Vascular complications of thorium dioxide

Area of Science:

• Vascular Medicine
• Radiology
• Pathology

Background:

• Thorium dioxide (thorotrast) was historically used as a contrast agent in medical imaging.
• Long-term adverse effects of thorotrast exposure, particularly vascular complications, are not fully understood.
• Chronic alpha irradiation from retained thorotrast is a suspected cause of delayed pathology.

Observation:

• Two patients exposed to thorotrast developed severe late-onset vascular complications.
• One patient experienced cerebral and myocardial infarcts, succumbing at age 25.
• The second patient, aged 33, presented with asymptomatic complete right carotid artery obstruction due to a thorotrastoma.

Findings:

• Necropsy revealed significant adventitial and intimal fibrosis of the left carotid artery in the first patient.
• Severe luminal narrowing (over 75%) of the left main and left anterior descending coronary arteries was observed.
• The second patient's necropsy confirmed total obstruction of the right carotid artery attributed to a thorotrastoma.

Implications:

• Thorium dioxide exposure can lead to debilitating and fatal vascular complications years after administration.
• Chronic alpha irradiation from thorotrast is a likely mechanism driving these late vascular events.
• These findings underscore the importance of long-term surveillance for individuals with historical thorotrast exposure.