What Is Crohn’s Disease?

You’re not alone if you have questions about Crohn’s disease, the chronic inflammatory bowel disease that causes cramps, diarrhea, gas and many other symptoms and potential complications. Cases of Crohn’s appear to be increasing in the U.S., with an estimated 1.5 million cases reported in 2015 (the most recent statistics listed by the Centers for Disease Control and Prevention), compared to a million diagnoses in 1999. “There’s been a rising incidence of Crohn’s disease over the past 15 to 20 years, and it may go beyond greater awareness leading to more diagnoses; there may be more disease out there,” says Dr. Wilson Jackson, a gastroenterologist based in Harrisburg, Pennsylvania.

Understanding Crohn’s

Crohn’s disease is characterized by flare-ups of inflammation — swelling or sores caused by an immune system attack — scattered along the walls of the gastrointestinal tract. The GI tract includes the mouth, esophagus, stomach, small and large intestines, rectum and anus.

“Crohn’s disease has transmural inflammation, meaning it affects all layers of the the GI tract walls, most commonly in the small intestines and colon,” explains Dr. Daniel Bushyhead, a gastroenterologist with Houston Methodist Hospital.

One way Crohn’s disease is classified is based on how the disease behaves. For example, there’s:

Fistulizing Crohn’s disease. This involves little tunnels or fistulas that link the bowel to other organs or vessels, which can cause the leakage of feces (within the body), infection and pain.

Stricturing Crohn’s disease. This is a type of Crohn’s that causes strictures (narrowed areas) in the intestines that need to be removed.

Inflammatory Crohn’s disease. This type includes inflamed segments of the GI tract but no signs of fistulas or strictures.

Another way Crohn’s disease is categorized is based on the location of inflammation. These types include:

Ileocolitis, which strikes where the small and large intestines meet. It’s the most common type of Crohn’s disease.

Ileitis, which involves the last part of the small intestine (the ileum).

Gastroduodenal Crohn’s disease, which involves the stomach and first part of the small intestine (the duodenum).

Jejunoileitis, which involves the top half of the small intestine (the jejunum).

Crohn’s (granulomatous) colitis, which involves only the large intestine.

[SEE: Which Doctor Should I See for Digestive Issues?]

Symptoms and Complications

People with Crohn’s disease experience flare-ups or bouts of symptoms. These can include:

Persistent diarrhea.

— Abdominal pain.

— Weight loss or, in children, poor growth.

Bloody stool.

— Pain and inflammation around the anus.

— Fever.


— Sores in the mouth.

— Inflammation of the skin, eyes, joints, liver or bile ducts.

The particular combination of symptoms you have will depend on the type of Crohn’s affecting you.

For example:

— People with Ileitis are likely to experience diarrhea, pain in the middle or lower right abdomen and weight loss.

— People with Crohn’s (granulomatous) colitis experience diarrhea, rectal bleeding and ulcers near the anus.

— People with gastroduodenal Crohn’s disease experience nausea, vomiting and weight loss.

Crohn’s disease can also lead to potentially life-threatening complications, such as infections, bowel narrowing or perforation and colorectal cancer. If untreated, those complications can play a role in shortening life expectancy.

Crohn’s Disease Causes

Doctors can’t say for sure what causes Crohn’s disease. They believe it’s probably a number of factors that flip an “on” switch telling the immune system to attack, which causes inflammation. Possible contributors might include:

Family history. Crohn’s disease often runs in families. More than 170 genes are associated with the condition. “A person probably has a certain gene that predisposes them to the disease. Then something flips the switch,” Jackson says.

Smoking. Smoking is considered a major risk factor for developing Crohn’s disease. “Smoking breaks down the mucus layer in the intestinal tract,” Jackson explains.

