Blood in the stool: when to see a gastroenterologist

What the colour can suggest

Bright red blood on the stool, on tissue paper or in the toilet bowl usually comes from the lower part of the bowel or the anus. Dark, black or tar-like stools with a strong smell can point to bleeding higher up, in the stomach or food pipe.

Colour is only a clue. It does not confirm the cause, and a doctor needs to examine you.

Common causes

• Piles (haemorrhoids)
• A small tear around the anus (fissure), often with pain and constipation
• Infection or inflammation of the bowel
• Polyps in the large intestine
• Ulcers or other problems in the stomach and upper digestive tract
• Less often, growths in the bowel that need early diagnosis

Who should see a gastroenterologist

• Anyone with blood in the stool that returns or does not settle
• A change in bowel habit that lasts more than a few weeks
• Blood along with weight loss, tiredness or looking pale
• A family history of bowel problems or bowel cancer
• Blood in the stool at an older age, even if you think it is piles

How colonoscopy helps

A colonoscopy lets the doctor look directly at the lining of the large intestine and rectum with a thin, flexible camera. It can show the source of bleeding, find inflammation, and identify polyps, which can often be removed during the same procedure.

Not everyone with blood in the stool needs one. The specialist decides after examination and your history, and explains the reason if it is advised.

What to expect at the consultation

The doctor will ask how long the bleeding has been present, its colour and amount, and any pain or bowel changes. Blood tests may be advised to check for anaemia, and the examination may include a check around the anus.