Indeterminate Colitis

Reviewed by: HU Medical Review Board | Last reviewed: February 2024 | Last updated: February 2024

Indeterminate colitis is a type of inflammatory bowel disease (IBD). Doctors use the term “indeterminate colitis” when you have signs of both Crohn’s disease and ulcerative colitis (UC). This means that it is not clear which type of IBD you have. Indeterminate colitis also may be called inflammatory bowel disease unclassified (IBDU).1,2

Some people diagnosed with indeterminate colitis get diagnosed with Crohn’s or UC later. The uncertainty about the condition can be frustrating, and deciding on treatment options can be hard. Talk to your doctor about ways to manage symptoms.1,2

What is indeterminate colitis?

When they are first diagnosed, 10 to 15 percent of people with IBD are diagnosed with indeterminate colitis. The condition looks like both Crohn’s disease and UC. For example, ulcers in the large intestine are a common sign of UC. But some people have ulcers deeper than expected for UC without any other signs of Crohn’s. This may lead to a diagnosis of indeterminate colitis.1,2

For some people, indeterminate colitis is an early form of Crohn’s or UC. Eventually, they will be diagnosed with one or the other. But some experts argue that it is a separate type of IBD. This is because the frequency of adults with indeterminate colitis has not changed despite better diagnostic methods.2

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What causes indeterminate colitis?

Experts do not yet know what causes indeterminate colitis. In fact, the exact causes of IBD are unknown. For example, diet and stress do not cause IBD, but they can make the condition worse.3

One possible cause is abnormal immune system activity. When the immune system attacks cells in the digestive tract, it can lead to inflammation in the gut.3

IBD also may have genetic causes. It is more common in people who have family members with IBD. Like other types of IBD, indeterminate colitis is more common in women and children. Cigarette smoking and taking nonsteroidal anti-inflammatory drugs (NSAIDs) may increase your risk for IBD.3

How is indeterminate colitis diagnosed?

Indeterminate colitis is diagnosed when your doctor cannot determine whether you have Crohn’s or UC. Doctors use certain tests to diagnose IBD, including:1,2

  • Blood tests
  • Stool tests
  • Upper endoscopy or colonoscopy
  • Biopsy
  • Imaging tests, such as MRI and CT scans

If these tests show features of both Crohn’s and UC, your doctor may diagnose you with indeterminate colitis. Doctors are still debating how to classify the condition. The uncertainty makes it hard to diagnose and treat.1,2

Children are twice as likely to be diagnosed with indeterminate colitis as adults. About 80 percent of children with indeterminate colitis are diagnosed with Crohn’s disease or UC later in life.1,2

In these cases, indeterminate colitis may have been an early stage of IBD or a misdiagnosis. But some people maintain an indeterminate colitis diagnosis for their whole lives.1,2

What are the symptoms of indeterminate colitis?

Symptoms of indeterminate colitis may differ from person to person. They can range from mild to severe. Symptoms depend on where inflammation occurs. Many symptoms are caused by trouble absorbing nutrients from food.1

Common of symptoms indeterminate colitis include:1,2

  • Abdominal pain and cramping
  • Persistent diarrhea
  • Blood in the stool
  • Bleeding from the rectum
  • Unexpected or unintended weight loss
  • Reduced appetite
  • Fever
  • Fatigue

Symptoms can vary and affect many parts of the body. Talk to your doctor about any symptoms you notice.1

What are the treatment options for indeterminate colitis?

Initial treatment is similar to that for other types of IBD. Most often, doctors tend to follow the treatment guidelines for UC. Treatment options include:4,5

  • Biologic therapy
  • Corticosteroids
  • Anti-inflammatory drugs
  • Immune system-suppressing drugs
  • Antibiotic drugs
  • Ileal pouch-anal anastomosis (IPAA) surgery

There is not enough evidence to know the best treatment for indeterminate colitis. Many treatments improve symptoms of both UC and Crohn’s. But some treatments for 1 type of IBD may be harmful to people with the other type of IBD.4,5

For example, IPAA surgery is an effective treatment for UC. But some people with indeterminate colitis who have the surgery get diagnosed with Crohn’s later. This may be why people with indeterminate colitis have more post-surgery complications than people with UC.4,5