Single most likely diagnosis
- Gastrointestinal bleeding from a peptic ulcer or gastritis, possibly triggered or exacerbated by certain foods. This is likely because black stool (melena) is a common presentation of upper GI bleeding, and certain foods can irritate the stomach lining or exacerbate existing conditions.
Other Likely diagnoses
- Iron supplements: Taking iron supplements can cause black stools due to the oxidation of iron.
- Certain medications (e.g., bismuth subsalicylate): Some medications, like those containing bismuth, can turn stools black.
- Food coloring or dyes: Consuming foods or drinks with dark coloring or dyes can temporarily turn stools black.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Upper GI malignancy: Although less common, black stools could be a sign of a gastrointestinal malignancy, such as stomach cancer, which would be critical to diagnose early.
- Variceal bleeding: Bleeding from esophageal varices, often due to liver cirrhosis, can present with melena and is a medical emergency.
Rare diagnoses
- Hemobilia: Bleeding into the biliary tree can cause black stools, although this is a rare condition.
- Angiodysplasia: Vascular malformations in the GI tract can cause bleeding and melena, but this is less common and typically seen in older adults.
- Ingested blood: In rare cases, eating blood (e.g., in some cultural or culinary practices) can cause black stools.