What Is Crohn’s Disease?

What Is Crohn’s Disease?

Crohn’s disease is a form of inflammatory bowel disease (IBD), an umbrella term used to describe disorders involving chronic inflammation of tissues in the digestive tract. Crohn’s disease causes inflammation anywhere along the gastrointestinal (GI) tract, most commonly in the small and large intestines.

The inflammation caused by Crohn’s disease can result in abdominal pain, severe diarrhea, nausea, loss of appetite, weight loss, fatigue, malnutrition, and more.

Ulcerative colitis (UC) vs. Crohn’s disease

Both Crohn’s disease and ulcerative colitis are forms of inflammatory bowel disease. Crohn’s disease can affect the entire digestive tract, from the mouth to the anus. There are healthy parts of the intestine in between inflamed areas.

Ulcerative colitis, on the other hand, causes continuous inflammation of the innermost part of the large intestine in the colon or rectum. It typically begins in the rectum, which is close to the anus.

The other type of IBD is called microscopic colitis. This rare condition results from intestinal wall irritation and is usually only detectable using a microscope.

Types of Crohn’s Disease


There are six major types of Crohn’s disease:

  • Ileocolitis is the most common type of Crohn’s disease. It affects the ileum (the lower part of the small intestine) and part of the colon. This type can cause diarrhea and cramping, middle or lower abdominal pain, and severe weight loss.
  • Ileitis affects the last section of the ileum. Symptoms are usually similar to those of ileocolitis. In severe cases, complications such as abscesses in the lower right of the abdomen can occur, as well as fistulas, which form when inflammation causes sores on the inside wall of the intestine or nearby organs.
  • Gastroduodenal Crohn’s disease affects the stomach and duodenum (the first part of the small intestine, immediately beyond the stomach). Nausea, vomiting, weight loss, and loss of appetite may occur.
  • Jejunoileitis causes patchy inflammation in the jejunum, the second part of the small intestine, between the ileum and the duodenum. People may have diarrhea, as well as abdominal pain and cramps after eating. In more severe cases, or after prolonged intestinal inflammation, anal fistulas (connections or “tunnels” between the anus and the skin around the anus) can develop.
  • Crohn’s colitis, also known as Granulomatous colitis, affects only the colon. Diarrhea, rectal bleeding and abscesses, fistulas, and ulcers may occur. Joint pain and skin lesions are more likely to develop with this type of disease.
  • Perianal Crohn’s disease affects the anus and typically results in ulcers, abscesses, fistulas, and stenosis (narrowing) of the anal canal.
  • Aphthous ulcers (canker sores) in the mouth and Crohn’s of the esophagus can also occur as a result of Crohn’s disease.

Stages of Crohn's Disease


Crohn’s disease is classified into three stages:

  • Mild to moderate Crohn’s disease usually involves diarrhea or abdominal pain, with no other symptoms. People can usually eat, drink, and move as usual with minimal interference to everyday activities. 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, along with symptoms and complications such as nausea, fever, and anemia, a condition in which the body does not produce enough red blood cells, which may cause one to feel dizzy, weak, or tired. Treatments and medicine for mild to moderate Crohn’s disease, such as antidiarrheals, generally won’t alleviate symptoms. This differentiates this condition from irritable bowel syndrome (IBS).
  • Severe Crohn’s disease can significantly disrupt daily life. People with severe disease may be in constant pain and discomfort and have to use the bathroom frequently. Inflammation occurs often, and tissues are at risk of permanent damage, which requires advanced medical therapy and/or surgery.

It’s important to note that Crohn’s disease is chronic and can progress (become worse) over time. However, symptoms may also come and go, with periods of severe symptoms (flare-ups) and periods of relief (remission).

Signs & Symptoms of Crohn's Disease


There are several signs and symptoms associated with Crohn’s disease.

Some common Crohn’s disease symptoms include:

  • Diarrhea is common in the early, moderate, and severe stages of the disease. Severe, frequent diarrhea can occur in the severe stage.
  • Fever can occur as the disease progresses and the intestine becomes inflamed, or as a result of complications from the disease or side effects from medication.
  • Fatigue is a common symptom of Crohn’s and may occur both during both flare-ups and remission.
  • Bloody stools may occur as a result of bleeding in the lower digestive tract. This is often an early symptom.
  • Leakage around anus may occur due to inflammation.
  • Abdominal pain is very common across all stages of Crohn’s disease and is often an early symptom.
  • Reduced appetite, weight loss, and malnutrition can occur as a result of diarrhea, vomiting, and nausea. Unintentional weight loss is often an early symptom of the disease.
  • Mouth sores can develop around the base of the gums, as well as facial, gum, and lip swelling and redness.
  • Cramps in the abdomen may occur at any stage and often happen an hour or two after eating, or during a flare-up of symptoms.
  • Eye problems may occur in people with more advanced stages of the disease, in the form of episcleritis, inflammation of the white part of the eye called the sclera. This can result in redness and irritation. Eye issues can sometimes result in pain and in rare, severe cases, even vision loss.
  • Joint inflammation and joint pain can occur as the disease progresses, with the immune system or damaged digestive tract tissue releasing chemicals that cause swelling and other symptoms in the joints.
Crohn’s disease in women

People assigned female at birth are just as likely as people assigned male at birth to get Crohn’s disease. However, those assigned female at birth may be more likely to experience certain symptoms or may have different symptoms, such as:

  • Worsened pain or diarrhea during sex
  • Painful or irregular periods
  • Osteoporosis or weakened bones
  • Lower fertility
  • Painful sex
  • Anemia

The digestive specialists at NewYork-Presbyterian can help treat any signs and symptoms of Crohn’s disease, working closely with every patient to improve overall health and quality of life.

