Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD). It is a chronic condition that causes inflammation and sores to form in the inner lining of the colon.

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UC affects nearly 1 million people in the United States, and it most commonly develops in people ages 15–30 and 50–70 years.

Medical professionals use a type of exam known as endoscopy to diagnose UC. They also use endoscopy to learn how well treatment is working and to check for signs of colorectal cancer, which is more common in people with UC.

Read on to learn how healthcare professionals use endoscopy to diagnose and manage UC.

Endoscopy is a type of exam that allows medical professionals to examine the inside of the gastrointestinal (GI) tract. They use a thin tube known as a scope, which has a light and camera on one end.

There are several types of endoscopy to diagnose or monitor UC, including:

  • Sigmoidoscopy: During this procedure, a healthcare professional inserts a scope through the anus to examine the rectum and left colon.
  • Colonoscopy: A healthcare professional inserts a scope through the anus to examine the rectum and full length of the colon.
  • Chromoendoscopy: A healthcare professional sprays dye on the inner lining of the colon to make any irregularities more visible during an endoscopy.

Healthcare professionals may also perform biopsies during endoscopy by taking tissue samples to analyze under a microscope.

To diagnose UC, doctors start by assessing a person’s medical history, including their symptoms.

“Typical symptoms of ulcerative colitis include blood in the stool, diarrhea, weight loss, and abdominal pain,” Dr. Kerri L. Glassner, DO, told Medical News Today.

Dr. Glassner is a gastroenterologist at Houston Methodist Hospital and an assistant professor of clinical medicine at Weill Cornell Medical College and Houston Methodist Academic Institute in Texas.

If a person has symptoms of UC, a doctor will order blood and stool tests to check for signs of inflammation and infection. Many GI infections can cause symptoms similar to those of UC.

If tests are negative for infections, the doctor will refer the person to a GI specialist for an endoscopy.

The American College of Gastroenterology (ACG) recommends colonoscopy with tissue biopsies to diagnose UC. This type of endoscopy allows the specialist to understand whether a person has UC, how severe it is, and the area affected.

It also helps them rule out other conditions that cause similar symptoms, such as Crohn’s disease and colorectal cancer.

GI specialists use endoscopy not only to diagnose UC but also to learn how the condition is responding to treatment. This can help them determine whether a person needs changes to their treatment plan.

The goal of treatment is to bring UC into remission. This happens when someone with UC has few to no symptoms, and the lining of their colon has healed.

“Once a patient [has] improved, a colonoscopy is often repeated 6 to 12 months later to make sure that the lining of the colon has healed with treatment. Then, colonoscopy may be repeated at varying intervals based on patient symptoms,” said Dr. Jeffry A. Katz, MD, a professor of medicine at Case Western Reserve University School of Medicine and the medical director of IBD at University Hospitals Cleveland Medical Center in Ohio.

In a 2017 review, researchers noted that when the lining of the colon heals, people with UC are more likely to stay in remission. They are also less likely to need surgery to remove the colon.

A 2020 paper notes it is possible for someone with UC to have few or no symptoms while their colon still has inflammation.

Blood test results are also imperfect markers of disease activity in UC. For example, the ACG reports that up to one-quarter of people with active UC have typical levels of C-reactive protein in their blood. This protein is a marker of inflammation.

According to the ACG, studies suggest that certain fecal markers in stool may offer an alternative to colonoscopy for tracking disease activity. However, more research is needed to determine whether these markers are viable.

Healthcare professionals also use endoscopy to screen for colorectal cancer and dysplasia, which are abnormal cells that may develop into cancer.

Colorectal cancer is the second leading cause of cancer-related deaths in the United States. Removing dysplasia can help prevent colorectal cancer. When cancer does develop, early diagnosis and treatment are important for improving survival.

According to a 2022 review, people with UC are more likely than average to develop colorectal cancer.

“The risk is influenced by the extent of disease, duration of disease, severity of disease, amount of healing on treatment, and whether the patient has a family history of colon cancer, smokes cigarettes, or has an associated condition called primary sclerosing cholangitis,” said Dr. Katz.

If an individual has UC that extends beyond their rectum, the ACG recommends colonoscopies to check for abnormal cells in the lining of the colon every 1–3 years, starting 8 years after a person receives their diagnosis.

During surveillance colonoscopies, medical professionals look for irregularities in the colon lining and remove tissue samples for analysis.

If they find abnormal cell growth, they may be able to remove the affected area. However, if they cannot completely remove these cells, they may recommend surgery to remove the colon.

“A finding of dysplasia on a surveillance colonoscopy often leads to a recommendation to have the colon surgically removed,” said Dr. Katz. “The idea is to save a life before cancer develops.”

A 2018 review of research links colorectal cancer surveillance in people with IBD and 64% reduced risk of colorectal cancer-related death.

To prepare for endoscopy, people typically need to adjust their diet for several days beforehand. This reduces the amount of undigested food in their colon.

“Patients are asked to follow a low residue diet for 2 to 3 days prior to the procedure, limiting their intake of roughage in the form of fruits, vegetable, and nuts,” Dr. Katz told MNT. “The day prior to the examination,” he continued, “patients follow a clear liquid diet.”

Doctors also ask people to complete a bowel preparation before endoscopy. This involves taking medication that causes frequent and loose bowel movements.

“Patients are instructed to consume one of several available preparations that cause diarrhea so that the colon is cleansed of stool before the examination,” said Dr. Katz.

“This preparation is usually split, with roughly half consumed the evening prior to the colonoscopy and the other half consumed 3 to 4 hours prior to the procedure,” he added.

When it is time for the exam, the person will receive a sedative, so they are semiconscious during the procedure.

Authors of a 2019 review pool the results of past studies on endoscopy to screen for colorectal cancer worldwide. They note that the risk of serious side effects is low.

A 2023 review of research finds severe bleeding in 8 in 100,000 sigmoidoscopies and 68 in 100,000 once-only colonoscopies.

Severe colon perforation occurs in 53 in 100,000 once-only colonoscopies. There are no perforations in 100,000 sigmoidoscopies. Colon perforation is when something creates a hole in the colon.

Some studies note that people with IBD are more likely than average to experience colon perforation from colonoscopy. However, other studies do not show increased risk in people with IBD.

Other rare but potentially serious risks of colonoscopy include reactions to sedatives. These reactions may cause breathing or heart problems.

A 2023 review notes that 1 in 10 people experience less severe side effects during or after endoscopy. Symptoms of discomfort include:

  • pain in the abdominal area
  • cramping
  • bloating
  • nausea

Early and accurate diagnosis of UC can help people get the treatment they need to bring the condition into remission. This helps limit symptoms and improves colon health.

Medical professionals also use endoscopy to learn how a person’s body is responding to treatment for UC. If the lining of the person’s colon has not healed with treatment, a doctor may adjust their treatment plan.

After a person has been living with UC for several years, a doctor may order colonoscopies to check for signs of colorectal cancer or abnormal cells that can develop into cancer.

A person can contact a doctor to learn more about the potential benefits and risks of endoscopy.