Visualization of portal venous collaterals on a technetium-99m labeled red blood cell scan for gastrointestinal bleeding. Potential pitfall in interpretation

A Tc-99m labeled red blood cell study was performed on a patient with carcinoma of the colon and gastrointestinal bleeding. This demonstrated an unusual pattern of collateral circulation due to extrahepatic obstruction of the portal venous system by recurrent carcinoma. This pattern could be easily mistaken for small bowel loops and represents a potential pitfall in image interpretation. It emphasizes the importance of a flow study and comparison with later images.