Gastroenterologic and radiologic approach to obscure gastrointestinal bleeding: how, why, and when?

Gastrointestinal (GI) bleeding is a common clinical condition that is increasingly seen in an aging population and frequently requires hospitalization and intervention, with significant morbidity and mortality. Obscure GI bleeding (OGIB) is defined as loss of blood with no source identified after upper endoscopy and colonoscopy. Whether an obscure site of bleeding is clinically evident or silent, it constitutes a diagnostic and therapeutic challenge for the clinician. Gastroenterology and radiology provide the essential diagnostic tools used to evaluate suspected OGIB, each with its strengths and weaknesses. Small bowel series and conventional enteroclysis have a limited role in OGIB. Computed tomographic (CT) enterography and CT enteroclysis are noninvasive techniques with promising results in evaluation of small bowel disease and silent OGIB. CT angiography is a useful triaging tool for diagnosing or excluding active GI hemorrhage, localizing the site of bleeding, and guiding subsequent treatment. Tagged red blood cell scanning is the most sensitive technique for detection of active GI bleeding and allows imaging over a prolonged period, making it useful for detecting intermittent bleeding. Capsule endoscopy has emerged as an important tool for investigating OGIB, but it may soon have competition from double-balloon enteroscopy, a diagnostic technique that can also facilitate therapy.