Ulcerative colitis (UC) causes inflammation and sores in the lining of the lower intestine (colon). A colonoscopy is a test that examines the inside of the colon. Doctors use this test to diagnose UC and determine its severity.

A colonoscopy is also a screening test for colorectal cancer — a cancer of the colon and rectum. Getting regular screenings is important for people who have UC. People with this disease are at higher risk of colorectal cancer.

What is colonoscopy?

Colonoscopy is one method that doctors use to diagnose UC. A colonoscope is a long, thin flexible tube with a camera at the end. The doctor uses it to view the inside of your colon and rectum.

You’ll prepare for this test a few days ahead of time by drinking a laxative that cleans out the inside of your colon. A clean colon is easier for your doctor to examine.

Before the test, you’ll get a sedative to relax you. You’ll also get medication to prevent discomfort.

During the test, you’ll lie on your side on a table. Your doctor will insert the scope through your anus.

Then your doctor will look for inflammation and sores inside your intestine. Any precancerous growths, called polyps, will be removed.

Your doctor may also remove a small piece of tissue and send it to a lab for testing. This is called a biopsy. It can help check for cancer or confirm your diagnosis.

Diagnosing ulcerative colitis

A colonoscopy looks for UC damage like swelling, redness, and sores in your intestine. It can show how severe the disease is, and how much of your colon it affects. Knowing the extent of your condition will help your doctor find the right treatment.

UC is divided into different conditions based on where it’s located in your colon.

  • Proctitis is only in the rectum. It’s the least severe form of UC.
  • Proctosigmoiditis is in the rectum and sigmoid colon — the lower part of the colon that’s closest to the rectum.
  • Left-sided colitis affects the area from the rectum to the splenic flexure — the bend in your colon near your spleen.
  • Pancolitis affects your whole colon.

Monitoring your treatment

UC treatments bring down inflammation and give your colon a chance to heal. Your doctor might do periodic colonoscopies to see whether the inflammation has gone down and your intestine lining has healed. These are signs that your treatment is working.

Screening for colorectal cancer

After you’ve lived with UC for many years, the inflammation can start to turn cells in your colon lining cancerous. People with UC are at higher risk of colorectal cancer than are people without the disease.

Your cancer risk begins to increase eight to 10 years after you’re diagnosed with — or start showing symptoms for — UC. The more severe your disease is and the more of your colon that’s inflamed, the higher your cancer risk becomes.

Overall, your risk is still low. Most people with UC will never get colon cancer. Still, it’s important to be watchful for cancer when you live with this disease.

Experts recommend that you start getting colonoscopy cancer screenings after you’ve had UC for eight years. If the test is negative, have repeat colonoscopies every one to two years. During the colonoscopy, your doctor should take biopsies.

Getting this test as often as recommended by your doctor can identify colorectal cancer early. The sooner you find cancer, the more likely treatment will be successful.