. Two methods, using 99mTc-labelled erythrocytes and 99mTc-S-colloid, are conventional for the examination of the bleeding site. In the former, the activity administered is 400 to 600 MBq, and 99mTc is usually bonded to the erythrocytes in vivo. The latter method, based on the 99mTc-S-colloid, is more sensitive, allowing bleeding at flow rates as low as 0.05 to 0.1 ml/min to be detected. In examinations focusing on the Meckel diverticulum, 99mTc-pertechnetate is applied intravenously, the activity administered is about 3 to 7 MBq/kg, and about 200 MBq is typically administered. Practical applications of the methods are dealt with. The role of radionuclide techniques within the group of methods for the examination of gastrointestinal bleeding is discussed. (Z.S.). 6 refs