Diagnostic Approach to Lower Gastrointestinal Tract Bleeding

Initial Assessment and Diagnostic Algorithm

The American Gastroenterological Association recommends that the first test performed in a patient with lower GIT bleeding is anoscopy, especially when bright red rectal bleeding is present, as this may indicate an anorectal source of hemorrhage 1, 2
For hemodynamically unstable patients, the European Society of Gastrointestinal Endoscopy suggests that CT angiography (CTA) should be the first-line investigation as it provides the fastest and least invasive means to localize the bleeding site 3, 4
The American College of Gastroenterology recommends that CTA is preferred over colonoscopy in unstable patients as it can identify bleeding sources in the upper GI tract or small bowel, is widely available, and requires no bowel preparation 2, 5
For hemodynamically stable patients, the American Gastroenterological Association recommends that direct anorectal inspection with anoscopy should be performed first, especially when bright red rectal bleeding is present, allowing for immediate identification of common anorectal sources such as hemorrhoids, which account for approximately 14% of lower GIT bleeding 1, 6, 7

The International Society for the Study of Upper Gastrointestinal Disease notes that approximately 10-15% of apparent lower GIT bleeding may have an upper GI source, and considers upper GI endoscopy if CTA is negative 7
The European Society of Gastrointestinal Endoscopy recommends that for patients with suspected small bowel bleeding after negative upper and lower endoscopy, video capsule endoscopy should be considered, although the exact percentage of cases is not specified 7
The American College of Gastroenterology suggests that failing to consider an upper GI source in patients with severe hematochezia and hypovolemia (10-15% of cases) is a common pitfall to avoid 7
The American Gastroenterological Association recommends that proceeding directly to colonoscopy without first examining the anorectal region, potentially missing easily identifiable sources, should be avoided 1, 6
The European Society of Gastrointestinal Endoscopy notes that using nasogastric tube placement to rule out upper GI bleeding is not reliable and is not routinely recommended 10
The American College of Gastroenterology recommends that delaying appropriate imaging in unstable patients while attempting bowel preparation for colonoscopy should be avoided 4, 9