Thorotrast-induced oro- and hypopharyngeal fibrosis with recurrent bleeding.

Thorium dioxide, widely used as a contrast material, is a producer of alpha particle radiation. This is well demonstrated by autoradiography. The case described illustrates that life-threatening, thorium dioxide-induced pharyngeal haemorrhage may occur even with an occluded carotid artery. The radiation exposure caused an intense foreign body reaction with a marked cell-deficient fibrosis. The alpha particles are well demonstrated by autoradiography. In addition, we were able to show a defect in the wall of the carotid artery due to the Thorotrast injection, which was closed by cell-depleted connective tissue. As the radioactivity of the nuclides of thorium dioxide peaks 30-40 years after its first application, the morbidity will increase and the disease has to be taken into careful consideration in head and neck tumour lesions.