Four patients with gastrointestinal bleeding identified by a modified in vivo technique with labeled red blood cells sedimentation.

OBJECTIVE Gastrointestinal bleeding scintigraphy (GIBS) offers the advantage of continuous monitoring of patients to localize the site of gastrointestinal bleeding. In this study, a modified in vivo labeling method with sedimentation of the labeled red blood cells (RBC) was applied to remove free technetium-99m (99mTc) and increase labeling efficiency. PATIENTS AND METHODS Four patients were studied. A modified in vivo RBC labeling method was used. After 10 minutes of RBC sedimentation, patients' blood plasma in the upper part of the syringe was removed, and the erythrocytes labeled with 99mTc were re-administered to the patient. Serial dynamic scintiphotos were taken during the first 60 minutes. Delayed static images were acquired up to 22 hours after injection. RESULTS The labeling efficiency of 99mTc-RBC increased up to 93%. GIBS can be performed after 20 hours post-injection and provide accurate diagnosis of gastrointestinal bleeding. No false positive findings due to free 99mTc accumulation were observed for the four patients. CONCLUSION The modified in vivo method with sedimentation is a simple and effective way to increase the labeling efficiency and thus the diagnosis for the detection of gastrointestinal bleeding.