What Is Inflammatory Bowel Disease (IBD)?

What Is Inflammatory Bowel Disease (IBD)?

“Inflammatory bowel disease” is an umbrella term used to describe chronic inflammatory disorders of the tissues in the digestive tract (also called the gastrointestinal tract). This inflammation can cause severe pain.

“Inflammatory bowel disease” is used to describe both Crohn’s disease and ulcerative colitis (UC), two of the most common forms of IBD. Inflammatory bowel diseases are common, with an estimated 3.1 million adults in the United States having an IBD diagnosis.

Inflammatory Bowel Disease (IBD) vs. Irritable Bowel Syndrome (IBS)

Inflammatory bowel disease is different from irritable bowel syndrome. Irritable bowel syndrome is a chronic syndrome characterized by a group of symptoms, while IBD specifically refers to various chronic inflammatory disorders of the digestive tract, also referred to as the gastrointestinal (GI) tract.

IBS is classified as a functional gastrointestinal disorder, which means there is a disturbance in bowel function. Symptoms may include diarrhea, constipation, or alternating between both, as well as bloating, gas, cramping, or mucus in the stool.

People with IBS may experience chronic abdominal pain. Some people experience only mild symptoms, while others have more severe symptoms. People can have both IBS and IBD.

Types of IBD


There are three types of IBD:

  • Crohn’s disease — Causing swelling and pain in the digestive tract, Crohn’s disease can affect the entire digestive tract, from the mouth to the anus. However, it usually affects the end of the ileum, the small intestine (also known as the small bowel), and the colon (part of the large intestine).
  • Ulcerative colitis causes inflammation of the innermost part of the large intestine, in the colon or rectum. UC typically starts in the rectum, which is close to the anus. The severity of the disease depends on the location and amount of inflammation.
  • Microscopic colitis — Causing chronic inflammation that’s usually only detectable using a microscope, microscopic colitis results from intestinal wall irritation. This rare colitis typically causes watery, frequent diarrhea and can be harder to diagnose.

Stages of IBD


The different types of IBD can be classified into stages based on the severity and progression of the disease.

Stages of Crohn’s disease

Crohn’s disease is chronic and can progress (become worse) over time. It’s classified into three stages:

  • Mild to moderate Crohn’s disease usually involves diarrhea or abdominal pain with no other symptoms. Some people with mild to moderate Crohn’s disease don’t require treatment.
  • Moderate to severe Crohn’s disease may involve diarrhea or abdominal pain. Treatments for mild to moderate Crohn’s disease, such as antidiarrheals, generally won’t alleviate symptoms.
  • Severe Crohn’s disease can cause constant pain and discomfort and frequent bathroom use. Surgery may be required.
Stages of ulcerative colitis

Ulcerative colitis is classified into four distinct stages:

  • Mild ulcerative colitis may come with mild abdominal pain and up to four loose stools per day, as well as bloody stools.
  • Moderate ulcerative colitis can result in more serious symptoms, including four to six loose stools a day, moderate pain, bloody stools, and anemia.
  • Severe ulcerative colitis can cause up to six loose stools daily, which may be bloody. People may also experience fever, rapid heart rate, and anemia. Pain may be intense.
  • Fulminant ulcerative colitis is a somewhat rare and very severe form of ulcerative colitis. People with fulminant UC may have up to 10 loose stools per day, constant blood in stools, and tenderness or distention in the abdomen (swelling beyond its normal size). Complications can be fatal, requiring immediate treatment.
Stages of microscopic colitis

Microscopic colitis is generally not classified into different stages, as symptoms can begin suddenly or gradually, and can vary greatly in severity.

Signs & Symptoms of IBD


The signs and symptoms of inflammatory bowel disease can vary depending on the type, stage, and severity.

Common IBD symptoms and signs include:

In biologically female people, signs and symptoms of inflammatory bowel disease may include:

  • Painful or irregular periods
  • Bone loss and osteoporosis (a disease in which the bones weaken, increasing the likelihood of them breaking)
  • Worsened pain or diarrhea during menstruation
  • Lower fertility
  • Pain during sex
  • Anemia

In children, IBD can present with the same signs and symptoms as in adults. However, in children, symptoms are usually more extensive. Less typical signs in kids include:

  • Poor growth
  • Delayed puberty

The experts at NewYork-Presbyterian can help treat your or your child’s IBD symptoms, creating a personalized treatment plan for every patient to improve their health and quality of life.

