What are the causes of melena (black tarry stools)?

From the Guidelines

Black tarry stools, medically known as melena, are primarily caused by upper gastrointestinal bleeding, with the most common etiologies being duodenal ulcer, gastric erosions, gastric ulcer, varices, Mallory-Weiss tears, esophagitis, duodenitis, and neoplasm, as reported in the 2017 study by Singh-Bhinder et al 1. The causes of black tarry stools can be diverse, but they often originate from the upper gastrointestinal tract.

• Upper gastrointestinal bleeding (UGIB) is a significant cause of morbidity and mortality, with 100 episodes per 100,000 admissions annually in the United States and mortality rates as high as 14% 1.
• The most common etiologies of UGIB include duodenal ulcer, gastric erosions, gastric ulcer, varices, Mallory-Weiss tears, esophagitis, duodenitis, and neoplasm, with some patients having multiple sources of bleeding 1.
• Other potential causes of black tarry stools include iatrogenic causes such as endoscopic ultrasound-guided biopsies, endoscopic retrograde cholangiopancreatography–related injury, delayed hemorrhage from biliary metallic stenting, nitinol esophageal or upper GI stent placement for obstruction, and extrahepatic arterial injury after pancreatic surgery 1.
• Rare entities such as hemobilia and hemosuccus pancreaticus can also cause UGIB, with the latter estimated to be the responsible etiology in 1 of every 500 cases of UGIB 1.
• It is essential to seek immediate medical attention if experiencing black tarry stools, as this can indicate significant blood loss that may be life-threatening 1.

From the Research

Causes of Black Tarry Stools

• Black tarry stools, also known as melena, can be caused by various factors, including:
  • Gastrointestinal bleeding, which can be due to several conditions such as esophageal varices, gastric varices, or rectal varices 2, 3, 4
  • Portal hypertension, usually due to cirrhosis, which can lead to acute variceal bleeding 2, 3
  • Variceal hemorrhage, which is a substantial cause of morbidity and mortality, with esophageal and gastric varices being the most common source 3
• The exact cause of black tarry stools can vary, but it is often associated with bleeding in the upper gastrointestinal tract, such as:
  • Esophageal varices, which can bleed severely and have a high mortality rate 2, 3
  • Gastric varices, which are responsible for 10-30% of all variceal hemorrhage and tend to bleed more severely with higher mortality 4
• Other possible causes of black tarry stools may include:
  • Bleeding from other sources in the gastrointestinal tract, such as ulcers or tumors
  • Ingestion of certain substances, such as iron or bismuth, which can cause black stools
  • However, there is no direct evidence in the provided studies to support these claims, and the primary cause of black tarry stools appears to be related to gastrointestinal bleeding and variceal hemorrhage 2, 3, 4