Observation of portal circulation through superior mesenteric vein by enteric coated capsule of thallium-201

A new method of oral administration of an enteric coated capsule of ²⁰¹Tl (²⁰¹Tl-capsule) was developed to evaluate the portal circulation through the superior mesenteric vein (SMV). The ²⁰¹Tl-capsule was not collapsed in the artificial gastric juice, whereas it melted soon after soaking in the artificial intestinal juice. In a clinical trial of 42 cases, ²⁰¹Tl was satisfactory released in the duodenum in 36 cases where clear liver images were observed except in 1 patient. Heart to liver ratio (H/L) at 60 or 90 min after duodenal release of ²⁰¹Tl was 0.32±0.07 (mean±1 s.d.) in normal controls, 0.34±0.12 in chronic hepatitis, 0.31±0.12 in acute hepatitis, 0.45±0.13 in liver cirrhosis and 0.48±0.32 in cirrhosis with hepatocellular carcinoma. In 11 patients who had both oral and rectal studies with ²⁰¹Tl, 7 showed a high H/L ratio of more than 0.8 in the rectal study but only 1 showed a similarly high ratio of 1.07 in the oral study. In the group of varied liver disorders we have studied so far, it was found that most of the SMV blood flowed into the liver and the degree of portal systemic shunting (PSS) from the SMV was much smaller compared to that from the inferior mesenteric vein. The present study with oral administration of the ²⁰¹Tl-capsule was of value in understanding portal circulation through the SMV, however, this technique seemed of limited usefulness for evaluating overall pathologic PSS.