Colorectal Cancer Screening

Overview

Bowel cancer screening means checking people who feel well for early signs of cancer in the large bowel (the colon and rectum). Screening looks for tiny amounts of blood in your stool (poo) or for small growths called polyps. Polyps are fleshy lumps on the inside wall of the bowel. Most polyps are harmless, but some can turn into cancer over many years. Finding and removing them early can stop cancer from starting, or catch it when it is easiest to treat.

Bowel cancer is one of the most common cancers worldwide, so screening programmes are offered to large numbers of people. Because it is common, screening is one of the most effective ways to protect your health as you get older.

Bowel cancer can affect anyone, but it is much more common in people over 50. Most national screening programmes invite people from around age 50 to 74, though the exact ages vary by country. Some people are offered screening earlier, for example if a close relative had bowel cancer, or if you have a condition such as inflammatory bowel disease (long-term inflammation of the bowel) or an inherited condition like Lynch syndrome (an inherited gene change that raises cancer risk).

Symptoms

Common symptoms

• Blood in your poo, or blood on the toilet paper after wiping
• Poo that looks dark or black and tarry
• A change in how often you poo, or in how firm it is, lasting three weeks or more, such as loose stools or constipation
• A feeling that your bowel has not emptied properly, even after going
• Tummy pain or cramping that keeps coming back
• Bloating or a swollen feeling in your tummy
• Losing weight without trying
• Feeling very tired, breathless, or looking pale (signs of anaemia, which means low iron in the blood)

Symptoms in children

• Bowel cancer is extremely rare in children, but children can get similar symptoms from much more common causes such as constipation or infection.
• See a doctor if a child has blood in their poo, ongoing tummy pain, or poor weight gain.
• In children, symptoms like these are almost always caused by something minor. A doctor can check and reassure you.

Symptoms in older adults

• Symptoms can be easier to miss in older adults, especially if a change in bowel habit is put down to getting older or to long-standing constipation.
• New tiredness, mild breathlessness, or low iron on a blood test should be checked, as these can be the first sign of bowel cancer in older people.
• Unexplained weight loss or a drop in appetite is always worth mentioning to your doctor.

Causes

Main causes

• Bowel cancer usually starts as a small polyp (a fleshy growth on the bowel wall). Over many years, changes in the cells inside the polyp can turn it into cancer.
• The exact reason any one person develops bowel cancer is often not known. It is usually a mix of age, genes, and lifestyle.
• Some cancers are linked to inherited gene changes, such as Lynch syndrome, which runs in families.
• Long-term inflammation of the bowel, as in inflammatory bowel disease (Crohn's disease or ulcerative colitis), can raise the risk over many years.

Risk factors

• Getting older, especially over 50
• A close relative (parent, sibling, or child) who had bowel cancer or polyps
• An inherited condition such as Lynch syndrome or familial adenomatous polyposis (a rare condition that causes many polyps)
• Long-standing inflammatory bowel disease
• Eating a lot of processed meat and red meat, and not much fibre
• Being overweight or living with obesity
• Smoking
• Drinking a lot of alcohol
• Not being physically active
• Type 2 diabetes
• Having had polyps removed before, or having had bowel cancer in the past

When to see a doctor

See a doctor urgently if:

• You see blood in your poo or on the toilet paper
• Your poo looks black and tarry
• Your bowel habits have changed and lasted three weeks or more
• You are losing weight without trying
• You feel very tired, breathless, or look pale
• You can feel a lump or swelling in your tummy
• You have heavy bleeding from your back passage or feel faint

Book a routine appointment if:

• Your screening test kit has arrived and you are not sure how to use it — your pharmacist, doctor's office, or screening service can explain
• Your screening result was unclear or you missed the return date and want to know what to do next
• You have a family history of bowel cancer and want to ask whether you should be screened earlier
• You have ongoing bloating, mild tummy discomfort, or a change in your usual pattern that worries you but is not getting worse
• You want to talk about lowering your risk through diet, weight, smoking, or alcohol

Diagnosis

Screening usually starts with a home stool test. You collect a small sample of poo on a stick or in a tube and post it to a lab. The lab checks for tiny traces of blood you cannot see. In the UK and many other countries this is called a FIT test (faecal immunochemical test). If the test shows blood, you will be offered a colonoscopy. A colonoscopy is a camera test that looks all the way around the inside of your bowel. It can find polyps and remove them during the same test. If anything looks suspicious, a tiny piece is taken as a biopsy (a small sample sent to the lab) to check under a microscope.

Tests that may be done

• FIT (faecal immunochemical test): a home stool test that looks for hidden blood
• Colonoscopy: a thin, flexible tube with a camera checks the whole bowel; small polyps can be removed at the same time
• Flexible sigmoidoscopy: a shorter camera test that looks at the lower part of the bowel
• CT colonography: a scan that builds pictures of the bowel, sometimes used instead of colonoscopy
• Biopsy: a small tissue sample checked in the lab to see if cells are normal
• Blood tests: to check for low iron or anaemia and to see how your general health is

What to expect at your appointment

The home test is quick and private — you do it at home and post it back. For a colonoscopy, you will be asked to follow a special diet and take a strong laxative the day before so your bowel is clean. You can usually have a sedative (medicine to help you relax) or pain relief. The test takes about 30 to 45 minutes. You will need someone to take you home afterwards, and you should not drive or work for the rest of the day. You may feel bloated or pass wind for a few hours. Results are usually ready within a few weeks, and the team will explain clearly what happens next.

