What does it mean to have black stool?

Generally speaking, passing black stool refers to melena. Black stool may be caused by factors such as food and medication effects, advanced age, stress ulcers, gastrointestinal bleeding, or Mallory-Weiss syndrome (esophageal-gastric mucosal laceration). If discomfort occurs, it is recommended to seek medical attention promptly. Specific causes are analyzed as follows:

1. Food and Medication Effects

Consuming large amounts of foods rich in iron or lead, or taking medications containing iron or bismuth—such as ferrous sulfate tablets, polysaccharide-iron complex capsules, or colloidal bismuth pectin capsules—may cause the stool to turn black. It is advisable to discontinue the related medications and adjust dietary habits by reducing intake of iron- or lead-rich foods.

2. Advanced Age

In elderly individuals, slowed gastrointestinal motility leads to prolonged retention of food residue in the intestines. This enhances bacterial decomposition and increases production of sulfides, which may darken the stool. Increasing dietary fiber intake to promote intestinal motility is recommended. Additionally, under medical guidance, medications such as lactulose oral solution, senna granules, or麻仁润肠丸 (Ma Ren Run Chang Wan) may be used for treatment.

3. Stress Ulcer

Following severe illness, surgery, or trauma, stress responses can damage the gastric mucosa and lead to ulcer formation, potentially causing melena. Symptoms may also include upper abdominal discomfort, pain, nausea, and vomiting. Treatment under a doctor's guidance may include pantoprazole sodium enteric-coated tablets, potassium citrate bismuth capsules, or rebamipide tablets.

4. Gastrointestinal Bleeding

Gastrointestinal bleeding is commonly caused by inflammation, ulcers, or other conditions within the digestive tract. When blood is exposed to gastric acid, it forms black ferric sulfide, leading to black-colored stools. This may be accompanied by symptoms such as abdominal pain, nausea, and vomiting. Patients should follow medical advice and use medications such as omeprazole enteric-coated capsules, thrombin lyophilized powder, or norepinephrine bitartrate injection for treatment.

5. Mallory-Weiss Syndrome (Esophageal-Gastric Mucosal Laceration)

Mallory-Weiss syndrome occurs due to severe vomiting or sudden increases in intra-abdominal pressure, resulting in tears in the mucosa at the gastroesophageal junction. This may lead to bleeding; as blood passes through the digestive tract, iron from hemoglobin reacts with gastric acid and intestinal bacteria to form ferrous sulfide, turning the stool black. Symptoms may also include vomiting and hematemesis (vomiting blood). Under medical guidance, patients may receive etamsylate injection, aminobenzoic acid injection, or tranexamic acid injection for treatment.

To help prevent black stools, it is advisable to avoid spicy, greasy, irritating foods, as well as hard, coarse, or difficult-to-digest foods, which may further irritate the gastrointestinal tract.