CT colonography

Overview

CT colonography (also called virtual colonoscopy) is a special type of CT scan that takes detailed pictures of your large bowel (colon) and rectum. It uses X-rays and a computer to create 3D images, so doctors can look for polyps (small growths) or signs of cancer without needing a tube inserted into your bowel.

CT colonography is becoming more common as a screening test for bowel cancer, especially for people who cannot have a standard colonoscopy or prefer a less invasive option.

It is mainly used for adults aged 50 and over, or younger people with a higher risk of bowel cancer (such as a family history). Your doctor will decide if it is right for you.

Symptoms

Common symptoms

• Blood in your stool (poop) or bleeding from the rectum
• A persistent change in bowel habits — such as diarrhea or constipation lasting more than a few weeks
• Unexplained weight loss
• Feeling like you haven't fully emptied your bowel after a movement
• Pain or a lump in your abdomen (tummy)

Symptoms in children

• CT colonography is very rarely used in children. If a child has symptoms like blood in stool or severe abdominal pain, a doctor will usually recommend other tests first.

Symptoms in older adults

• CT colonography may be a good option for older adults who cannot undergo a full colonoscopy due to other health problems or risks from sedation.
• Bowel preparation (cleaning the bowel) can be harder for older adults, so the doctor will provide specific instructions to avoid dehydration.

Causes

Main causes

• Polyps can grow in the lining of the bowel for reasons that are not fully understood. Some polyps may become cancerous over time.

Risk factors

• Age 50 or older
• A family history of bowel cancer or polyps
• A personal history of inflammatory bowel disease (like Crohn's disease or ulcerative colitis)
• A diet high in red or processed meat
• Being overweight or obese
• Smoking
• Drinking alcohol in large amounts

When to see a doctor

See a doctor urgently if:

• If you have severe abdominal pain, heavy rectal bleeding, or feel very unwell, call your local emergency number or go to the nearest emergency department right away.

Book a routine appointment if:

• Talk to your doctor about bowel cancer screening if you are over 50, or earlier if you have a strong family history.
• See your doctor if you notice blood in your stool, a lasting change in bowel habits, or unexplained weight loss.

Diagnosis

CT colonography is a scan that helps diagnose polyps, cancer, or other problems in the large bowel. It is not a procedure to treat anything — it is a way of looking for issues.

Tests that may be done

• CT colonography (virtual colonoscopy)
• Standard colonoscopy (using a camera on a flexible tube)
• Fecal immunochemical test (FIT) — checks for hidden blood in stool
• Flexible sigmoidoscopy — looks at the lower part of the bowel only

What to expect at your appointment

Before the scan, you will be asked to follow a clear-liquid diet for about 24 hours and take laxatives to clean out your bowel. On the day of the scan, a small tube may be placed in your rectum to gently inflate your bowel with air. You will lie on a table that slides through a ring-shaped scanner. The scan itself takes only a few minutes and is not painful. You will be awake and can go home straight after.

Treatment

Treatment depends on what the CT colonography finds. If no polyps are seen, you may just need follow-up screening in a few years. If polyps are found, they are usually removed during a standard colonoscopy to prevent them from turning into cancer. If cancer is found, treatment may include surgery, chemotherapy, or radiotherapy — your specialist will discuss the best plan for you.

Self-care at home

• Follow your doctor's advice about bowel preparation exactly — this helps get clear images.
• Drink plenty of clear fluids on the day before the scan to avoid dehydration.
• After the scan, you can eat and drink normally unless your doctor says otherwise.

Medical treatments

If the CT colonography shows a polyp, your doctor may arrange a colonoscopy to remove it. For cancer, treatments include surgery to remove the affected part of the bowel, and sometimes chemotherapy or radiotherapy. Your healthcare team will explain all options and help you decide what is right for you.

When is surgery considered?

Surgery is commonly needed if cancer is found. The surgeon removes the section of bowel containing the cancer and joins the healthy ends back together. In some cases, a temporary or permanent colostomy (stoma) may be needed.

Living with this condition

After a CT colonography that finds no problems, you can return to your normal routine straight away. If polyps are removed during a later colonoscopy, you may need to take it easy for a day. If you are diagnosed with bowel cancer, you will have a treatment plan and support from a specialist team.

Lifestyle tips

• Eat a balanced diet rich in fruits, vegetables, and whole grains.
• Limit red and processed meats.
• Stay physically active — aim for at least 150 minutes of moderate activity each week.
• Maintain a healthy weight.
• Avoid smoking and limit alcohol.

Diet and exercise

A high‑fibre diet can help keep your bowel healthy after treatment. Gentle exercise, like walking, can aid recovery and improve your mood. Always check with your doctor before starting a new exercise program, especially after surgery.

Mental health and emotional wellbeing

Having a bowel cancer screening or diagnosis can cause worry, anxiety, or low mood. It is normal to feel this way. Talk to your doctor or a counsellor about how you are feeling. Many hospitals have support services for people going through treatment.

Prevention

You cannot always prevent bowel cancer, but healthy lifestyle choices and regular screening can lower your risk. Detecting and removing polyps early through screening tests like CT colonography can prevent them from becoming cancer.

Screening programmes

If you are aged 50 to 74, many countries offer bowel cancer screening every two years. CT colonography is one of the screening options. Talk to your doctor about which test is best for you.

Complications

If left untreated

• Polyps that are not removed may grow and turn into cancer over time.
• Untreated bowel cancer can spread to other parts of the body (metastasis), making it harder to treat.

Long-term outlook

When bowel cancer is found early, the chances of successful treatment are very high. Even for more advanced cancers, treatments have improved a lot in recent years. Many people live well after treatment, and follow-up care helps keep you healthy.

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