Cyanomelana

Cyanomelana is a term used in medicine to describe dark blue to black discoloration of the feces. This appearance is typically caused by the presence of certain substances in the diet or by the administration of medications. It is important to distinguish cyanomelana from melena, which is the passage of dark, tarry stools that indicates digested blood, a sign of gastrointestinal bleeding.

Dietary causes of dark stools resembling cyanomelana include the consumption of large quantities of dark-colored foods such as blueberries, blackberries, or black licorice. Ingesting iron supplements, particularly ferrous sulfate, can also lead to very dark or black stools. Similarly, certain medications, including bismuth-containing compounds like Pepto-Bismol, are known to cause a black discoloration of the stool.

While generally benign and related to intake, it is always advisable to consult a healthcare professional if new or unexplained changes in stool color occur. They can help determine the cause and rule out any underlying medical conditions, especially if other symptoms such as abdominal pain, nausea, vomiting, or changes in bowel habits are present. A medical history and physical examination, possibly including stool tests, can confirm the source of the discoloration.