What happens if rectal cancer is not treated?

Rectal cancer can enlarge within the bowel and cause bleeding, narrowing, or changes in bowel habits. Extension into nearby tissues may produce pelvic discomfort or affect bladder and sexual function. If the bowel becomes severely narrowed, abdominal swelling, vomiting, and inability to pass stool or gas can occur. Cancer cells may also travel through lymphatic or blood vessels to organs such as the liver or lungs. The pace differs between people, and staging scans, biopsy findings, and examination help the team understand the extent.

Ask for review by a colorectal surgeon and oncology team, even if you are uncertain about treatment. Options may include radiotherapy, chemotherapy before surgery, removal of the affected rectal segment, or a stoma to divert stool. The order depends on tumour location, stage, symptoms, and your health. Tell the team about bleeding, bowel changes, weight changes, pain, medicines, and any concerns about continence or living with a stoma.

Seek urgent assessment for heavy or ongoing rectal bleeding, severe abdominal pain, repeated vomiting, a swollen abdomen, fever with worsening symptoms, or inability to pass stool or gas. New dizziness, fainting, or marked weakness alongside bleeding also needs immediate care.

Ask where the tumour is located, whether it has narrowed the bowel, what staging tests are needed, why treatment is offered in a particular order, and whether a temporary or longer-term stoma may be needed.