Ulcerative colitis and Crohn’s disease are both forms of inflammatory bowel disease. In both conditions, a person’s intestinal tract regularly becomes inflamed.

These bouts of inflammation occur as a result of the body’s immune system reacting inappropriately to the bacteria that live in a person’s gut.

However, there are some key differences involving where and how Crohn’s disease and ulcerative colitis affect a person’s bowels.

This article looks at the key differences between ulcerative colitis and Crohn’s disease. It details their symptoms, describes the diagnostic criteria and treatment options, and considers the outlook for people with these conditions.

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As one 2020 review explains, the main differences between ulcerative colitis and Crohn’s disease concern how they affect a person’s bowels and which parts of the bowels they affect.

Ulcerative colitis causes inflammation of the colonic mucosa, the innermost part of a person’s intestinal tract. By contrast, Crohn’s disease can affect any portion of the intestinal tract, including, but not limited to, the colonic mucosa.

Crohn’s disease typically affects a person’s colon, or large intestine, as well as their terminal ileum. The terminal ileum is the part of the intestinal tract where the small and large intestines meet.

Doctors can classify ulcerative colitis in different ways, depending on which bowel parts the condition affects:

  • Proctitis: Ulcerative colitis may affect the rectum.
  • Proctosigmoiditis: Ulcerative colitis can affect the sigmoid, which is the lower third of the large intestine.
  • Distal ulcerative colitis: Ulcerative colitis may affect other parts of the large intestine.
  • Pancolitis: Ulcerative colitis can affect the whole colon.

Ulcerative colitis and Crohn’s disease are so similar that, in at least 10% of people, it may initially be difficult to distinguish between these two conditions.

According to UCLA Health, ulcerative colitis and Crohn’s disease have the following similarities:

  • usually develop in adolescents or young adults
  • affect males and females equally
  • have similar symptoms
  • have unknown causes
  • can occur following exposure to similar risk factors, such as environmental, genetic, and immune system responses

Learn more about the similarities and differences between Crohn’s and ulcerative colitis here.

Although the symptoms of ulcerative colitis and Crohn’s disease can be very similar, some important differences do exist.

Ulcerative colitis

A 2020 review lists the following as common symptoms of ulcerative colitis:

These symptoms tend to worsen gradually. Many people with ulcerative colitis also find that their symptoms can improve for brief periods, though these will tend to worsen again later.

In other parts of the body

Other symptoms of ulcerative colitis are less common, arising for 10–30% of people who have this condition. These symptoms are extraintestinal, meaning that they do not affect the individual’s intestines. They include:

  • inflammation and infections affecting the eye
  • joint problems
  • swelling of the fat layer under a person’s skin
  • pyoderma gangrenosum, a rare inflammatory condition that causes ulcers to grow on the skin
  • axial arthropathies, or arthritis affecting the spine
  • ankylosing spondylitis, an inflammatory condition that affects a person’s spine

Learn more about the symptoms of ulcerative colitis here.

Crohn’s disease

Another 2020 review lists the following common symptoms of Crohn’s disease:

In other parts of the body

Like ulcerative colitis, Crohn’s disease can also lead to extraintestinal symptoms, including:

Learn more about the symptoms of Crohn’s disease here.

Comparison

The following symptoms are more common in Crohn’s disease than ulcerative colitis:

Strictures

Persistent inflammation keeps healing in the bowel, causing scar tissue to form. The bowel then narrows, which is called a stricture.

Fistulas

A fistula is a channel or passageway that connects one internal organ to the outside of the body or another organ.

The diagnostic procedures for ulcerative colitis and Crohn’s disease are somewhat different. However, since the conditions are similar, people presenting with symptoms of either condition may need to undergo testing for both.

Ulcerative colitis

According to researchers, several doctors use several methods to determine whether someone has ulcerative colitis:

  • Endoscopy: A doctor will insert a special tube into a person’s body. This tube has a camera at its end, which allows the doctor to observe the inside of a person’s intestinal tract. They can then see whether the intestinal tract carries signs of ulcerative colitis.
  • Biopsy: A biopsy involves the removal of a piece of tissue from a person’s body, which technicians will test for signs of a disease. Doctors must typically perform several biopsies to diagnose ulcerative colitis.
  • Stool examination: Stool examinations are also an important diagnostic tool. These can help doctors test for various colonic infections, which can have similar symptoms to ulcerative colitis.

Crohn’s disease

The following are diagnostic methods for Crohn’s disease:

  • Endoscopy: As with ulcerative colitis, doctors use endoscopies to observe a person’s inner intestinal tract.
  • Stool examination: Stool examinations help doctors rule out infectious diseases, such as ulcerative colitis.
  • Blood tests: Blood tests can help doctors distinguish Crohn’s disease from ulcerative colitis. They can also help doctors detect fatty liver disease and anemia, which Crohn’s disease can cause.
  • Scans: Doctors may also use CT scans or MRI scans to check for abscesses and fistulas.

Ulcerative colitis and Crohn’s disease have similar treatment methods.

Ulcerative colitis

Doctors treat ulcerative colitis with different medications, which may vary with the severity of the disease. These include:

  • sulfasalazine
  • 5-aminosalicylates
  • glucocorticoids

In later stages, or if medications are not working, doctors may recommend a colectomy. This is a surgical procedure to remove a person’s colon, or parts of it.

Learn about treatment for ulcerative colitis here.

Crohn’s disease

With Crohn’s disease, doctors also have a variety of treatment options to choose from:

  • medication that reduces inflammation
  • medication that stops inflammation from arising in the first place
  • surgical procedures to remove parts of the intestinal tract
  • mental healthcare, to help people cope with their symptoms

Learn about treatment for Crohn’s disease here.

Both ulcerative colitis and Crohn’s disease are lifelong conditions. Although treatment can help people manage their symptoms, there is no cure for either condition.

Researchers note that overall mortality for people with ulcerative colitis is identical to that of the general population. Nonetheless, people with ulcerative colitis are at an increased risk of developing colon cancer.

By comparison, researchers also point out that people with Crohn’s disease have a slightly reduced life expectancy in comparison with the general population.

Many people with Crohn’s disease develop depression as a result of their symptoms. If a person experiences stress as a result of an ulcerative colitis or Crohn’s diagnosis, they may benefit from exploring mental health resources.

Learn about mental health resources and how to access them here.

Crohn’s disease and ulcerative colitis are serious conditions that can have a sizable effect on a person’s quality of life.

These conditions affect different parts of the bowels, but they cause some of the same symptoms, and doctors treat them in a similar way.

Anyone with signs of either condition should promptly seek the advice of a doctor, as an early diagnosis can make treatment more effective.