Melena often results from damage to the upper GI tract lining, swollen blood vessels, or bleeding disorders.
The most common cause of melena is peptic ulcer disease, in which painful ulcers or sores develop in the stomach or small intestine. This can be caused by an infection of Heliobacter pylori (H. pylori), which damages the mucosal lining and can lead to ulcer development in the stomach and duodenum. Similarly, chronic use of aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) can also lead to gastritis and resultant ulcers of the GI tract.
Damage to the GI tract can result from various other conditions, such as Mallory–Weiss tears, which are tears in the lower esophagus typically caused by excessive vomiting. Additionally, conditions associated with acid production, such as gastroesophageal reflux disease (GERD), may cause severe inflammation of the esophagus known as erosive esophagitis, which in turn can lead to ulceration and consequent bleeding. In some cases, GI bleeding can be indicative of vascular lesions, such as angiodysplasia or Dieulafoy’s lesion, and even tumor development, including adenocarcinomas, squamous cell carcinomas, carcinoid tumors, and lipomas.
Swollen blood vessels, or varices, can also lead to upper GI bleeding. This most commonly occurs with portal hypertension, which refers to increased blood pressure in the portal vein. Liver disease such as cirrhosis, or liver scarring, can cause the blockage of blood flow through the liver, thus causing blood to back up in the portal vein, which then leads to increased pressure or portal hypertension. The increase in pressure can cause esophageal and gastric varices, which are fragile and bleed easily.
Blood disorders that are characterized by excessive bleeding and frequent bruising, such as hemophilia and thrombocytopenia, can also contribute to bleeding in the GI tract. Finally, taking anticoagulants, such as warfarin or direct oral anticoagulants (DOACs), can also predispose to GI bleeding.