By Manda Barger
Illustration of human intestine, the difference between UC and Crohns

Medically reviewed by Jenny Blair, MD

When you’re diagnosed with inflammatory bowel disease (IBD), it can be a time of uncertainty. What does it mean for your health? What about your lifestyle? What are your treatment options?

There can also be confusion over which IBD you have. Since their symptoms are similar, patients—and even doctors—can mix up the two main types, Crohn’s disease (CD) and ulcerative colitis (UC). When my symptoms began in 2013, my local gastroenterologist struggled to pick a diagnosis, but ultimately chose UC.

I sought a second medical opinion, and it was Dr. Robin Dalal who properly diagnosed me with Crohn’s in 2018. She is an assistant professor of medicine at Vanderbilt University Medical Center in Nashville, Tennessee, and serves patients like me at the hospital’s IBD clinic. There, she says they are typically able to diagnose based on disease location—but not always. With some patients, especially if it’s just inflammation in the colon, sometimes we really can’t tell, Dr. Dalal explains.

Is It UC or CD?

Fortunately, there are other ways to tell. Though UC and CD are alike in some ways, they also have distinct differences—like how they affect the gastrointestinal (GI) tract.

  • UC affects only the colon and rectum, while CD can affect any part of the GI tract, from the mouth to the anus.
  • When you have CD, damage to the intestinal wall is patchy and interspersed with spots of healthy tissue. These areas of damage are called “skip lesions.” If it’s UC, the damage occurs along a continuous area.
  • “In UC, the inflammation is only on the mucosal [first] layer of the colon,” says Dr. Dalal. “In Crohn’s disease, the inflammation is what we call ‘transmural inflammation,’ and that means a kind of deeper inflammation.”

Symptoms like abdominal pain and bloody stool are common to both diseases, but CD patients may also discover sores in their mouth or experience symptoms arising from their esophagus or stomach due to inflammation beyond the bowel.

People with UC or CD can have similar complications, as well, though some occur more frequently depending on the disease. Dr. Dalal says complications she sees primarily in CD include:

  • Abscesses: pockets of pus that may need surgical drainage
  • Fistulas: abnormal tunnels from the GI tract to other organs or the skin
  • Bowel obstruction: blockages that prevent food or gas from moving through the colon, risking rupture

The complications she sees more frequently in UC include:

  • Perforated colon: a hole that develops in the colon
  • Toxic megacolon: an infection that causes the colon to swell, risking a rupture
  • Primary sclerosing cholangitis: a liver disease in which bile ducts become damaged, often leading to liver failure

How Treatment Differs Depending on Diagnosis

Dr. Dalal says while some aspects of treatment can be similar for CD and UC, “there are a few medications only approved for one or the other.” For example, certolizumab (Cimzia) and ustekinumab (Stelara) are biologic drugs used for CD therapy, while tofacitinib (Xeljanz) is used for UC patients.

No matter what form of IBD a patient has, each symptom, complication and treatment can vary. Dr. Dalal warns against getting hung up on labels. “We try to take the individual patient, what their disease is like, what their disease is doing, and what their preference is, and we come up with a treatment plan together,” she says.

Jenny Blair is a writer and journalist covering science, medicine, and the humanities. She earned her MD at Yale University, then completed a residency in emergency medicine at the University of Chicago. After several years in practice, she transitioned to working with words and ideas full-time. Jenny has contributed to Discover, New Scientist, Washington Spectator, and Medtech Insight, among other publications. She lives in New York City.

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