Detection of gastrointestinal bleeding with 99mTc-sulfur colloid.

We have developed a single scintigraphic technique to detect and localize the site of bleeding in the gastrointestinal tract. This examination requires only intravenous administration of 99m-Technetium sulfur colloid and imaging of the abdomen. Very shortly after the introduction of the radiopharmaceutical, a fraction of the injected activity extravasates at the bleeding site and is eliminated from the circulation. This phenomenon is repeated each time the blood recirculates adding another, but smaller fraction to the extravasated activity at the site of hemorrhage. Because of continued clearance of the radiopharmaceutical from the vascular pool by the reticuloendothelial system, a contrast is eventually reached between the site of bleeding and surrounding background. Based on animal experiments bleeding rates as low as .05-0.1 cc/min can be detected with this technique. The sensitivity of the approach in the detection of the site of hemorrhage is significantly higher than arteriography or other techniques which utilize radioactive blood pool indicators. We have mainly used this technique in the evaluation of patients with GI bleeding. In more than 25 patients with negative scintigrams for hemorrhage, arteriography showed no evidence of bleeding. In 38 patients with scintigraphic evidence of bleeding. In 38 patients with scintigraphic evidence of hemorrhage, arteriograms were positive for bleeding in les than 50% of the cases. No false positive results have been noted in the latter group. This technique appears to offer a simple, practical and reliable approach to the evaluation of patients with gastrointestinal bleeding.