Inflammatory Bowel Disease


Medically reviewed by Carina Fung, PharmD, BCPPS

What is inflammatory bowel disease (IBD)?

Inflammatory bowel disease1 (IBD) refers to a group of chronic (lifelong) conditions that cause prolonged inflammation in the digestive tract. The two most common forms of IBD are ulcerative colitis (which affects the colon, or large intestine) and Crohn’s disease (which affects the entire digestive tract).

IBD causes inflammation, swelling, and ulcers (raw or open sores) along various parts of the digestive tract. Where these symptoms occur depends upon the particular form of IBD a patient has. The inflammation characteristic of all forms of IBD causes problems with digestion, nutrient absorption, and waste elimination.

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Although IBD is a lifelong disease, the severity of its symptoms can vary. Many people with the condition experience both symptom-free periods (called remission) and times during which their symptoms are more active. During these periods (known as flares or flare-ups), patients may have severe diarrhea, abdominal pain or cramping, fatigue, weight loss, or bloody stools.

When severe, IBD can be debilitating. There are, however, a number of effective treatments for the disease, ranging from diet management to medication and surgery.

How common is IBD?

An estimated 1.3% of adults in the United States2 (more than 3 million) have been diagnosed with IBD, a significant increase from just 0.9% in 1999.

Crohn’s disease is more common than ulcerative colitis. An extensive study3 conducted from 1940 to 2011 found that approximately 33,000 new cases of Crohn’s disease and 38,000 new cases of ulcerative colitis are diagnosed each year.

While it is estimated that roughly 5%3 of patients with IBD are younger than 20 years old, the majority of people with the condition are diagnosed in their 20s and 30s2.


Many people get confused between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). However, despite their similar names, the two are very different.

IBS4 is a functional gastrointestinal disorder, meaning it disrupts normal bowel function. Unlike IBD, which refers to several particular diseases, IBS describes a group of symptoms.

Inflammatory bowel disease (IBD) causes inflammation, swelling, and ulceration in the intestines. The disease is visible during examinations, such as diagnostic imaging. Irritable bowel syndrome, on the other hand, does not cause inflammation5 and can’t be detected during an exam.

Some cases of IBS cause mild discomfort. But even when IBS does cause significant pain, it does not result in permanent damage to the intestines, as is often the case with IBD.

While the condition may not be as severe as IBD usually is, people with IBS are also more likely to have other functioning disorders, including chronic fatigue syndrome, fibromyalgia, chronic pelvic pain, and temporomandibular joint disorder (TMJ).

Inflammatory bowel disease causes

In the past6, it was thought that inflammatory bowel disease might have been caused by diet and stress. This is not the case; IBD is now known to be a lifelong disease.

While these factors do not cause IBD, however, they are potential aggravating factors. Things like diet and stress alone cannot cause someone to develop IBD, but a patient who was born with IBD may experience flare-ups as a result of high stress or improper diet.

The exact cause7 of inflammatory bowel disease has yet to be determined. It has been thought that genetics8 may play a role in the disease, as people whose family members have IBD are more likely to develop the disease themselves.

Experts are fairly certain, however, that IBD results from malfunctioning in the immune system.

Healthy immune systems identify and attack foreign invaders (called pathogens), like viruses and bacteria. In people with IBD, however, the body mistakenly identifies the tissues in the gastrointestinal tract as pathogens. The resulting immune response causes the body to attack these cells, which leads to inflammation in the digestive tract.

Risk factors for IBD

Certain personal and environmental factors may increase your risk9 of developing IBD, including:

  • Age: IBD is most commonly diagnosed before the age of 30.
  • Family history: Your risk for IBD is increased if you have an immediate family member with the disease.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs): These over-the-counter pain relievers, which include naproxen sodium (generic Aleve), ibuprofen (generic Advil, Motrin), and diclofenac sodium (generic Voltaren), may increase the risk of IBD or worsen the symptoms of IBD in those with the disease.
  • Smoking: Cigarette smoking is the biggest modifiable (controllable) risk factor for Crohn’s disease.
  • Race/ethnicity: People of Hispanic/non-Hispanic white10 and Ashkenazi Jewish descent are at the highest risk of developing IBD.
  • Location and socioeconomic conditions: People living in industrialized countries (especially the United States and Canada) are more likely to develop IBD9, as are those living in suburban areas and those living in poverty10.

