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What are the Causes of Blood in the Stool?

Depending on the location of the bleeding in the gastrointestinal tract, the colour of the blood may vary. Generally, the closer the bleeding site is to the anus, the brighter red the blood will be. Thus,

  • Bright red blood usually indicates bleeding low in the colon or rectum (lower GI)
  • Dark red or maroon blood usually indicates bleeding higher in the colon or the small bowel (upper GI)
  • Melena usually means bleeding in the stomach (bleeding from ulcers) or duodenum and has characteristic black, tarry (sticky), and foul smell.

With bleeding from the upper GI tract and depending on how long the blood remains in the stomach and small intestine, the color in the stool will change from bright red to maroon, to black. Blood in the stool that is red or maroon is most commonly is referred to as rectal bleeding.

Following diseases or conditions may commonly cause blood in stool:

  • Anal fissures: A small cut or tear in the tissue lining the anus caused by passing a large, hard stool. Each subsequent bowel movement can cause severe pain. Bleeding is a result of trauma to the existing tear.
  • Hemorrhoids: Hemorrhoids, commonly known as Piles primarily occurs due to the swollen fissures in your rectum or anus.
  • Cancers and polyps of the rectum and colon: When the normal growth and division of the cells lining the large bowel multiply, it results in the formation of a polyp(s). Polyps that become large can bleed.
  • Diverticulosis: Sometimes small pouches (diverticuli) form in weakened sections of intestine lining and protrude through the bowel wall, usually in the sigmoid colon. Bleeding occurs as a complication of diverticulosis.
  • Abnormal blood vessels in the lining of the intestines (angiodysplasia): Angiodysplasia is vascular malformation of the gut. The fragile blood vessels cause bleeding.
  • Colitis: Inflammation of the colon due to infection or inflammatory bowel disease is known as colitis. It can be ulcerative, Crohn’s, infectious or Ischemic type of colitis.


A physical examination will be performed by the physician. If necessary, diagnostic tests may be ordered.

Physical exam: The focus is on finding the source and extent of bleeding. Priority is to identify significant low blood volume and begin appropriate treatment. This is the most life-threatening situation. The physician will focus on three aspects:

1.Vital signs: Low blood pressure and elevated heart rate will indicate a significant loss of blood. An elevated temperature will suggest infection.

2.Abdominal examination: The physician will search for abdominal distension, discomfort, or tenderness that may suggest a possible bleeding ulcer. A mass the doctor can feel is cause for concern about cancer.

3.Anal and digital rectal examination: The anus will be inspected for possible external sources of bleeding such as trauma, foreign body, or hemorrhoids. A finger examination is performed to assess tenderness, the character of stool, and the presence of masses.

Diagnostic tests: Depending on the type and severity of bleeding, special tests may be performed to aid in diagnosis.

Blood tests: Blood samples are taken to assess the extent of blood loss, the clotting ability of blood, and the possibility of infection.

Nasogastric tube: A flexible tube is passed through the nose into the stomach to check for the presence of active bleeding. This may be uncomfortable, but can be a vital diagnostic test.

Scope examinations:

  • Anoscopy: A plastic or metal scope placed into the anus allows for quick examination of the rectal vault.
  • Flexible sigmoidoscopy: A flexible tube inserted into the rectum is used to evaluate the rectum and lower end of the colon.
  • Colonoscopy: A soft tube equipped with a light and camera is inserted into the rectum and pushed into the colon. The entire large colon is visualized. It is used to locate areas of bleeding, masses, or irregularities.
  • Barium enema X-ray: This study uses liquid barium inserted into the rectum. An X-ray is taken to highlight problem areas such as tumours or diverticula. However, sites of active bleeding cannot be distinguished.
  • Nuclear medicine studies: A tagged red blood cell scan may be used to pinpoint areas of slow bleeding.
  • CT scan: May be used to diagnosing diverticulitis or tumours in the bowel.
  • Angiography: A contrast dye study is used to evaluate active areas of brisk bleeding.
  • Radionuclide scans: There are two types of radionuclide scans that are used for determining the site of gastrointestinal bleeding; a Meckel’s scan, and a tagged red blood cell (RBC) scan.


The treatment of blood in stools depends on the cause of the bleeding.

  • Bleeding due to diverticular disease, colitis or angiodysplasia may resolve spontaneously without intervention. However, recurrent bleeding may require endoscopic therapy, and severe massive life-threatening bleeding may sometimes even require surgery.
  • Haemorrhoids are generally treated with a combination of lifestyle and dietary advice, medications and/ or rubber band ligation of the haemorrhoids. This is done in the outpatient clinic. Surgery may be performed if the bleeding is recalcitrant in spite of medical therapy.
  • Bleeding as a result of colorectal cancer should be managed with surgery for the primary tumour
  • Vasoconstrictors: This medicine decreases the size of blood vessels and helps stop the bleeding.
  • Iron supplement: Iron helps body make more red blood cells.
  • Steroids: This medicine decreases inflammation in the rectum. It may be applied as a cream, ointment, or lotion.
  • IV: To compensate dehydration. Extra liquids recommended.
  • Blood transfusion: Blood is tested for diseases, such as hepatitis and HIV, to be sure it is safe.
  • Surgery: To remove hemorrhoids, tumours, or polyps.

If you or your near or dear ones spot blood in the stool, consult our specialized doctor at CMC, Mohali to seek help and treatment.