Imbalanced gut bacteria. “We all have trillions of microbes — viruses, bacteria and fungi — that help maintain the health of the GI tract and prevent other pathogenic or disease-causing microbes from wreaking havoc in our bodies. If those normal microbes are not there or not performing their function to protect the GI system, it can lead to a disruption in normal defense mechanisms, and that can lead to inflammation, which is the cardinal feature of inflammatory bowel disease,” Bushyhead says.

Diet. “Diet is important in determining the composition of microbes in the gut and maintaining them, and some theories suggest a Western diet (such as processed foods, high amounts of sugar and lots of red meat) contributes to Crohn’s disease,” Bushyhead says.

Chinks in the armor. A tight barrier of cells in the intestinal tract keeps microbes in the gut. If it’s compromised, bacteria in the intestinal tract can gain entry to the underlying tissue that’s normally sterile or to other parts of the body.

[Read: A Patient’s Guide to Digestive Diseases.]


Diagnosing Crohn’s disease starts with a visit to your primary care doctor, who can rule out certain causes of your symptoms and determine if you need further evaluation by a gastroenterologist.

If a gastroenterologist suspects you have Crohn’s disease, it may take several tests to confirm it. These can include:

Blood work. Your doctor will want to look for signs of low iron or anemia (a lack of red blood cells), since you can lose blood with the disease.

Stool tests. These tests check stool for pathogens that can cause diarrhea, such as giardia. “We’ll also check calprotectin levels. High levels indicate inflammation,” Jackson explains.

An endoscopy. An endoscopy is a procedure that allows a doctor to look inside the body with a thin, flexible, lighted tube that has a camera on the end. In a colonoscopy, a tube is inserted through the anus and into the colon. In an upper endoscopy, a tube is inserted through the mouth and esophagus and into the stomach and first part of the small intestine.

To get more information about hard-to-reach parts of the digestive tract, your doctor might order:

— Imaging tests, such as computed tomography enterography or magnetic resonance enterography.

— Capsule endoscopy, which involves swallowing a pill-sized wireless camera that sends pictures to a computer. The camera later exits the body in bowel movements.

[See: Questions Doctors Wish Their Patients Would Ask.]


Treating Crohn’s disease focuses on managing symptoms, healing inflammation and preventing complications. Treatment approaches may include:

Medication. This can involve drugs that relieve inflammation such as aminosalicylates or steroids; immune system suppressors or immunomodulators, such as azathioprine (Azasan, Imuran) or mercaptopurine (Purinethol, Purixan); biologics, which target proteins that play a role in inflammation; or antibiotics, which fight infection that can develop in the gastrointestinal tract.

Surgery. In some cases, it may be necessary to remove diseased sections of bowel.

Smoking cessation. Smoking is tied to increased severity of Crohn’s disease, so quitting smoking is considered crucial to disease management.

Lifestyle change. To help manage Crohn’s disease, doctors recommend exercising regularly, getting enough sleep and managing stress, which is sometimes linked to Crohn’s disease flare-ups. You should also eat a healthy diet like the Mediterranean diet. “The essential elements of a good diet for Crohn’s are a plant-based diet and avoiding processed foods. You don’t have to become a vegetarian, but eat unprocessed meats,” Jackson suggests.

Using probiotics or prebiotics. They’re not yet proven to help, but there is a lot of interest in using probiotics (colonies of good bacteria) and prebiotics (foods such as fruits, vegetables and legumes that “feed” bacteria) to help maintain healthy gut bacteria.

Will all of these management approaches really keep Crohn’s in check? “If you get yourself in the hands of someone who knows how to manage Crohn’s with medication and you make lifestyle changes, the prognosis is very promising,” Jackson says. “The goal of treatment is to keep the disease at bay so there is minimal impact on your quality of life and career choices.”

More from U.S. News

Crohn’s Disease Life Expectancy

Foods to Eat and Avoid — or at Least Limit — on an Anti-inflammatory Diet

Questions Doctors Wish Their Patients Would Ask

What Is Crohn’s Disease? originally appeared on usnews.com

Update 07/16/21: This story was published at an earlier date and has been updated with new information.

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