Inflammatory Bowel Disease (IBD)

Including Ulcerative Colitis, Crohn's Disease and Pouchitis

IBD is a broad term that describes conditions characterized by an abnormal response to the body’s immune system and inflammation of the gastrointestinal (GI) tract. The two most common IBDs are ulcerative colitis and Crohn’s disease. In ulcerative colitis, inflammation affects the large intestine; in Crohn’s disease, it affects the entire digestive tract. IBDs are chronic, life-long conditions that currently can be treated but not cured.

Common IBDs, which will be covered in this section, include: ulcerative colitis, Crohn’s disease, and pouchitis.


  • Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, affects as many as 1.6 million Americans, most of whom are diagnosed before age 35.
  • IBD is characterized by inflammation of the lining of the intestine. As the lining of the intestine becomes inflamed and ulcerated, it loses its ability to adequately process food and waste or absorb water, resulting in loose stools (diarrhea), and in severe cases, weight loss.
  • As many as 70,000 new cases of IBD are diagnosed in the United States each year.
  • Pouchitis occurs in about half of patients who undergo ileoanal anastomosis (IPAA) surgery for ulcerative colitis at least once in their lifetimes.
  • Up to 40% of patients with IPAA develop pouchitis every year.

Natural History

  • Seventy percent of patients who have active disease in a given year will have another episode of active disease in the following year.
  • People with IBD often go through periods when the disease is quiet with few or no symptoms (remission), alternating with times when the disease is active and causing symptoms (flares).
  • Only 30% of those in remission in a given year will have active disease in the following year.
  • The longer a person with ulcerative colitis remains in remission, the less likely he or she is to experience a flare-up of the disease in the following year.
  • Unidentified environmental factors serve as the “trigger” that initiates the harmful immune response in the intestines.

Etiology and Disease Pathogenesis

  • While the exact cause of IBD is not entirely understood, it is known to involve an interaction among genes and the immune system. The intestinal microbiome may play a critical role in the chronic inflammatory response characteristic of IBD as well.
  • In people with IBD, the immune system mounts an inappropriate response to the intestinal tract, resulting in inflammation.
  • This abnormal immune system reaction occurs in people who have inherited genes that make them susceptible to IBD.
  • The cause of pouchitis is not entirely clear, but it almost always occurs in patients with ulcerative colitis or another form of colitis, and sometimes in those with familial adenomatous polyposis (FAP), a genetic (inherited) condition in which many polyps form in the colon. Pouchitis can also occur in patients undergoing IPAA surgery.

Identifying Patients

  • Although Crohn’s disease and ulcerative colitis can occur at any age, people are more frequently diagnosed between the ages of 15 and 35.
  • The median age of diagnosis for ulcerative colitis and Crohn’s disease is 35 years and 30 years respectively.
  • IBD affects men and women equally. However, most studies show that ulcerative colitis is more common in men than in women.
  • Men are more likely than women to be diagnosed with ulcerative colitis in their 50’s and 60’s.
  • Pouchitis is most commonly diagnosed through an endoscopic examination of the inside of the ileum. Imaging studies such as contrast pouchography may also be used to determine diagnosis.


  • The symptoms of IBD vary from person to person, may change over time, and can range from mild to severe.
  • Most people with Crohn’s disease or ulcerative colitis experience an urgency to have a bowel movement and have crampy abdominal pain.
  • Inflammation can cause small sores (ulcers) to form in the colon and rectum. These can join together and become large ulcers that bleed, resulting in bloody stools.
  • Patients with pouchitis can develop a wide range of clinical presentations, including increased stool frequency, urgency, tenesmus, incontinence, nocturnal seepage, abdominal cramping, and pelvic discomfort.

Potential Complications of IBD

Complications of ulcerative colitis include:

  • Heavy, persistent diarrhea, rectal bleeding, and pain.
  • Perforated bowel—chronic inflammation of the intestine may weaken the intestinal wall to such an extent that a hole develops.
  • Toxic megacolon—severe inflammation that leads to rapid enlargement of the colon.

Complications of Crohn’s disease include:

  • Fistula—ulcers on the wall of the intestine that extend and cause a tunnel (fistula) to another part of the intestine, the skin or another organ.
  • Stricture—a narrowing of a section of intestine caused by scarring, which can lead to an intestinal blockage.
  • Abscess—a collection of pus, which can develop in the abdomen, pelvis, or around the anal area.
  • Perforated bowel—chronic inflammation of the intestine may weaken the wall to such an extent that a hole develops.
  • Malabsorption and malnutrition, including deficiency of vitamins and minerals.

Complications of pouchitis include:

  • Antibiotic resistance resulting from antibiotic treatment.
  • In some cases, surgical removal of the pouch or permanent diversion may be necessary.

IBD and Pouchitis Resources for In-depth Information