Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for medical concerns, especially in emergency conditions like black stools (melena).
Melena refers to the passage of black, tarry, foul-smelling stool, usually indicating upper gastrointestinal (GI) bleeding. It is a medically significant symptom that often requires urgent evaluation.
In most cases, melena develops when blood is exposed to gastric acid and digestive enzymes, turning it black before passing through the intestines.
What Is Melena?
Melena is a clinical term used to describe black-colored stool resulting from bleeding in the upper part of the gastrointestinal tract, typically above the ligament of Treitz. The black color is caused by the oxidation of iron in hemoglobin as blood is digested.
Unlike fresh blood in stool (hematochezia), melena usually suggests bleeding from the esophagus, stomach, or duodenum.
Why Does Stool Turn Black in Melena?
When bleeding occurs in the upper GI tract, hemoglobin from red blood cells reacts with stomach acid. This chemical process converts iron into hematin, which gives stool its characteristic black, tar-like appearance.
Even a small amount of upper GI bleeding can cause melena, whereas lower GI bleeding usually causes red or maroon-colored stool.
Common Causes of Melena
- Peptic ulcer disease (gastric or duodenal ulcers)
- Gastroesophageal varices (commonly in liver disease)
- Gastritis or erosive esophagitis
- Upper GI malignancies (stomach or esophageal cancer)
- Medications such as NSAIDs, aspirin, or anticoagulants
- Severe physiological stress (stress ulcers)
Symptoms Associated With Melena
Melena itself is a symptom, but it may be accompanied by other clinical signs, including:
- Weakness or fatigue
- Dizziness or fainting
- Shortness of breath
- Abdominal pain
- Vomiting blood (hematemesis)
- Pallor due to anemia
Warning: Melena with low blood pressure, rapid pulse, or confusion is a medical emergency.
Diagnosis of Melena
Diagnosis focuses on identifying the source of bleeding. Common investigations include:
- Complete blood count (CBC) to detect anemia
- Stool occult blood test
- Upper gastrointestinal endoscopy (gold standard)
- Liver function tests (if liver disease suspected)
- Imaging studies when indicated
Treatment of Melena
Treatment depends on the underlying cause and severity of bleeding:
- Endoscopic therapy to control bleeding
- Proton pump inhibitors (PPIs)
- Blood transfusion in severe anemia
- Management of liver disease or varices
- Surgical intervention in refractory cases
Early treatment significantly reduces complications and mortality.
When Should You See a Doctor?
Seek immediate medical attention if you notice:
- Black, tarry stools
- Vomiting blood
- Sudden weakness or collapse
- History of liver disease or ulcers with melena
Prevention and Risk Reduction
- Avoid unnecessary NSAID use
- Limit alcohol consumption
- Treat Helicobacter pylori infection
- Regular follow-up for chronic liver disease
Frequently Asked Questions (FAQ)
Is melena always a medical emergency?
Melena often indicates serious upper GI bleeding and should always be evaluated urgently.
Can iron supplements cause black stool?
Yes, iron supplements can darken stool, but they do not cause tarry consistency or foul odor like melena.
How is melena different from hematochezia?
Melena is black stool from upper GI bleeding, while hematochezia is fresh red blood usually from lower GI sources.
Can melena resolve on its own?
No. Even if bleeding stops temporarily, the underlying cause must be diagnosed and treated.
Related Articles (Internal Links)
- Gastrointestinal Disorders
- Liver Disease and Complications
- Understanding Anemia
- Endoscopy Procedures