Premature extravasation. A bleeding site identified during the dynamic phase of Tc-99m red blood cell bleeding scintigraphy.

Tc-99m RBC scintigraphy is favored by many investigators because it provides the ability to image the abdomen over a prolonged period of time, thereby allowing identification of delayed bleeding sites that are frequently encountered due to the intermittent nature of gastrointestinal bleeding. The authors describe a case of bleeding scintigraphy with labeled red blood cells in which the bleeding site was identifiable only on the dynamic blood-flow and first static images. On later images, the labeled blood cells had spread throughout the colon, rendering localization of the actual bleeding site impossible. Two previous red blood cell scintigraphies and a subsequent contrast angiogram did not reveal sites of active bleeding. As illustrated by this unusual case, factors governing timing and visualization of abnormal bleeding sites are discussed, as is a differential diagnosis of abnormal foci of activity seen on the dynamic phase of bleeding scintigraphy.