Bowel bleeding is a popular term for rectal bleeding which refers to the passage of blood through the anus, either in stool or on its own. This may be noticed as blood in the stool, in the toilet bowl water or even blood upon wiping after defecation. In severe cases, the bleeding is spontaneous and can even soil a patient’s underwear. Most cases of bowel bleeding arise from the rectum and anal blood vessels in conditions like hemorrhoids. The blood is bright red and fresh which is known as hematochezia. Sometimes the blood may appear dark and old giving rise to black tarry stools which is known as melena.

Location of Bowel Bleeding

Melena typically indicates bleeding in the upper gut – esophagus, stomach and first parts of the small intestine. The bleeding is from the walls of the gut and due to the action of air and digestive enzymes, the blood degrades to appear black in color often with a slightly foul odor. Hematochezia indicates bleeding in the lower gut – ileum of the small intestine, colon, rectum or anus. Blood is bright red and still fluid and therefore easily evident when wiping.

However, there are certain instances where melena may be due to bleeding in the lower gut and hematochezia from the upper gut.

  • Constipation may slow the passage of colonic contents therefore bleeding in the colon may delay the exit. This leads to the degradation of blood and melena although it is a lower gut bleed.
  • Diarrhea causes rapid gastroesophageal motility so fresh blood from the upper gut is quickly passed out of the bowel. Therefore hematochezia in this case is from bleeding in the upper gut.

Bowel bleeding may be due to injury to the gut wall, infections, or even perforations and should always be treated as a serious sign. Although the majority of cases is due to hemorrhoids and is not serious, it is however distressing and needs to be attended to. Chronic bowel bleeding, even a light bleed, can lead to anemia. Severe acute bowel bleeding can lead to hypovolemic shock and even progress to death.

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Article reviewed by Dr. Greg. Last updated on April 23, 2011