Causes & Risk Factors of IBD

Causes & Risk Factors

Inflammatory bowel disease is an autoimmune disorder, meaning the immune system mistakenly attacks healthy tissue in the body.

Research is ongoing to determine exactly what triggers IBD flare-ups and causes intestinal inflammation, but risk factors may include:

  • Immune system response to viruses and bacterial infections can cause inflammation in the gastrointestinal tract. This may lead to IBD and trigger flare-ups, though research is ongoing.
  • Genetic factors, such as a family history of IBD, appear to make someone more likely to develop IBD themselves.
  • Environmental triggers may also play a role in IBD. Lifestyle factors such as cigarette smoking, stress, medication use (specifically, nonsteroidal anti-inflammatory drugs or NSAIDs), depression, and certain foods may trigger IBD.



Inflammatory bowel disease can lead to various complications, including:

  • Abscesses, or collections of pus, can form when inflammation spreads deep into the wall of the intestine, causing infection.
  • Stricture, a narrowing of a part of the intestine, occurs when scar tissue forms in the intestine wall. This occurs more frequently with Crohn’s disease than it does with UC.
  • Blood clots are three to four times more likely to occur in people with IBD than in people without IBD. Genetics and other factors likely contribute to this heightened risk, and research is ongoing. Blood clots can be life-threatening.
  • Severe dehydration can also pose an increased risk in people with IBD. Some people experience dehydration when having flare-ups with diarrhea, vomiting, or fever-induced sweating.
  • Anal fistulas are small tunnels that form between the inside of the anus and the skin surrounding the anus, creating a painful, tender bump around this area. These can be very disabling. Anal fistulas are more common in people with Crohn’s than people with colitis.
  • Kidney stones may form in people with IBD due to chronic inflammation, dehydration, or malabsorption, a condition in which the small intestine cannot absorb nutrients properly. Kidney stones are more common in people with Crohn’s than people with UC.
  • Primary sclerosing cholangitis (PSC) is a chronic liver disease in which the bile ducts inside and outside the liver become inflamed and scarred, leading to blockage and narrowing. This can lead to bile buildup and damage to the liver. Most PSC patients have IBD.
  • Higher risk of colon cancer can occur in people with an inflammatory bowel disease involving the colon.
  • Skin, eye, and joint inflammation are referred to as extraintestinal manifestations in IBD, meaning inflammation is not only occurring not only inside the digestive system but also in other parts of the body.
  • Medication side effects can manifest as headaches, diarrhea, abdominal pain, respiratory infection, vomiting, nausea, rash, fever, arthralgia (joint pain), and more. Reactions may occur more often when beginning medication and then lessen over time and will vary greatly depending on the specific medicine and individual patient.



The cause of IBD is still not clearly understood, so there is no definitive way to prevent the disease. However, there are a few ways that may help reduce the risk of developing inflammatory bowel disease, including:

  • Eating smaller, healthy meals
  • Ceasing cigarette smoking
  • Identifying and avoiding dietary triggers (foods or beverages that seem to cause irritation or pain)
  • Managing stress through tactics like meditation, walking, reading, exercising, engaging in talk therapy, or seeking psychiatric care
  • Getting recommended vaccinations and taking proper precautions to help prevent infections and viruses, including COVID-19
  • Getting screened for colon cancer, especially if you think you may have symptoms of IBD
  • Talking to your doctor about how to prevent cervical cancer (in biologically female people)
Get Care

Trust NewYork-Presbyterian for IBD Care

The experts at NewYork-Presbyterian have extensive experience caring for patients with inflammatory bowel disease. We’ll work with you to create a treatment plan that takes into account your specific symptoms, lifestyle, and needs.

If you think you’re experiencing symptoms of IBD, it’s important to seek medical care to prevent symptoms from worsening and help improve your quality of life. Reach out to the team at NewYork-Presbyterian to make an appointment.