Black Stool (Melena)

Definition

Melena is distinct from hematochezia (red/maroon stool from lower GI bleeding) and hematemesis (vomiting blood). - Harrison's Principles of Internal Medicine 22E, p.360

Key Distinction: True Melena vs. False Black Stool

Causes

Upper GI Bleeding (most common cause of melena)

Small Bowel Bleeding

Bleeding from the small intestine often presents with prolonged occult blood loss but can cause melena if GI transit times are long. - Rosen's Emergency Medicine, p.3361

Initial Evaluation

History

• Duration and quantity of black stool
• Associated hematemesis (suggests UGIB)
• NSAID/aspirin/anticoagulant use
• Alcohol use, cirrhosis, portal hypertension
• Prior peptic ulcer disease or GI surgery
• Symptoms of hemodynamic compromise (dizziness, syncope, chest pain, dyspnea)

Hemodynamic Assessment (first priority)

• Tachycardia at rest suggests ~15% blood volume loss
• Orthostatic hypotension suggests ~20-30% loss
• Shock (BP <90 mmHg) suggests >30% loss

Nasogastric Lavage

• Bloody return confirms UGIB
• Clear return does not exclude UGIB (up to 16% false negative)

Labs

• CBC (hemoglobin, platelet count)
• BMP (BUN elevated from blood digestion - BUN:Cr ratio >30 supports UGIB)
• Coagulation (PT/INR, aPTT)
• Type and crossmatch
• Liver function tests (if varices suspected)

Management

Resuscitation (stabilize first)

1. Two large-bore IVs; IV fluids (normal saline or LR)
2. Transfuse PRBCs: target Hgb >7 g/dL (>9 g/dL in active cardiac disease or varices)
3. Correct coagulopathy (FFP, vitamin K if INR elevated)
4. Platelets if <50,000

Medical Therapy

• PPI (IV): IV pantoprazole/omeprazole bolus + infusion for suspected peptic ulcer bleeding (reduces rebleeding and mortality in high-risk ulcers)
• Octreotide: IV infusion for suspected variceal bleeding (reduces portal pressure); continue 2-5 days
• Antibiotics (ceftriaxone): Standard in cirrhotic patients with variceal bleeding - reduces infection risk and mortality

Endoscopy (EGD)

• Should be performed within 24 hours of presentation in most cases (within 12 hours in hemodynamically unstable or suspected varices)
• Both diagnostic and therapeutic

Endoscopic Therapy Options

• Ulcers with active bleeding or visible vessel: Bipolar electrocoagulation, heater probe, epinephrine injection, hemostatic clips, or topical hemostatic powder
• Varices: Endoscopic band ligation (esophageal); tissue adhesive injection or TIPS (gastric)
• Mallory-Weiss tears: Endoscopic ligation if actively bleeding

Refractory/Recurrent Bleeding

• TIPS (transjugular intrahepatic portosystemic shunt): For refractory variceal bleeding; also first-line for Child-Pugh B/C patients with active variceal hemorrhage
• Interventional radiology (angiographic embolization): When endoscopy fails
• Surgery: Reserved for massive ongoing bleeding not controlled endoscopically

Prevention of Recurrence

• H. pylori eradication: Reduces rebleeding from peptic ulcers to <5%
• Discontinue NSAIDs if bleeding ulcer; if NSAIDs must be continued, use COX-2 inhibitor + PPI
• Aspirin for secondary cardiovascular prevention: Do NOT discontinue; restart promptly after hemostasis (early reinstitution associated with lower 8-week mortality: 1% vs 13%)
• Long-term PPI: For ulcers unrelated to H. pylori or NSAIDs (42% rebleeding rate at 7 years without therapy)
• Beta-blockers + endoscopic ligation: For variceal bleeding prophylaxis

Prognosis

• Overall case fatality ~2% for all GIB hospitalizations
• Inpatient mortality: ~10% for UGIB, ~4% for LGIB
• Patients most often die from decompensation of underlying comorbidities rather than exsanguination

