Can bowel polyps cause blood in stool?

A bowel polyp is a growth from the inner lining of the large bowel or rectum. Some polyps have a fragile surface that can bleed as stool passes. The blood may be bright red, appear on toilet paper or the outside of stool, or be mixed into the stool. Small amounts may not be visible and can be detected only with a stool test.

The colour and amount of blood do not diagnose a polyp. Haemorrhoids, an anal fissure, inflammation, infection, diverticular disease and other bowel conditions can also cause bleeding. A clinician may consider your symptoms, examination findings, medicines and family history before deciding whether testing is needed.

Arrange a medical review for unexplained blood in stool, even when the amount is small or the bleeding stops. Note when it started, whether it was bright red or dark, where it appeared, and whether you also have a change in bowel habit, abdominal discomfort, tiredness or unintentional weight loss. Tell the clinician about medicines such as blood thinners and any previous bowel problems.

Assessment may include an abdominal or rectal examination, blood tests, stool testing or referral for a camera examination of the bowel. If a polyp is found during colonoscopy, it may be removed and sent for laboratory examination. The result helps determine whether further follow-up is appropriate.

Seek urgent medical help if bleeding is heavy or ongoing, the stool is black and tar-like, or you feel faint, confused, unusually weak or short of breath. Severe abdominal pain, repeated vomiting, a swollen abdomen or inability to pass stool or gas also needs prompt assessment. These features can signal significant bleeding or another acute bowel problem.

Ask what might be causing the bleeding and which test is most suitable. You can also ask whether your medicines should be adjusted before testing, how a detected polyp would be removed, when results are expected, and what follow-up would be recommended if a polyp is found.