What happens if bowel cancer is not treated?

As a bowel tumour grows, it may narrow the passage and change bowel habits. Symptoms can include blood in the stool, abdominal pain, bloating, constipation, diarrhoea, vomiting, or a feeling that the bowel has not emptied. Ongoing bleeding can contribute to anaemia and tiredness. The cancer may extend into nearby tissues or lymph nodes and can travel through the bloodstream, including to the liver. The effects and speed of change vary with the tumour’s site, type, and stage.

A bowel symptom does not by itself prove cancer; many digestive conditions cause similar changes. Diagnosis requires appropriate assessment rather than guessing from symptoms.

Arrange review with a colorectal or oncology team. Tests may include colonoscopy, scans, biopsy, and genomic tumour profiling when it can help guide therapy. Depending on the findings, care may involve bowel resection, chemotherapy, radiotherapy, targeted treatment, or a combination. Ask how the plan addresses the tumour, bowel function, nutrition, and any spread to the liver or other organs.

Go to urgent care for severe or worsening abdominal pain, repeated vomiting, a swollen abdomen, inability to pass stool or gas, black stools, heavy rectal bleeding, fainting, or marked weakness. These can signal obstruction, bleeding, or another complication that needs immediate assessment.

Ask where the cancer is located, whether it has reached lymph nodes or the liver, which tests are needed, whether surgery is suitable, how bowel function may change, and which symptoms should prompt an emergency call.