What Causes Crohn’s Disease?


Crohn’s disease is an autoimmune disorder, meaning the immune system mistakenly attacks healthy tissue in the body. There is no known cause of Crohn’s disease and research is ongoing.

However, some risk factors may increase the risk of developing Crohn’s disease as well as trigger flare-ups, including:

  • Immune system response to viruses and bacterial infections can cause inflammation in the gastrointestinal tract. This may lead to Crohn’s disease and trigger flare-ups.
  • Genetic factors, such as a family medical history of Crohn’s, appear to make someone more likely to develop the disease. The risk is substantially higher in people whose parents both have Crohn’s.
  • Ethnicity can play a role in who is more likely to develop Crohn’s. People of Eastern European backgrounds, including Jews of European descent, may be more likely to have the disease. In recent years, there have been more reports of African Americans with Crohn’s.
  • Age can be a factor as well; although people can develop Crohn’s at any age, it’s more common in people age 15–35 and 50–80.
  • Environmental triggers may also play a role in Crohn’s disease. Lifestyle factors such as cigarette smoking, stress, use of nonsteroidal anti-inflammatory medications (NSAIDs) such as ibuprofen, depression, and certain foods — such as those high in fat or sugar — may trigger it. Some people find that alcohol, fried food, hot or spicy foods, caffeinated beverages, and other environmental factors are triggers.



Crohn’s disease can cause various potentially serious complications, including:

  • Abscesses, or collections of pus, can form when inflammation spreads deep into the wall of the intestine, causing infection. Abscesses can lead to fistulas between organs as well.
  • 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.
  • Bowel obstruction may occur in some people with Crohn’s, affecting the entire thickness of the intestinal wall.
  • Stricture, a narrowing of a part of the intestine, can occur when scar tissue forms in the intestine wall.
  • Blood clots are more likely to occur in people with Crohn’s than in people without. Genetics and other factors likely contribute to this heightened risk, and research is ongoing. Blood clots can be life-threatening.
  • Kidney stones may form in people with Crohn’s disease due to chronic inflammation, dehydration, or malabsorption, a condition in which the small intestine cannot absorb nutrients properly. When the small intestine is explicitly affected, the body can’t absorb fat as well, which can cause a specific type of kidney stone called calcium oxalate stones.
  • Higher risk of colon cancer can occur in people with Crohn’s disease involving the colon.
  • Malnutrition as a result of symptoms including diarrhea and vomiting, as well as subsequent loss of appetite or dehydration, can also pose a problem for people with Crohn’s.
  • Skin, eye, and joint inflammation are referred to as extraintestinal manifestations of Crohn’s, meaning inflammation occurs 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.
  • Toxic megacolon is a rare, life-threatening complication of severe colon disease or infection, which can occur when inflammation spreads into the deeper layers of the colon. People with Crohn’s are at higher risk of this condition.
Pregnancy and Crohn’s disease

Many people with Crohn’s disease become pregnant and have healthy pregnancies and deliveries. Some people’s Crohn’s symptoms even improve while they’re pregnant, with fewer flare-ups and less discomfort.

However, it’s important to note that it may be harder to become pregnant when you have active Crohn’s than it would be in remission (when the disease is inactive). If you’re thinking about becoming pregnant, talk with your gastroenterologist as well as your OB-GYN.



The cause of Crohn’s is still not clearly understood, so there is no definitive way to prevent the disease. However, there are a few steps you can take that may help reduce the risk of flare-ups, including:

  • Eating smaller, healthy meals
  • Ceasing cigarette smoking
  • Exercising regularly
  • Avoiding taking NSAIDs, as research shows they may irritate the stomach, triggering flare-ups
  • Identifying and avoiding dietary triggers (foods or beverages that seem to cause irritation or pain)
  • Managing stress through tactics like meditation, walking, reading, engaging in talk therapy, or seeking psychiatric care
  • Getting recommended vaccinations and taking proper precautions to help prevent infections and viruses, including COVID-19
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Trust NewYork-Presbyterian for Crohn’s Disease Care

NewYork-Presbyterian has the knowledge and experience needed to treat all kinds of Crohn’s disease, as well as other types of digestive and kidney diseases. We work closely with every patient to find treatments that will work best for their specific needs, including surgical treatment as needed. Our expert team is committed to minimizing symptoms and improving overall health. Contact us today to learn more and make an appointment.