An Overview of Crohn's Disease

Crohn's disease is a chronic, incurable, immune-mediated disease that can cause inflammation anywhere along the digestive tract from the mouth to the anus. Along with ulcerative colitis, Crohn's disease is one of the major forms of inflammatory bowel disease (IBD). Crohn's disease commonly involves all layers of the intestinal wall, causing deep ulcers. People with Crohn's disease are typically cared for by a gastroenterologist (a specialist in digestive disease) and sometimes a colorectal surgeon (a surgeon that specializes in the digestive tract).

While a diagnosis of Crohn's disease is life-altering and the disease will need to be managed, the future for people with IBD is bright. There are more choices for medical treatments than ever before, and new therapies are being studied in order to be brought to patients. The exact cause and cure are still being studied, and there's more research currently being done on IBD than ever before.

The Most Important Things to Know About Crohn's Disease

Forms of Crohn's Disease

Different terms are used to describe Crohn's disease, depending on what part of the digestive tract is affected.

Not every case of Crohn's disease will fall neatly into a category, but these are the forms that are most frequently described and may be used by physicians:

  • Ileocolitis. The most common form of Crohn's disease which affects the ileum (lower end of the small intestine) and the colon (large intestine).
  • Ileitis. Also known as fistulizing or perforating Crohn's disease, this type affects only the ileum.
  • Gastroduodenal Crohn's disease. This form affects the stomach and duodenum (first part of the small intestine).
  • Jejunoileitis. Crohn's disease characterized by intermittent areas of inflammation in the jejunum (middle section of the small intestine).
  • Crohn's colitis. Sometimes called granulomatous colitis, this form affects only the colon, and shouldn't be confused with ulcerative colitis, which is a different form of IBD. Crohn's colitis is a form of Crohn's disease, and it does not mean that a person has both Crohn's disease and ulcerative colitis.

Symptoms of Crohn's Disease

Crohn's disease causes various signs and symptoms, some of them in the digestive tract and some of them outside the digestive system.

The symptoms of Crohn's disease can include:

Possible Causes of Crohn's Disease

There are theories about the cause of Crohn's disease and IBD in general, but IBD is currently classified as an idiopathic disease (a disease with unknown cause). Crohn's disease does tend to run in families, although most people with IBD don't have a family history of the disease.

One theory about the cause of IBD is that it could be an allergic or immune response, largely based on the fact that IBD is an immune-mediated disease. Environmental factors have also been implicated, but there is no consensus in the medical community as to exactly which factors might influence the onset of IBD. Another potential cause could involve the microorganisms (the bacteria) that live in the digestive tract, called the gut or the intestinal microbiome. It's not understood yet how changes in the microbiome can affect the development of Crohn's disease, but it is known that people with Crohn's disease tend to have fewer types of bacteria in their digestive tract than people without digestive disease.

The true cause of IBD could still be any combination of these or even something that is yet undiscovered.

How Crohn's Disease Is Diagnosed

A physician might first suspect Crohn's disease based on a history of symptoms such as pain, diarrhea, unintended weight loss, and blood in the stool. The two tests used to make a diagnosis of Crohn's disease are:

  • Colonoscopy. This test is used to look inside the colon to see if inflammation is present.
  • Sigmoidoscopy. A look inside the colon, much like a colonoscopy, but that only goes as far as the last section of the large intestine

Other tests may not used in diagnosis, but could be done to monitor Crohn's disease activity or complications include:

  • Barium enema. This test is a type of x-ray that uses a contrast in order to better see the structures in the lower digestive tract.
  • Blood tests. Blood tests are also commonly done to provide helpful information about the status of IBD, especially red blood cell and white blood cell counts. Other blood tests can measure electrolyte levels, such as sodium and potassium, to determine if they are depleted from persistent diarrhea.
  • Upper endoscopy. When there is the potential for disease in the upper digestive tract (such as the esophagus, throat, or small intestine), this test may be helpful.
  • Upper gastrointestinal series. Another form of x-ray that uses contrast and is used for the upper digestive tract.
  • X-rays. A quick and easy test that doesn't give a lot of information but is still sometimes used.

