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EDITOR’S QUIZ: GI SNAPSHOT

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From question on page 774

The patient had thorotrastosis and as a result developed hyposplenism and a hepatocellular carcinoma.

The computed tomography section demonstrated a poorly defined mass of low attenuation posteriorly in the right lobe of the liver. There was curvilinear high density material posteriorly within the lesion (fig 2, black arrow). There were also multiple small foci of high attenuation seen distributed in the region of the coeliac axis and splenic hilum (small white arrows) which were too dense to represent calcification, and the spleen was hypoplastic with the normal splenic parenchyma replaced by punctate high attenuation material (large white arrow). Note the normal splenic flexure anterior to the spleen containing oral contrast given prior to computed tomography. The appearances are those of thorotrastosis with a likely associated hepatic malignancy. Although serum alpha fetoprotein was normal, guided biopsy of the hepatic lesion confirmed the diagnosis of hepatocellular carcinoma. The patient later underwent right hepatectomy successfully but later died following local recurrence of the tumour.

Thorotrast was used as an x ray contrast agent from 1930 to 1955 before it was withdrawn. It was comprised of thorium dioxide (ThO2) and Th232, a naturally occurring alpha emitting radionuclide with a physical half life of 1.34×1010 years. Thorotrast was taken up by the reticuloendothelial system and due to its long half life was hardly eliminated from the body resulting in alpha irradiation of tissues in which it was deposited (thorotrastosis). Thorotrast has been shown to be associated with a wide range of radiation related malignancies. Cholangiocarcinoma, hepatocellular carcinoma, and angiosarcoma are the main associated types of liver cancer, usually occurring 20 years or more following initial exposure and there is also an association with liver cirrhosis.

Thorotrast deposits can be identified on plain radiograph or computed tomography as foci of high density, mirroring its distribution within the reticuloendothelial system. The thorotrast identified within the spleen in this patient rendered him hyposplenic and hence prone to pneumococcal infection, for which he received subsequent vaccination. Howell-Jolly bodies were present on the blood film. On further examination of previous records it became apparent that the patient had undergone a thorotrast arteriogram in 1951 as part of the investigations for the birthmark on his right leg.

Figure 2

 Computed tomography of a section through the right lobe of the liver and spleen demonstrating a poorly defined mass of low attenuation posteriorly in the right lobe of the liver. There was curvilinear high density material posteriorly within the lesion (black arrow). There were also multiple small foci of high attenuation seen distributed in the region of the coeliac axis and splenic hilum (small white arrows) which were too dense to represent calcification, and the spleen was hypoplastic with the normal splenic parenchyma replaced by punctate high attenuation material (large white arrow).

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