Black diarrhea, a dark, tarry, and often foul-smelling stool discoloration, can be unsettling. While it may signal a serious underlying health concern, it can also result from dietary choices or medications. Understanding its cause is important for appropriate action.
Potential Causes of Black Diarrhea
Black diarrhea, medically termed melena, indicates bleeding in the upper gastrointestinal (GI) tract (esophagus, stomach, or first part of the small intestine). Its black, tarry consistency and distinct, strong odor result from hemoglobin in the blood being altered by digestive enzymes and intestinal bacteria during digestion.
Common medical conditions causing melena include bleeding peptic ulcers (sores in the stomach or duodenum lining). Inflammation of the stomach (gastritis) or esophagus (esophagitis) can also cause bleeding, as can esophageal varices (swollen veins in the esophagus, often linked to liver disease). Less common but serious causes include Mallory-Weiss tears (esophageal lining tears from severe vomiting) or cancers of the esophagus, stomach, or pancreas.
Black stool is not always due to internal bleeding; non-medical causes exist. Certain foods, like black licorice, blueberries, or dark chocolate, can temporarily turn stool black. Medications such as bismuth subsalicylate (in some antidiarrhea remedies) or iron supplements also cause dark stool. Stool discoloration from these sources usually lacks the tarry consistency and foul odor of melena.
Accompanying Symptoms to Watch For
When black diarrhea signals internal bleeding, other serious symptoms may accompany it. These include abdominal pain, especially from an ulcer, and nausea or vomiting, sometimes with vomit resembling coffee grounds, indicating upper digestive tract bleeding.
Significant blood loss can cause dizziness, lightheadedness, or fainting due to low blood pressure. Other symptoms include fatigue, weakness, a rapid heart rate, or shortness of breath.
When to Seek Medical Attention
Seek medical attention if black diarrhea appears. Immediate emergency care is necessary if the black stool is tarry, sticky, foul-smelling, and accompanied by severe symptoms like dizziness, lightheadedness, fainting, severe abdominal pain, or vomiting blood. These symptoms indicate significant blood loss requiring urgent intervention.
Even without severe symptoms, contact a healthcare provider for non-urgent evaluation if black stool persists for over a day or two, or if its cause is unclear. This is especially true if the color change doesn’t resolve after discontinuing medications or supplements known to cause dark stool.
How Black Diarrhea is Diagnosed
Diagnosis of black diarrhea begins with a detailed medical history, including recent diet, medications, and other symptoms. A physical examination checks for abdominal tenderness. Initial assessment often includes tests to detect blood in the stool and assess blood loss.
A fecal occult blood test detects hidden blood in stool. Blood tests, like a complete blood count, check for anemia, indicating significant blood loss. If upper GI bleeding is suspected, an esophagogastroduodenoscopy (EGD) is performed. This procedure uses a thin, flexible tube with a camera to visualize the esophagus, stomach, and duodenum, allowing doctors to locate and sometimes treat the bleeding source. If the source is unclear or lower GI issues are suspected, a colonoscopy may examine the large intestine.
Treatment Approaches
Treatment for black diarrhea depends on its underlying cause. If due to diet or medications, discontinuing the substance usually resolves the issue, with stool color returning to normal within a day or two.
For medical causes, particularly upper gastrointestinal bleeding, interventions stop bleeding and treat the condition. Endoscopic procedures during an EGD can seal bleeding sites using electrocautery, medication injection, or clips. Medications like proton pump inhibitors may reduce stomach acid, aiding ulcer or inflammation healing. For severe blood loss, transfusions or intravenous fluids may restore blood volume. In rare, severe cases, surgery might address the bleeding source.