How Crohn's Disease Is Treated

Both medications and surgery are used to treat Crohn's disease. With the variety of treatments available, it's important to work closely with a gastroenterologist to determine the best course of action.

Medication. A variety of medications may be used to treat Crohn's disease. Medications typically fall into two categories: Maintenance drugs, which are taken continuously to prevent flare-ups, and quicker-acting drugs, which are taken to stop a flare-up.

Medications used to treat Crohn's disease include: Azulfidine (sulfasalazine); Asacol and Pentasa (mesalamine); Imuran (azathioprine); Purinethol (6-MP, mercaptopurine); cyclosporine; Rheumatrex (methotrexate); Remicade (infliximab); Humira (adalimumab); Entyvio (Vedolizumab); Cimzia (certolizumab pegol); and corticosteroids, such as prednisone and Entocort EC (budesonide).

Surgery. Surgery is also used as a treatment for Crohn's disease. Approximately 70 percent of people with Crohn's disease will have surgery in the first 10 years after diagnosis. Of those, half will have more surgery in the next three to four years. Resection, where a diseased section of intestine is removed, is the most common type of surgery. Surgery is not a cure for Crohn's disease.

Risk of Gastrointestinal Cancers

For people with Crohn's disease, there are several factors that seem to affect the risk of developing colorectal cancer. These risks include:

  • young age at diagnosis
  • 8 to 10 years of active disease with inflammation
  • having strictures (a narrowing of the intestine)
  • history of the liver disease, primary sclerosing cholangitis

Physicians may recommend a screening colonoscopy every two to three years after eight to 10 years of Crohn's disease, and every one to two years after 20 years of Crohn's disease. Some people with Crohn's disease may require colonoscopy at regular intervals to monitor their disease, and screening for cancer may be done at the same time.

Related Conditions

Extra-intestinal. There can be complications associated with Crohn's disease, and those that occur outside the colon are called extra-intestinal complications. Extra-intestinal complications include arthritis, delayed growth in children, eye diseases, gallstones, skin conditions, mouth ulcers, and a worsening of symptoms during menstruation. Many of these complications will follow the course of the Crohn's disease, and may get worse before and during a flare and improve when the Crohn's disease is in remission.

Intestinal. Some of the potential local (intestinal) complications of Crohn's disease include abscesses, bowel obstruction, bowel perforation, colorectal cancer, fissures, fistulas, and toxic megacolon.

Smoking and Crohn's Disease

People who smoke cigarettes, or who have smoked in the past, have a higher risk of developing Crohn's disease. Relapses (flare-ups), repeat surgeries, and aggressive immunosuppressive treatment are more common in patients with Crohn's disease who also smoke. People with Crohn's disease are strongly encouraged to quit smoking.


A healthy pregnancy and baby are both possible for women who have Crohn's disease. How Crohn's disease will respond during pregnancy is roughly split into thirds: some women do better, some stay the same, and some worsen. The most important thing is to get into remission before a pregnancy, or getting there during pregnancy, to ensure that Mom and baby continue to do well. Unfortunately, when Crohn's disease is flaring at the time the baby is conceived or during the course of the pregnancy, the risk of miscarriage and premature birth is higher.


With proper medical care, the prognosis for most people with Crohn's disease is good. Most people with Crohn's disease are able to lead long, productive lives. New medications and research into the causes of IBD continue to increase the quality of life for people with IBD.

A Word From Verywell

A diagnosis of Crohn's disease comes with a steep learning curve. The gastroenterologist and their staff are going to be critical in ensuring that a good quality of life is preserved. Most IBD patients have close relationships with their gastroenterologists. It's also important for people with IBD to develop a support network amongst their family and friends who can be advocates. Living well with Crohn's disease is not out of reach by keeping regular doctor's appointments, following a treatment plan, and learning as much as possible about the disease.


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Nørgård B, Hundborg HH, Jacobsen BA, Nielsen GL, Fonager K. Disease Activity in Pregnant Women With Crohn's Disease and Birth Outcomes: A Regional Danish Cohort Study. Am J Gastroenterol. 2007 Sept;102:1947-1954.

Veloso FT. Clinical predictors of Crohn's disease course. Eur J Gastroenterol Hepatol. 2016 Jul 7. [Epub ahead of print]

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