When to Worry About Change in Bowel Habits With Bowel Cancer

Bowel-habit changes can include constipation, diarrhoea, alternating constipation and diarrhoea, narrower stools, more frequent bowel movements, or an urgent need to open your bowels. Most people with Bowel Cancer notice change in bowel habits. The pattern can vary with the location of a tumour and may also be affected by medicines, chemotherapy, radiotherapy, diet, reduced activity, infection, or dehydration. A symptom alone cannot show which cause is responsible.

Pay attention to what is different from your usual pattern and whether the change is getting worse, returning repeatedly, or occurring with abdominal discomfort, bloating, vomiting, tiredness, or blood mixed with or coating the stool.

Contact your oncology or colorectal team about a change that is new, persistent, worsening, or difficult to manage. Keep a short record of stool frequency, consistency, colour, blood, pain, fever, vomiting, food and fluid intake, and medicines such as laxatives or anti-diarrhoeal drugs. Do not start or stop bowel medicines without checking the treatment plan, especially if you have severe pain, vomiting, or a swollen abdomen.

Your clinician may review your medicines, examine your abdomen, check hydration, and decide whether blood tests, stool tests, imaging, or another bowel assessment is appropriate.

Seek urgent medical help for heavy or ongoing rectal bleeding, black or tar-like stools, severe or rapidly worsening abdominal pain, repeated vomiting, a markedly swollen abdomen, faintness, confusion, or inability to pass stool or gas. These signs can indicate bleeding, dehydration, infection, or bowel blockage and need prompt assessment.

If symptoms are milder but continue, call your cancer team promptly rather than waiting for the next routine appointment. Follow any emergency instructions your treatment centre has given you.

Ask: Could this change be related to my cancer or treatment? Which symptoms should make me call the oncology team immediately? What bowel medicines are suitable for me? How should I manage fluids and food while this is being assessed? Do I need an examination or tests?