Melena in Bedridden Patients

Why Bedridden Patients Are at Higher Risk

1. Stress-Related Mucosal Disease (SRMD)

Endoscopic evidence of upper GI bleeding from SRMD is common, even shortly after admission, in high-acuity ICU patients. The pathophysiology is impaired mucosal protection, mostly related to blood flow, and not acid hypersecretion or H. pylori infection. - Mulholland & Greenfield's Surgery 7E

2. Medications Common in Bedridden Patients

• NSAIDs / ketorolac: frequently used for pain; disrupt prostaglandin-mediated mucosal protection
• Anticoagulants (heparin, warfarin, DOACs): used for DVT prophylaxis; amplify bleeding
• Corticosteroids: combined with NSAIDs markedly increases risk
• Antiplatelet agents: aspirin, clopidogrel

3. Diagnostic Challenges

• Patients may be intubated, sedated, or cognitively impaired - cannot report symptoms
• Melena may be mistaken for normal dark stool, especially with iron supplements or enteral formulas
• Hemodynamic changes (tachycardia, hypotension) may be masked by vasopressors or beta-blockers
• Nasogastric tube in place may detect bloody aspirate before formal melena appears

Clinical Presentation Clues

• Black tarry stool on rectal exam or noted on diaper/pad change
• Coffee-ground material in nasogastric aspirate
• Unexplained drop in hemoglobin (>2 g/dL)
• Rising BUN out of proportion to creatinine (BUN:Cr >30 suggests digested blood)
• Hemodynamic deterioration (tachycardia, hypotension) in absence of other cause

Management

Resuscitation

• IV access, fluid resuscitation
• Transfuse PRBCs: target Hb >7 g/dL (>9 g/dL in active cardiac ischemia)
• Correct coagulopathy: FFP, vitamin K, platelets if <50,000
• Hold/reverse anticoagulants as clinically appropriate (weigh DVT/PE risk)

Pharmacologic

• IV PPI (pantoprazole 80 mg bolus + 8 mg/hr infusion, or 40 mg IV BID): first-line for suspected peptic/stress ulcer bleeding
• IV octreotide: if variceal bleeding suspected (cirrhotic patient)
• Antibiotics (e.g., ceftriaxone): if cirrhosis present

Endoscopy

• Upper endoscopy (EGD) within 24 hours (within 12 hours if hemodynamically unstable)
• May be technically challenging but feasible in intubated patients
• Provides both diagnosis and treatment

Stress Ulcer Prophylaxis (Prevention)

Who Should Receive Prophylaxis?

• Coagulopathy, shock, or chronic liver disease - give SUP (conditional recommendation)
• Mechanical ventilation alone - no longer considered a firm independent indication
• Enterally fed patients at high risk - suggest SUP; at low risk, suggest no SUP
• Discontinue when ICU risk factors resolve; do NOT continue on ward transfer without active indication

What Agent?

• PPI or H2 receptor antagonist (H2RA) - either acceptable; use low-dose regimens
• Sucralfate is less preferred than PPI/H2RA
• The 2024 NEJM Evidence meta-analysis (9,533 patients, 12 RCTs) confirmed PPIs reduce clinically important UGIB by 49% (RR 0.51, 95% CI 0.34-0.76; high certainty). However, PPIs may increase mortality in the most severely ill patients (possible signal; low certainty) - reinforcing targeted rather than blanket prophylaxis.
• A 2026 meta-analysis (Awan et al., Dig Dis 2026) flags increased C. difficile risk with PPIs in ICU patients - another reason not to over-prescribe.

Role of Enteral Nutrition

• Early enteral feeding likely reduces UGIB risk in ICU patients by maintaining mucosal integrity and perfusion
• The 2024 SCCM guideline notes enteral nutrition as a probable protective factor - when feasible, prefer enteral over parenteral nutrition

Prophylaxis against SRMD is indicated for patients requiring mechanical ventilation >48 hours or with coagulopathy. Either PPIs or H2 antagonists can be used. There may be a role to avoid pharmacologic agents even in highest-risk patients if they are being enterally fed. - Mulholland & Greenfield's Surgery 7E

Special Considerations

Summary