Diagnostic Approach to Abnormal Stool Color

Initial Clinical Assessment

The American Gastroenterological Association recommends assessing for associated symptoms: abdominal pain, weight loss, hemodynamic instability, or signs of anemia in patients with abnormal stool color 2, 3
A digital rectal examination should be performed to evaluate for hemorrhoids, anal fissures, or palpable masses, as recommended by the American Gastroenterological Association 3, 4
The American College of Gastroenterology suggests examining all hernia orifices and surgical scars for potential obstruction 5

A complete blood count is strongly recommended for all patients with stool color changes to assess for anemia, according to the American Gastroenterological Association 2, 3, 4
Stool hemoccult testing is recommended if bleeding is suspected, as suggested by the American Gastroenterological Association 2
The European Society for Clinical Nutrition and Metabolism recommends C-reactive protein or erythrocyte sedimentation rate testing if an inflammatory process is suspected 7

The American Gastroenterological Association recommends that all patients with melena require sigmoidoscopy at minimum 8, 9, 6
The American College of Gastroenterology suggests that full colonoscopy or air-contrast barium enema is indicated for patients with dark blood or blood mixed in feces, guaiac-positive stools, anemia, age >50 years without recent colorectal cancer screening, or family history of colorectal cancer or personal history of polyps 8, 9, 6, 1
The American Society for Gastrointestinal Endoscopy recommends anoscopy to visualize internal hemorrhoids and flexible sigmoidoscopy mandatory even if hemorrhoids identified for bright red blood 8, 9, 1

The American College of Emergency Physicians recommends assessing hemodynamic stability immediately and obtaining IV access, initiating fluid resuscitation if unstable in patients with melena 10
The American Gastroenterological Association suggests inserting a nasogastric tube to assess for upper GI source and transfusing packed red blood cells to maintain hemoglobin >7 g/dL (>9 g/dL if massive bleeding or cardiovascular disease) in patients with melena 5, 10
The American College of Gastroenterology recommends proceeding urgently to upper endoscopy if melena is confirmed and considering colonoscopy if upper endoscopy is negative 6, 1