Inflammatory bowel disease symptoms

The signs and symptoms of IBD can vary depending on both the severity of your inflammation and where your inflammation occurs.

Common signs and symptoms11 of IBD (seen in both ulcerative colitis and Crohn’s disease) include:

  • Severe/persistent diarrhea
  • Fatigue
  • Abdominal pain/cramping
  • Bloody stools/rectal bleeding
  • Decreased appetite
  • Unintentional weight loss
  • Fever

As previously stated, the signs and symptoms of inflammatory bowel disease may go through periods of remission (being symptom-free) and flare (having worsened or more active symptoms).

It’s extremely important that you seek medical treatment if you experience any of these symptoms or notice any significant or long-lasting changes in your bowel habits.

Complications from IBD

Especially when left untreated, inflammatory bowel disease can lead to serious (and, in some cases, life-threatening) complications.

Potential complications12 of IBD include:

  • Colon cancer: IBD increases the risk of developing colon cancer. Your healthcare provider will likely recommend that you start being screened for colon cancer earlier and more frequently than people without IBD.
  • Inflammation of the skin, eyes, and joints: IBD flares can cause certain inflammatory conditions to occur, including arthritis, eye inflammation (uveitis), and skin lesions.
  • Side effects from IBD medications: Corticosteroids, which are commonly prescribed to help decrease the inflammation caused by IBD, have been associated with osteoporosis, high blood pressure (hypertension), and other health conditions. Additionally, certain medications used to treat IBD have been found to carry a small risk of causing certain types of cancer13.
  • Primary sclerosing cholangitis: This chronic, progressive disorder causes inflammation and scarring in the gallbladder’s bile ducts, causing them to narrow and eventually leading to liver damage.
  • Blood clots: Having IBD increases your risk of developing blood clots in your veins and arteries.

Adults with inflammatory bowel disease are also more likely to have certain chronic conditions and diseases than those without IBD, including14 arthritis, cardiovascular disease, kidney disease, and respiratory disease.

Some complications from IBD are associated with either ulcerative colitis or Crohn’s disease in particular.

Possible complications of ulcerative colitis12 include:

  • Severe dehydration: Diarrhea causes the body to lose fluids very quickly. Prolonged bouts of diarrhea can lead to dehydration, which may require hospitalization.
  • Toxic megacolon: This serious condition occurs when ulcerative colitis causes the colon to rapidly expand and swell. When this occurs, the colon is unable to remove feces and gas from the body. If these substances build up, the large intestine may rupture (which is life-threatening).
  • Perforated colon: This condition, which refers to a hole in the wall of the colon, is most commonly caused by toxic megacolon; however, in some cases, it may occur on its own.

Complications of Crohn’s disease12 may include:

  • Malnutrition: The physical discomfort and intestinal problems caused by Crohn’s disease can make it difficult to eat as usual and prevent the body from absorbing sufficient nutrients. It’s common for people to develop anemia due to vitamin B12 or iron deficiencies as a result of Crohn’s.
  • Bowel obstruction: Unlike ulcerative colitis, Crohn’s disease affects the entire thickness of the intestinal walls. Over time, portions of the bowels can begin to narrow and thicken, potentially blocking digested food from flowing through them. In this case, surgery to remove the obstructed portion of the bowel may be required.
  • Ulcers: Persistent inflammation can cause these open sores to form at any point along the digestive tract, including in the mouth and anus.
  • Fistulas: When an ulcer goes completely through the wall of the intestines, it creates a fistula (an abnormal connection between two hollow spaces in the body). Perianal fistulas (those near or around the anus) are the most common type. A fistula may become infected and form an abscess, potentially causing further complications.
  • Anal fissure: An anal fissure is a small tear that occurs in the tissue lining the anus or in the skin around the anus. This has the potential to become infected and may cause a perianal fistula to form.

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