Treatment

Screening often leads to treatment that is simple and preventive. If polyps are found during a colonoscopy, they are usually removed straight away, and that can be the whole treatment. If cancer is found, treatment depends on its size, position, and whether it has spread. A team of specialists will discuss your options with you and agree a plan together.

Self-care at home

• Do the screening kit as soon as it arrives, and post it back before the deadline on the letter
• Follow the instructions exactly — a spoiled or out-of-date sample may need to be repeated
• Keep a note of your screening results and the date of your next test
• If you are preparing for a colonoscopy, follow the diet and laxative instructions carefully; a clean bowel gives clearer pictures
• Arrange for someone to collect you and stay with you for 24 hours if you are having sedation
• Tell your doctor about any medicines you take, especially blood thinners, before a camera test

Medical treatments

If polyps are found, they are usually removed during the colonoscopy using a small wire loop or forceps. This is not surgery and you can often go home the same day. If cancer is found, treatment may include surgery, chemotherapy (medicine that kills cancer cells), radiotherapy (high-energy x-rays that target cancer cells), or newer treatments that help your immune system fight cancer. Your specialist team will explain which options suit your situation, along with the benefits and the possible side effects. They will also talk with you about taking part in research studies if you wish.

When is surgery considered?

Surgery is usually the main treatment when bowel cancer is found and has not spread far. The surgeon removes the part of the bowel containing the cancer, along with nearby lymph nodes (small glands that are part of your immune system). In many cases the two ends of the bowel are joined back together. Some people need a temporary or permanent stoma (an opening on the tummy where poo collects in a bag). Living well with a stoma is very possible, and specialist nurses help you adjust. Surgery may be done with keyhole (laparoscopic) methods, which means smaller cuts and a faster recovery for many people.

Living with this condition

For most people, screening is a brief task that gives peace of mind. If a polyp is removed, you may be invited back for a repeat check in a few years, depending on what was found. If you are treated for cancer, life may change for a while — appointments, recovery from surgery, and possibly a stoma — but many people return to work, hobbies, and normal routines. Your GP and specialist nurses can help with practical issues such as travel, work, and money worries.

Lifestyle tips

• Eat plenty of fibre: wholegrains, beans, lentils, fruit, and vegetables
• Limit processed meat and red meat; choose fish, chicken, or plant proteins more often
• Stay active — aim for something you enjoy most days, even a brisk walk
• Keep to a healthy weight if you can; your GP can offer support
• If you smoke, ask about stop-smoking support; it is one of the best things you can do for your health
• Keep alcohol within low-risk limits, and have several alcohol-free days a week
• Go for your screening tests when invited, even if you feel well
• Write down questions before appointments and take someone with you if that helps

Diet and exercise

A balanced diet and regular movement help your whole body, not just your bowel. Try to build meals around vegetables, beans, and wholegrains, and drink enough water. Gentle, regular exercise — like walking, swimming, or gardening — helps with energy, mood, and recovery after treatment. There is no special diet that guarantees protection from bowel cancer, so aim for small, steady changes you can keep up rather than a strict plan.

Mental health and emotional wellbeing

Waiting for a screening result or a camera test can make you feel anxious. That is completely normal. Many people feel relieved once they have their result, even if it means a follow-up test. If you are living with cancer or recovering from treatment, it is common to feel low, worried, or exhausted at times. Talking helps — to family, friends, your GP, or a counsellor. If you ever feel you cannot cope, or you have thoughts of harming yourself, please reach out for help right away: contact your local emergency number, your GP, or a crisis support line in your country.

Prevention

Not every case of bowel cancer can be prevented, but you can lower your risk. Screening is the single most powerful step, because removing polyps stops cancer before it starts. Healthy habits also help: eating more fibre, eating less processed meat, staying active, keeping a healthy weight, not smoking, and limiting alcohol.

Vaccines

There is no vaccine that prevents bowel cancer. Some vaccines protect against viruses linked to other cancers, but they do not affect bowel cancer risk.

Screening programmes

Screening programmes invite people who feel well to do a home stool test, usually every one to two years between about age 50 and 74. The exact ages and test types vary by country, so check your local programme. Some countries also offer a one-off camera test of the lower bowel around age 55. If you have a strong family history, an inherited condition, or long-term inflammatory bowel disease, you may be offered screening earlier or more often — ask your GP. If you are invited, please do take part: screening finds cancer earlier, when treatment is simpler and works best.

Complications

If left untreated

• Bowel cancer can grow through the bowel wall and spread to nearby lymph nodes or other organs, such as the liver or lungs
• A tumour can narrow or block the bowel, causing severe pain, vomiting, and a swollen tummy
• Ongoing slow bleeding can cause anaemia, leaving you tired and breathless
• Rarely, a blocked bowel can tear, which is a medical emergency
• Late-stage cancer is harder to treat, which is why screening and early checks matter so much

Long-term outlook

The outlook for bowel cancer is much better when it is found early. Cancers caught at an early stage can often be cured with surgery, and many people live a full, normal life afterwards. Screening is designed to catch problems at exactly that point. Treatment has improved a great deal in recent years, and even when cancer has spread, modern treatments can control it and help people live well for longer. Whatever your situation, your care team will be honest with you, plan treatment with you, and support you at every step.

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