Black tarry stools can have various causes, ranging in severity from 'needs attention' to 'life-threatening'. Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.
Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms. In order to diagnose black tarry stools, we could:
|Possible Urgent Medical Need||97%||Confirm|
|Carcinoid Cancer||1%||Ruled out|
|Stomach Ulcers||0%||Ruled out|
Do you ever pass black, tarry stools?
Possible responses:→ No / don't know
→ Yes, sometimes slightly black/tarry
→ Yes, often slightly black/tarry, sometimes very
→ Yes, my stools are usually/always very black/tarry
Blood, as seen in the stool, can originate anywhere along the intestinal tract. A black stool (called melena) usually means that the blood is coming from the upper part of the tract. At least 4 Tablespoons (60ml) of blood must have been lost in order to make the stool black. Maroon-colored stools suggest that the blood is coming from the middle portion of the intestinal tract, and bright red from the large bowel or rectum. If stools change color suddenly, it can be evidence of internal bleeding which requires immediate medical attention.
The ingestion of black licorice, Pepto-Bismol, or blueberries can all cause black stools or false melena. Stools should be tested for the presence of hidden blood.
Significant blood in the stool from a carcinoid tumor can cause bowel movements to become black.
Bleeding from an ulcer may occur in the stomach or the duodenum, and sometimes is the only symptom. Rapid bleeding causes bowel movements to become black or even bloody.
Black, tarry stools usually result from bleeding that occurs high up in the digestive tract – for example, in the stomach or first segment of the small intestine (duodenum); blood in the stomach turns black when exposed to stomach acid and enzymes. A single severe bleeding episode can produce tarry stools for as long as a week, so continuing tarry stools do not necessarily indicate persistent bleeding.