False-positive interpretations in technetium-99m sulfur colloid imaging for gastrointestinal bleeding

Radionuclide imaging with technetium-99m sulphur colloid (Tc-99m SC) is a commonly used method for demonstrating sites of active gastrointestinal bleeding. However since the capacity of the liver and spleen to phagocytize the large dose of Tc-99m SC used in the bleeding study is rapidly exceeded, extensive and rapid phagocytosis is seen in the bone marrow. In the normal subject, this uptake in the bony pelvis appears uniform and symmetrical. Two case reports of patients given Tc-99m SC are described, one with Paget's disease involving the right ilium and the other who had previously had a bone graft taken from his left ilium. Both patients showed a unilateral increase in pelvic bone marrow activity in the pelvis which was at first thought to offer evidence of a site of active bleeding in the lower abdomen. (U.K.)