Which 99mTc-labeled agent is preferred for demonstrating intermittent gastrointestinal bleeding?

The preferred option for demonstrating intermittent gastrointestinal bleeding is the use of red blood cells labeled with technetium-99m (99mTc). When assessing internal bleeding, particularly when it occurs intermittently, it is crucial to capture the moment when bleeding is happening.

Labeled red blood cells are particularly effective in this scenario because they circulate throughout the bloodstream and can actively accumulate in a bleeding site, providing a clear indication of the location and extent of hemorrhage. This method ensures that even small or transient episodes of bleeding can be detected since the labeled red blood cells will appear at the site of the bleed shortly after it occurs.

In contrast, other agents, such as human serum albumin, sulfur colloid, and lidofenin, are less effective for this indication. Human serum albumin is primarily used for evaluating vascular perfusion and does not localize to the site of bleeding as effectively as red blood cells. Sulfur colloid is useful for imaging the reticuloendothelial system and is typically used for liver and spleen scans, but it does not offer the sensitivity required for detecting active bleeding. Lidofenin is a cholescintigraphy agent that helps in the assessment of biliary pathology, not gastrointestinal bleeding.

Thus, the