Noninvasive Evaluation of Active Lower Gastrointestinal Bleeding: Comparison Between Contrast-Enhanced MDCT and 99mTc-Labeled RBC Scintigraphy

OBJECTIVE. The purpose of our study was to compare contrast-enhanced MDCT and Tc-99m-labeled RBC scanning for the evaluation of active lower gastrointestinal bleeding. SUBJECTS AND METHODS. Over 17 months, 55 patients (32 men, 23 women; age range, 21-92 years) were evaluated prospectively with contrast-enhanced MDCT using 100 mL of iopromide 300 mg I/mL. Technetium-99m-labeled RBC scans were obtained on 41 of 55 patients and select patients underwent angiography for attempted embolization. Each imaging technique was reviewed in a blinded fashion for sensitivity for detection of active bleeding as well as the active lower gastrointestinal bleeding location. RESULTS. Findings were positive on both examinations in eight patients and negative on both examinations in 20 patients. Findings were positive on contrast-enhanced MDCT and negative on Tc-99m-labeled RBC in two patients; findings were negative on contrast-enhanced MDCT and positive on Tc-99m-labeled RBC in 11 patients. Statistics showed significant disagreement, with simple agreement = 68.3%, K = 0.341, and p = 0.014. Sixteen of 60 (26.7%) contrast-enhanced MDCT scans were positive prospectively, with all accurately localizing the site of bleeding and identification of the underlying lesion in eight of 16 (50%). Nineteen of 41 (46.3%) Tc-99m-labeled RBC scans were positive. Eighteen of 41 matched patients went on to angiography. In four of these 18 (22.2%) patients, the site of bleeding was confirmed by angiography, but in 14 of 18 (77.8%), the findings were negative. CONCLUSION. Contrast-enhanced MDCT and Tc-99m-labeled RBC scanning show significant disagreement for evaluation of active lower gastrointestinal bleeding. Contrast-enhanced MDCT appears effective for detection and localization in cases of active lower gastrointestinal bleeding in which hemorrhage is active at the time of CT.