Melena

Melena refers to black stools that occur as a result of acute gastrointestinal bleeding in the upper gastrointestinal (GI) tract. The upper GI tract includes the mouth, esophagus, stomach, and the first part of the small intestine, called the duodenum. In some cases, slow bleeds in the ascending colon of the large intestine, which is located in the lower GI tract, can also result in melena. 

Melena should not be confused with hematochezia, which refers to fresh blood in the stools that leads to maroon or bright red-colored stools. This blood typically comes from the lower GI tract, most often from rectal bleeding, such as hemorrhoids or an anal fissure. 

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. 

Signs and symptoms that may be seen with melena vary depending on the amount of blood loss and the source of bleeding. Significant blood loss can lead to symptoms of low blood volume, such as weakness, shortness of breath, low blood pressure and tachycardia, clammy skin, and dizziness of confusion, in severe cases.   

Individuals with mild blood loss often only experience symptoms associated with the source of bleeding. For example, individuals with peptic ulcers may report upper abdominal pain, pain with eating, or dyspepsia, whereas those with a Mallory-Weiss tear may report severe epigastric or back pain and have a history of vomiting or retching. Individuals with esophagitis may have pain in the lower chest area and report trouble swallowing or sometimes food impaction. On the other hand, those with gastroesophageal varices may have signs of chronic liver disease such as jaundice, enlarged liver or spleen, or ascites. Finally, individuals with GI tumors usually present with decreased appetite, weight loss, anemia, or a positive fecal occult blood test. 

Diagnosis or treatment begins by identifying the source(s) of bleeding in order to determine and treat the underlying cause. An assessment of the individual’s medical history is performed to identify potential causes, such as chronic NSAID use. A nasogastric lavage (also known as the pumping of stomach contents) can be used to determine the severity of blood loss and to prepare the GI tract for endoscopy, which is a minimally invasive procedure used to look inside the body. An upper endoscopy will often be performed to determine the exact source of bleeding.  

Medication therapy with proton pump inhibitors (PPIs), such as esomeprazole or pantoprazole, can help reduce acid production, which encourages the healing of peptic ulcers and thus reduces the risk of recurrent bleeding. Proton pump inhibitors, along with antibiotics, can also be used to treat H. Pylori infection, which is another potential cause of melena.  

If necessary, the bleeding can be controlled through a combination of endoscopic therapies. The most commonly performed being injection therapy, in which medication is injected directly into the source of bleeding to promote coagulation (i.e., blood clotting). This is often combined with other endoscopic therapies, such as thermal techniques that apply heat probes to cauterize the bleeding or mechanical techniques that apply pressure, using devices like clips or rubber band ligation. 

In some cases, angiographic embolization may be performed, in which medication or coils are placed onto a guided catheter to block blood flow at the location of bleeding. Surgery can also be used to stitch up ulcers or lacerations. Finally, severe cases of melena may require blood transfusions and supportive treatment with IV fluids due to the amount of blood loss.