Does anal cancer cause blood in stool?

Anal cancer can irritate or damage tissue near the anus, causing bright red blood on toilet paper, on the outside of stool, or in the toilet. Bleeding may occur with a lump, pain, itching, discharge, changes in bowel habit, or a feeling of incomplete emptying. These symptoms can overlap with haemorrhoids, anal fissures, infection, or bowel conditions.

The colour, amount, timing, and recurrence of bleeding help a clinician decide what to examine. A visible bleeding source should not be self-diagnosed, particularly when it persists or is accompanied by a change in bowel function.

Arrange a medical appointment for unexplained, repeated, or persistent blood in stool. Note whether it is bright red or dark, mixed through the stool or on its surface, and whether pain, constipation, diarrhoea, weight change, or a lump is present. A clinician may inspect the area and recommend further tests. Avoid delaying assessment because you suspect haemorrhoids.

Seek emergency help for heavy or continuous bleeding, black tarry stool, fainting, severe abdominal or anal pain, confusion, or marked weakness. Get prompt medical advice when bleeding is accompanied by dizziness, worsening pain, a new lump, or a significant change in bowel habits.

Ask what may be causing the bleeding, whether the anus and rectum need examination, and which tests could clarify the cause. Ask which changes to stool or bowel habit should be reported immediately and when follow-up should occur.