What causes black tarry stools after a colostomy?

Possible causes of black, tarry stools (melena) after a colostomy could include:

- Retained stool or a blockage in the digestive system. This can cause blood to pool and become dark and tarry.

- Rectal bleeding. This could be caused by an injury to the rectum or colon during the colostomy procedure, or by a hemorrhoid or fissure.

- Underlying medical conditions. Certain conditions, such as an ulcer, diverticulitis, or cancer of the colon or rectum, can also cause black, tarry stools.

If you are experiencing black, tarry stools after a colostomy, it is important to seek medical attention right away. This could be a sign of a serious underlying medical condition that requires treatment. Your doctor can perform tests, such as a colonoscopy or endoscopy, to determine the cause of the bleeding and provide appropriate treatment.