What Does Melena Represent?
Melena is the passage of black, tarry stools that indicates the presence of digested blood in the gastrointestinal tract, most commonly originating from bleeding proximal to the ligament of Treitz (the upper GI tract). 1
Clinical Significance and Source of Bleeding
Melena specifically represents upper gastrointestinal bleeding in the vast majority of cases, with the upper GI tract being the most common source (approximately 85-90% of cases). 1, 2
The black, tarry appearance occurs because blood has been digested by gastric acid and intestinal enzymes as it passes through the GI tract, requiring approximately 50-100 mL of blood and several hours of transit time. 1
In patients with obscure GI bleeding presenting with melena, the bleeding source is twice as likely to be in the proximal small intestine compared to those without melena. 3
Most Common Causes
The primary etiologies of melena include: 1
- Peptic ulcer disease (35-50% of cases) - most common cause in Western populations
- Gastroduodenal erosions (8-15%)
- Esophageal varices (5-10%) - higher proportion in certain populations, particularly those with cirrhosis
- Esophagitis (5-15%)
- Mallory-Weiss tears (15%)
- Upper GI malignancy, vascular malformations, and other rare causes (collectively <10%)
Clinical Presentation and Severity
Patients presenting with both hematemesis (vomiting blood) and melena typically have more severe bleeding than those with melena alone. 1
Melena is the most common presenting symptom of upper GI bleeding, occurring more frequently than hematemesis in clinical practice. 4
Approximately 10-15% of patients presenting with apparent lower GI bleeding (hematochezia) actually have an upper GI source with rapid transit. 1
Critical Management Implications
Hospital evaluation is mandatory for melena because: 5
Mortality rates for admitted patients with GI bleeding range from 2-14%, with higher rates (33%) in those who develop bleeding while hospitalized for other conditions. 1
Esophagogastroduodenoscopy (EGD) is the primary diagnostic and therapeutic procedure of choice, ideally performed within 24 hours of presentation after hemodynamic stabilization. 1, 5, 6
Early specialist intervention in hospital settings significantly reduces mortality compared to delayed treatment. 5
Key Clinical Predictors
Factors suggesting the bleeding source will be identified on EGD include: 2
- Presence of vomiting
- Abnormal abdominal imaging findings
- Hemoglobin level ≥3 g/dL below normal limits
Important Caveats
Not all black stools are melena - iron supplements, bismuth subsalicylate, and certain foods can cause black stools without blood present. 1
In patients with confirmed melena where EGD is negative, small bowel capsule endoscopy should be considered as the small intestine accounts for 0.7-9% of cases. 1, 2
Elderly patients (>65 years) and those with significant cardiovascular, renal, or hepatic comorbidities have substantially higher mortality rates and require more aggressive management. 5