Evaluation and Management of Melena

Diagnostic Approach

The American College of Gastroenterology recommends that melena be diagnosed clinically by visual inspection and digital rectal examination, with management proceeding directly to hemodynamic assessment and endoscopy without waiting for laboratory confirmation of blood in stool 1, 2
Melena is a clinical diagnosis defined by the characteristic black, tarry, sticky appearance with a distinctive odor that indicates digested blood from the gastrointestinal tract 3
Digital rectal examination to confirm melena and exclude anorectal pathology is the only stool-related assessment needed 1

Calculate the shock index (heart rate/systolic blood pressure) immediately—a value >1 indicates hemodynamic instability 1
Check for orthostatic hypotension, which indicates significant blood loss requiring ICU admission 1
Perform digital rectal examination to confirm the presence of melena 1

For hemodynamically stable patients, calculate the Oakland score (includes age, gender, previous lower GI bleeding admission, digital rectal findings, heart rate, systolic BP, and hemoglobin) 1
Clinical predictors of increased risk include age older than 65 years, shock, poor overall health status, comorbid illnesses, low initial hemoglobin level, and fresh red blood on rectal examination 4

For hemodynamically unstable patients (shock index >1), perform CT angiography immediately—this provides the fastest, least invasive means to localize active bleeding 1
For hemodynamically stable patients, perform upper endoscopy (esophagogastroduodenoscopy) first, as melena typically indicates upper GI bleeding 1, 2
Esophagogastroduodenoscopy has both diagnostic and therapeutic capabilities and should be performed within 24 hours 2, 3

Do not delay endoscopy to obtain stool studies—melena is a clinical diagnosis that warrants immediate evaluation 1, 2
Failure to consider upper GI source in patients presenting with melena and hemodynamic instability leads to delayed diagnosis—always perform upper endoscopy first 1
Do not confuse simple black stools (from dietary iron, bismuth, or other causes) with true melena—the latter has a distinctive tar-like consistency and odor 3
Massive upper GI bleeding can present as bright red blood per rectum (hematochezia) rather than melena if transit time is rapid enough 3

Angiectasia is the most common cause of obscure bleeding, accounting for up to 80% of small bowel sources, particularly in patients with melena 5
Small bowel tumors are an important consideration in patients younger than 50 years with melena 5
Chronic NSAID or anticoagulant use increases the risk of peptic ulcer disease in patients with melena 6
Alcohol abuse has direct toxic effects on the intestinal epithelium and increases the risk of peptic ulcer disease in patients with melena 6

Up to 13% of melena cases are due to small intestinal bleeding when upper endoscopy is nondiagnostic, highlighting the importance of considering small bowel sources 5
Capsule endoscopy should be considered for obscure bleeding if upper endoscopy and colonoscopy are negative, as it can help diagnose small bowel sources 5

The American College of Radiology recommends performing EGD within 24 hours as the initial diagnostic procedure for hemodynamically stable patients with melena, which successfully identifies the bleeding source in 95% of cases and facilitates therapeutic intervention 7
EGD within 12 hours of presentation increases the likelihood of identifying a bleeding source, with an odds ratio of 3.71 (95% CI, 1.05-13.08) 7
The European Society of Gastrointestinal Endoscopy suggests that if EGD is nondiagnostic, colonoscopy should be performed as the next diagnostic step, as recommended by the Alimentary Pharmacology and Therapeutics society 8, 9

Colonoscopy identifies a suspected bleeding source in only 4.8% of patients with melena after nondiagnostic EGD, with an odds ratio of 2.17 (95% CI, 1.65-2.86) 8, 9
Therapeutic intervention during colonoscopy occurs in only 1.7% of these cases, highlighting the importance of careful patient selection for colonoscopy, as recommended by the Gastroenterology society 10

Patients with melena are at increased risk of colorectal cancer, with an odds ratio of 2.87 (95% CI, 1.82-5.51), making colonoscopy valuable even with low bleeding source identification, as noted by the Alimentary Pharmacology and Therapeutics society 8, 9
Capsule endoscopy should be considered for obscure bleeding after negative EGD and colonoscopy, as recommended by the Gastroenterology society, particularly in cases where small bowel bleeding is suspected 10