How should I evaluate and manage a patient presenting with black, tarry stool (melena)?

Evaluation and Management of Black Stool (Melena)

Admit the patient to the hospital immediately for hemodynamic assessment, resuscitation, and urgent esophagogastroduodenoscopy (EGD) within 24 hours, as melena represents upper gastrointestinal bleeding with significant mortality risk that requires early specialist intervention. 1

Initial Assessment and Stabilization

Hemodynamic Evaluation

• Check vital signs immediately: pulse >100 bpm, systolic blood pressure <100 mmHg, or hemoglobin <100 g/L indicates severe bleeding requiring intensive monitoring 1, 2
• Establish two large-bore IV lines in the anticubital fossae and begin aggressive fluid resuscitation with 1-2 liters of normal saline 1, 2
• If shock persists after 2 liters, add plasma expanders as this indicates ≥20% blood volume loss 1, 2
• Insert urinary catheter to measure hourly urine output (target >30 ml/h indicates adequate resuscitation) 1, 2
• Consider central venous pressure monitoring in patients with significant cardiac disease (target CVP 5-10 cm H₂O) 1

Confirm True Melena vs. Benign Black Stool

• True melena has a black, tarry appearance with sticky consistency and characteristic odor, indicating blood exposed to gastric acid 3
• Simple black stools from dietary causes (iron supplements, bismuth subsalicylate, black licorice, blood-containing foods) lack the tarry quality and odor 3, 4
• Obtain detailed medication and dietary history to exclude non-bleeding causes 1, 3
• Melena typically requires at least 50-100 mL of blood loss to produce visible symptoms 3

Blood Transfusion Strategy

• Transfuse red blood cells to maintain hemoglobin >7 g/dL 1, 2
• Use higher threshold of >9 g/dL in patients with massive bleeding or cardiovascular comorbidities 1, 2

Risk Stratification

High-Risk Features Requiring Aggressive Management

• Age >65 years (mortality up to 30% in those >90 years) 1, 3
• Hemodynamic instability despite resuscitation 1, 2
• Presence of both hematemesis and melena (indicates more severe bleeding than melena alone) 3
• Significant comorbidities: cardiovascular disease, renal insufficiency, liver disease, or advanced malignancy (strongest predictor of death) 1
• Heart rate >100 bpm plus systolic BP <100 mmHg confers ≈80% risk of ongoing bleeding or death when combined with active ulcer bleeding 1

Cirrhosis Assessment

• Specifically assess for cirrhosis, as variceal bleeding mortality approaches 30% versus 10% for nonvariceal sources 1, 2
• Cirrhotic patients require prophylactic antibiotics and vasoactive medications 2
• Consider early TIPS placement in Child-Pugh class C (score 10-13) or class B with active bleeding despite vasoactive agents 1

Diagnostic Approach

Esophagogastroduodenoscopy (EGD)

• EGD is the initial procedure of choice as it has both diagnostic and therapeutic capabilities 1
• Perform within 24 hours after achieving hemodynamic stability 1, 3, 2
• Critical pitfall: Never perform endoscopy before adequate resuscitation in unstable patients, as this increases mortality 1, 2
• Keep patient fasted until hemodynamically stable 1, 2
• In severely bleeding patients, consider endotracheal intubation before endoscopy to prevent pulmonary aspiration 1
• Use cap-fitted endoscopy to examine blind areas (high lesser curve, under incisura angularis, posterior duodenal bulb) 1

Common Causes Identified on EGD

• Peptic ulcer disease (35-50% of cases, associated with Helicobacter pylori or chronic NSAID use) 1, 2
• Gastroduodenal erosions (8-15%) 2
• Esophageal varices (5-10%, but up to 42.5% in some populations) 1, 2, 5
• Mallory-Weiss tears (15%) 1, 2
• Esophagitis (5-15%) 2

When EGD is Negative

• Perform colonoscopy, as approximately 10-15% of patients presenting with melena have a lower GI origin 1
• Lower GI sources include diverticulosis (20-41% of cases in older adults), angiodysplasia (3-40%), ischemic colitis (10-21%), and colorectal cancer/polyps (6-27%) 1
• If both EGD and colonoscopy are negative, proceed to capsule endoscopy to identify small intestinal bleeding lesions 1
• Angiodysplasia accounts for up to 80% of obscure bleeding, particularly in patients over 40 years 1
• Small bowel tumors are the most common cause in patients under 50 years 1
• Consider double-balloon enteroscopy for therapeutic intervention if a lesion is identified 1

Rare but Critical Causes to Consider

• Aortoenteric fistula in patients with prior abdominal aortic aneurysm repair 1
• Cameron's erosions in large hiatal hernias 1
• Dieulafoy's lesion (large caliber artery in stomach wall) 1
• Hemobilia and hemosuccus pancreaticus (≈1 in 500 cases) 1

Post-Endoscopy Management

Therapeutic Interventions

• Following successful endoscopic therapy in patients with ulcer bleeding, administer high-dose proton pump inhibitor therapy 1
• Address underlying causes: Helicobacter pylori eradication, acid suppression, and counsel regarding NSAID use 1, 2

Monitoring for Rebleeding

• Rebleeding is defined by fresh hematemesis/melena plus hemodynamic instability (pulse >100 bpm, systolic pressure <100 mmHg), CVP fall >5 mmHg, or hemoglobin reduction >20 g/L over 24 hours 2

Special Considerations

Anticoagulation Management

• In hemodynamically stable patients on anticoagulation (especially DOACs like apixaban), the first therapeutic step is correction of the coagulopathy 1
• All DOACs elevate baseline bleeding risk and should be prescribed cautiously in patients with known GI pathology 1

Very Low-Risk Patients

• Very low-risk young patients with minor bleeding, no hemodynamic compromise, and no high-risk features may be discharged without endoscopy after appropriate evaluation 1, 2
• However, hospital admission is the standard approach given significant mortality rates for GI bleeding 1