Risks and benefits of colonoscopy

Overview

A colonoscopy is a test that lets a doctor look inside your large intestine (colon) using a long, flexible tube with a tiny camera. It helps find problems like polyps (small growths that can turn into cancer), inflammation, or bleeding. The test can also treat some issues, like removing polyps, during the same procedure.

Yes, colonoscopy is a common procedure, especially for people over 50 or those with a family history of bowel cancer. In the UK, the NHS offers bowel cancer screening using a home test kit, and many people with abnormal results go on to have a colonoscopy.

It is used for people of any age who have symptoms like blood in their stool, persistent changes in bowel habits, or unexplained weight loss. It is also recommended as a routine screening test for adults starting at age 50 (or earlier if you have higher risk due to family history or certain medical conditions).

Symptoms

Common symptoms

• Bleeding from your bottom or blood in your stool
• A lasting change in your bowel habits (diarrhoea, constipation, or feeling like you haven't finished a bowel movement)
• Unexplained weight loss
• Pain or a lump in your tummy

Symptoms in children

• Colonoscopy is less common in children, but it may be used if a child has chronic diarrhoea, bleeding, or suspected inflammatory bowel disease. Symptoms in children include tummy pain, blood in stool, and poor growth.

Symptoms in older adults

• In older adults, symptoms that may lead to a colonoscopy include blood in the stool, changes in bowel habits, or signs of anaemia (like tiredness and pale skin). Older adults are at higher risk of bowel cancer, so screening is important.

Causes

Main causes

• Colonoscopy is not a condition but a test. You might need it to find the cause of bowel symptoms like bleeding or changes in bowel habits.
• It is used to screen for bowel cancer, especially if you have a family history of the disease.
• It can also be done to check for polyps, inflammation (like in ulcerative colitis), or other abnormalities.

Risk factors

• Being over 50 years old
• A family history of bowel cancer or polyps
• Having a personal history of inflammatory bowel disease (like Crohn's or ulcerative colitis)
• Having certain genetic conditions (like Lynch syndrome)
• A diet high in red or processed meat, smoking, or being very overweight

When to see a doctor

See a doctor urgently if:

• If you have noticed blood in your stool, see your doctor within a few days.
• If you have a sudden change in bowel habits that lasts more than a few weeks, make an appointment.

Book a routine appointment if:

• If you are 50 or older and have not had a colonoscopy, talk to your doctor about screening.
• If you have a close family member (parent, sibling, child) who had bowel cancer, you may need to start screening earlier.

Diagnosis

A colonoscopy is both a diagnostic and sometimes a treatment procedure. Before the test, you will be given clear instructions on how to clean your bowel (using a special liquid). You will be given medicine to help you relax. Then the doctor passes the colonoscope through your bottom and into your colon. You might feel some pressure or mild discomfort, but not severe pain.

Tests that may be done

• Colonoscopy (the main test)
• Sometimes a CT scan (virtual colonoscopy) may be used if full colonoscopy is not possible
• Stool tests (like the faecal immunochemical test, or FIT) are often done first to check for hidden blood

What to expect at your appointment

On the day, you will be in a private room. A nurse will start a small tube in your arm to give sedation (medicine to help you relax). You will lie on your side. The test takes about half an hour. Afterward, you will rest until the sedation wears off. You will need someone to take you home and stay with you for 24 hours. Some people have mild bloating or cramping, but this passes quickly.

Treatment

During a colonoscopy, the doctor can treat some problems right away. For example, if they find polyps, they can remove them using a wire loop (polypectomy). This prevents the polyps from turning into cancer. They can also take small tissue samples (biopsies) to check for inflammation or cancer. If a narrowing or blockage is seen, they may be able to stretch it or place a small tube (stent) to keep it open – though this is less common.

Self-care at home

• After the test, rest for the remainder of the day.
• Drink plenty of fluids, but avoid alcohol for 24 hours.
• Eat light meals if you feel hungry; your bowel should return to normal within a day or two.

Medical treatments

If a colonoscopy finds a problem, further treatment depends on the cause. For polyps, removal during the test is usually enough. For inflammatory bowel disease, medications (like anti-inflammatories) may be prescribed. If cancer is found, you may need surgery, chemotherapy, or radiation therapy. Your healthcare team will guide you on the best plan.

When is surgery considered?

Surgery for bowel cancer may be needed if the tumour is large or has spread. The doctor will discuss options like removing part of the colon (colectomy). This is usually done after a full assessment and discussion with a surgeon.

Living with this condition

Most people feel back to normal within 24 hours after a colonoscopy. If you had sedation, do not drive, operate machinery, or make important decisions for that day. Follow any aftercare advice given by your doctor.

Lifestyle tips

• If you had polyps removed, you may need follow-up colonoscopies every few years to check for new polyps.
• A healthy diet with plenty of fibre and less red/processed meat can help reduce your risk of bowel cancer.
• If you have inflammatory bowel disease, ongoing care with a specialist is important.

Diet and exercise

After the test, you can return to your normal diet. In the long term, eating a balanced diet rich in fruits, vegetables, and whole grains, and getting regular exercise (like 30 minutes of walking most days) can support bowel health.

Mental health and emotional wellbeing

Waiting for test results or dealing with a bowel condition can be stressful. It is normal to feel worried. Talking to friends, family, or a counsellor can help. If you feel very anxious, let your healthcare team know – they can offer support or refer you to a mental health service.

Prevention

Colonoscopy itself is a preventive tool – it can find and remove polyps before they turn into cancer. While not all bowel cancers can be prevented, a healthy lifestyle and regular screening greatly reduce your risk.

Screening programmes

In the UK, the NHS offers bowel cancer screening to everyone aged 50 to 74 using a home test kit (FIT). If that shows blood, you will be offered a colonoscopy. If you have a family history, you may be offered screening earlier. Talk to your doctor about what is right for you.

Complications

If left untreated

• If polyps are not removed, they can grow and become cancerous over time.
• If symptoms like bleeding or changes in bowel habits are ignored, a serious condition like bowel cancer may be diagnosed at a later, harder-to-treat stage.

Long-term outlook

For the vast majority of people, colonoscopy is very safe and can save lives by catching problems early. The risk of a serious complication (like a tear in the bowel or excessive bleeding) is very low – less than 1 in 1,000. If you follow your doctor’s advice, the benefits of colonoscopy far outweigh the risks.

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