What Is Inflammatory Bowel Disease?

Inflammatory bowel disease (IBD) is a condition that involves chronic inflammation in all or part of the digestive tract. Often painful and debilitating, IBD can lead to life-threatening complications as well as increase the risk for colon cancer.

More than 3 million people have IBD, according to a recent government survey. The two most common forms of IBD are ulcerative colitis and Crohn’s disease.

In Crohn's, inflammation can occur anywhere in the digestive tract, from the mouth to the anus. By contrast, ulcerative colitis only involves inflammation of the large intestine, or colon, according to Dr. David Hudesman, a gastroenterologist and director of the Inflammatory Bowel Disease program at New York University Langone Medical Center.

"They are two distinct conditions, but there's a lot of overlap of the symptoms and physiology," Hudesman told Live Science.

IBD is not the same as irritable bowel syndrome (IBS), which does not cause inflammation or damage in the intestines. It is estimated that as many as 1 million Americans suffer from IBD, and most sufferers begin to feel symptoms between the ages of 15 and 30.

Symptoms of IBD

With IBD, the intestines (small, large and bowels) become inflamed, including redness and swelling. Related symptoms, which can range from mild or severe, include:

• Severe or chronic abdominal pain
• Diarrhea, often bloody
• Sudden weight loss
• Lack of appetite
• Rectal bleeding

IBD can also have symptoms unrelated to the gastrointestinal tract, including

• Joint pain
• Skin rashes
• Eye pain
• Mouth sores
• Fever

Symptoms can come on suddenly and flare up at random times, often going away for months or even years at a time. These are known as “relapses” or “flare-ups.” When symptoms are gone (though never permanently, as IBD is chronic), the patient is considered to be in remission.

Ulcerative colitis and Crohn’s disease have such similar symptoms that doctors have a hard time diagnosing what kind of IBD a patient might have.

The most common symptoms of Crohn's are diarrhea (sometimes blood) and abdominal pain, and sometimes nausea and vomiting, whereas the main symptoms of ulcerative colitis are bloody diarrhea or stool, an urgent/frequent need to go to the bathroom, and incomplete evacuation of bowel movements, Hudesman said.

The primary difference between Crohn's and ulcerative colitis is the part of the digestive tract that they affect.

Crohn’s disease causes patchy inflammation on all layers of the intestinal wall, whereas ulcerative colitis affects only the top layer of the large intestine. Ulcerative colitis causes swelling and ulcers to form on the surface of the lining, which bleed and produce pus. In severe cases, the ulcers can weaken the intestine and cause a hole, spilling the bacteria-laden contents of the large intestine into the abdominal cavity or the patient’s bloodstream.

Though Crohn's can affect any of the digestive tract, it most commonly affects the end of the small bowel (the ileum) and the beginning of the colon. With Crohn’s disease, the inflammation causes swelling and scar tissue to thicken the intestinal wall. The passageway for food becomes narrowed (known as a stricture) and deep ulceration can cause tunnels (known as fistulas). These fistulas can connect the intestines to organs that they shouldn’t connect to, like the bladder or the skin.

In addition to the damaging the digestive tract, IBD can create many other health problems for those afflicted. The loss of blood from the intestines can cause anemia, or below-normal levels of healthy red blood cells. Other problems include arthritis and joint pain, weak bones, eye problems, gallstones, skin issues, kidney stones, and delayed puberty and growth issues in children. Many of these problems are caused by the malabsorption of nutrients, since the digestive tract is not working properly. IBD flareups can also cause inflammation in other parts of the body. Some of these symptoms will improve when the IBD is properly treated.

Cause & diagnosis

Although doctors don't know exactly what causes IBD, it has a genetic predisposition (to date, more than 160 genes have been linked to the disease), but there is usually some trigger in the environment, Hudesman said — whether it's travel, antibiotics, or infection — that causes a shift in a person's bacteria that results in an abnormal immune response.

Some medical conditions are associated with IBD. For example, people with psoriasis (a chronic inflammatory skin condition) are more likely to develop IBD, possibly because of problems with the immune system.

Though stress and diet can worsen IBD symptoms, they do not cause IBD.

There are a number of ways to diagnose IBD. Blood tests can find signs of inflammation and anemia, while stool tests can test for blood and signs of infection. Doctors may also use a long thin tube with a lighted camera to look into a person’s intestine — either a sigmoidoscopy, which goes as far as the lower part of the large intestine, or a colonoscopy, which goes through the entire large intestine and the last part of the small intestines — and take a biopsy of tissue.

A less invasive way to look for intestinal problems is an X-ray after the patient has consumed liquid barium to coat the digestive tract lining. Computerized axial tomography (CAT) scans and capsule endoscopies also provide insight into any damage that might be occurring to the digestive tract.

Treatment for IBD

Treatment for IBD varies per patient. Some may require medication, which can range from corticosteroids to biologic therapies and antibiotics. For example, the drug Mesalamine, delivered as either a rectal enema, suppository or pill, works to open up the small intestine, Hudesman said. Patients with more severe flareups may require steroids such as prednisone, but this can have side effects. Immunosuppressants and biologics may also be prescribed, Hudesman said.

For the most part, changes in diet, reducing stress, and getting enough rest are universal ways of treating symptoms. Some patients avoid greasy foods, cream sauces, processed meat products, spicy foods and high fiber foods.

Other patients with more serious prognoses may require surgery. With ulcerative colitis, 25 to 40 percent of patients will need surgery, which can include complete removal of the large intestine. Patients who undergo this type of surgery will need to have pouches attached either internally or externally, for waste removal.

With Crohn’s disease, 65 to 75 percent of patients will need surgery to correct strictures, fistulae or bleeding in the intestines. A strictureplasty widens the strictures without removing any part of the small intestine, and a bowel resection involves removing parts of the intestine and sewing the healthy ends together. Crohn’s patients can also have their large intestine removed but require an external pouch in its place.

Living with IBD can be stressful and taxing, because patients may miss school or work, or experience depression and anxiety. There are hundreds of support groups for people with Crohn's disease and ulcerative colitis. In these support groups, patients and their loved ones gather to share their stories, seek emotional support and connect with a community of people who experience similar challenges. There are also online communities where patients can chat in a forum and share tips on managing the condition 24/7.

"These conditions are not curable," Hudesman said. "But if patients get on the appropriate medications, they can feel well."

Additional resources:

• The Mayo Clinic website is a useful reference for patients with IBD
• For more on the difference between Crohn's disease and ulcerative colitis, on the Crohn's & Colitis Foundation of America website
• To find out about research on IBD, see the U.S. Centers for Disease Control and Prevention website 

This article was updated on Nov. 7, 2018 by Laura Geggel, Live Science Senior Writer. 

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