[Late complications of thorotrast. Experiences from Zurich]

57 cases of late sequelae after diagnostic thorotrast exposure (recorded between 1944 and 1982 in Zurich) are presented. The alpha-ray-emitting contrast medium thorotrast is carcinogenic and fibrogenic. Malignant tumors occurred in about half of our cases after a latency period of 14 to 44 years, comprising 8 primary liver carcinomas, 2 carcinomas of the bile ducts, 3 malignant hemangioendotheliomas of the liver, 10 renal pelvic carcinomas and sarcomas, and one acute myelogenous leukemia. Further, cirrhosis and fibrosis of the liver and paravascular "thorotrastoma" were observed. The late effects of thorotrast are a negative example of avoidable radiation injuries to man.