Gastrointestinal bleeding is a frequent cause of hospital admissions. Patients present with melena, hematemesis, hematochezia, and/or shock. GI hemorrhage usually stops spontaneously or responds to conservative management. In approximately 25% of cases, however, the hemorrhage is massive and will be stopped only if the bleeding site is localized.1
Endoscopy is the principal method of diagnosing and treating GI hemorrhage. When endoscopy is impossible or ineffective, diagnostic imaging is recommended to localize the site of bleeding and determine its cause.2 GI bleeding is typically intermittent, and imaging must be timed appropriately.
The rate and pattern of the patient’s bleeding will determine which tests to use. Scintigraphic red blood cell scanning can detect bleeding rates of 0.2 to 0.4 mL/min.3 Screen-film angiography can detect bleeds of 0.5 mL/min in animal models. In vitro digital subtraction angiography is five to nine times more sensitive.4 The sensitivity of scintigraphy ranges from 20% to 60%. The accuracy of localization is relatively low, ranging from 41% to 54%.5 Arteriography has reported sensitivities that range between 22% and 87%, but its localization accuracy is excellent (100%).6
Multislice CT is emerging as a useful tool for the detection and localization of gastrointestinal bleeding. The principal finding of active bleeding is contrast extravasation in the bowel lumen with attenuation greater than 90 HU. Secondary signs include arterial enhancement or bowel wall thickening and the depiction of tumors or vascular lesions. Reported sensitivity and specificity rates for MSCT are 90.9% and 99%, respectively. Accuracy is 97.6%.7
