Understanding What Ulcerative Colitis Is and How It Develops

Ulcerative colitis (UC) is a chronic condition that causes inflammation in the colon and can cause other complications throughout the body. It is an inflammatory bowel diseases (IBD), a category that also includes Crohn’s disease and indeterminate colitis.

The forms of IBD are sometimes confused for one another because the symptoms are similar. They are, however, different in the ways they affect the body and, in some cases, how they are treated.

This article will discuss what happens in the body when ulcerative colitis develops, how common the condition is, and its symptoms, diagnostic process, and treatment.

A person lying on a table with acupuncture needles in their back (How is Ulcerative Colitis Treated?)

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What Happens During Ulcerative Colitis

The cause of ulcerative colitis, which is called pathophysiology, is not well understood. It's thought that it may be connected to something causing the bacteria and other microbes that normally live in the colon to be out of balance, leading to an immune response and inflammation.

However, there is research underway that has started to uncover some of the reasons why people might develop the disease, including the following.

Genetic Predisposition

One of the factors involved in ulcerative colitis is that it does run in families. However, it’s not as simple as being passed down from parent to child. In fact, most people with UC don’t have a family member who has the disease. 

So far, more than 200 genes have been found to be involved in the development of IBDs. This has led scientists to believe that several factors can cause ulcerative colitis to develop.

Inflammation of the Colon

The most prominent sign of ulcerative colitis is inflammation in the colon. Inflammation causes the formation of ulcers in the lining of the colon. This can lead to symptoms of diarrhea, bloody stools, pain, and an urgency to go to the bathroom.

Immune Response

One of the factors involved in developing IBD is a problem with the immune system that causes the immune system to attack the colon. The attack leads to inflammation in the lining of the colon. This can also lead to inflammation in other areas of the body, including the skin, eyes, liver, and joints.

Environmental Factors

It’s thought that there are certain triggers in the environment that may lead to the development of IBD. These seem to be different based on geography.

Some of the factors that have been identified include cigarette smoking, a history of gastroenteritis (sometimes called the stomach flu), and certain drugs (including oral contraceptives, hormone replacement therapy, and nonsteroidal anti-inflammatory drugs, or NSAIDs).

How Common Ulcerative Colitis Is 

Ulcerative colitis is a common disease. In fact, cases are increasing throughout the world. The prevalence per every 100,000 people is estimated to be:

  • Europe: 505
  • Canada: 248
  • United States: 214


The signs and symptoms of ulcerative colitis may vary slightly from person to person. However, the most common symptoms include:


The diagnosis of ulcerative colitis is made after your healthcare provider looks into your symptoms and performs tests to find out what is causing them. Endoscopic tests that use a lighted, flexible tube inserted into the body (such as sigmoidoscopy or colonoscopy), biopsies (tissue taken from the lining of the colon to be tested in a lab), and ruling out other diseases to explain your symptoms all help make the diagnosis.


The treatments for ulcerative colitis can include medications, surgery, complementary therapies, and diet and lifestyle changes.


The medications used to treat ulcerative colitis will depend on several factors, including how serious the disease is, the age of the patient, and doctor and patient preferences. Some of the classes of medications used are:

  • Aminosalicylates: These medications can be given in several forms, including pills, enemas, and suppositories. Some of the names are Azulfidine (sulfasalazine) and Canasa (mesalamine). 
  • Corticosteroids: In more serious disease, steroids such as prednisone or Entocort (budesonide) might be prescribed. These drugs may have adverse effects that can be long term and permanent, so they’re usually only used for a short period.
  • Immunomodulators: Medications that target the immune system such as Purinethol (6-mercaptopurine), Imuran (azathioprine), or Trexall (methotrexate) might also be prescribed. But these are used less frequently in ulcerative colitis than in Crohn’s disease. 
  • Biologics: These drugs are used to treat ulcerative colitis that is moderate to severely active. These include Entyvio (vedolizumab), Humira (adalimumab), Remicade (infliximab), Simponi (golimumab), and Stelara (ustekinumab).
  • Janus kinase (JAK) inhibitors: This newest class of drugs includes Xeljanz (tofacitinib) and may be used in moderate to severe ulcerative colitis.


Surgery may be used to treat ulcerative colitis. Removing the colon (colectomy) is done for a variety of reasons, including if there’s a risk of colon cancer or other complications such as a perforation (hole) in the large intestine. Having a poor quality of life due to symptoms is another reason for having surgery.

After a colectomy, another way for stool to leave the body must be created. That means adding either an ileostomy or an ileal pouch-anal anastomosis (IPAA).

In an ileostomy, a stoma is created in the abdomen for stool to leave the body, over which an appliance is worn. In an IPAA (commonly called a J-pouch), the small intestine is connected to the anus and stool leaves the body through the bottom.

Complementary Therapies

People with ulcerative colitis often try nondrug treatments to manage their disease. Some that may help people who live with ulcerative colitis manage their disease include acupuncture, mind-body interventions (mindfulness, meditation, relaxation training), and yoga.

Always check with your healthcare provider about using supplements to ensure they don’t interfere with other therapies.

Diet and Lifestyle

People with ulcerative colitis often try diets to manage the symptoms of their disease. In some cases, during a flare-up, dietary changes may be recommended by a physician or a dietitian. Other more comprehensive diet plans might also be used to manage symptoms, with the help of a dietitian.

Sufficient data on diet in ulcerative colitis are still lacking. However, one recent study in Crohn’s disease has shown that both the specific carbohydrate diet (a restrictive diet that is free of grains and processed foods) and the Mediterranean diet (made up of healthy fats, whole grains, plant-based foods, and lean poultry or fatty fish, such as salmon and albacore tuna) were helpful in reducing symptoms.

Colon Cancer and Ulcerative Colitis

Long-term ulcerative colitis is associated with a risk of colon cancer. However, as treatments improve and it becomes more manageable to keep the inflammation caused by ulcerative colitis at bay, the risk has lowered. Regular colonoscopies with biopsies are usually recommended to keep watch for any changes in the cells of the colon.


Ulcerative colitis is a condition that causes inflammation (swelling and redness) in the colon and sometimes in other areas of the body. It’s not known what causes it to start, but it’s thought that both genetics and other factors cause the good microbes that live in the colon to get out of balance.

There are many drugs and complementary treatments that can help people with ulcerative colitis keep symptoms under control and have a good quality of life.

A Word From Verywell

What causes ulcerative colitis is still not known. However, it does seem to be a complex interaction of genetics and environmental factors. Stress is not a cause of ulcerative colitis, though it can make symptoms worse. If you have ulcerative colitis, you have many good choices for disease management and can expect to live a full, normal life. 

Frequently Asked Questions

  • What is IBD?

    Irritable bowel disease (IBD) is a collection of diseases that affect the immune system. They cause inflammation in the digestive system. In some people, inflammation may occur in other parts of the body, such as the eyes, skin, and joints.

  • What is the difference between ulcerative colitis and Crohn’s disease?

    Crohn's disease and ulcerative colitis are both forms of IBD. The main difference between the two is that ulcerative colitis affects the colon and Crohn's disease can affect any part of the digestive system. In addition, blood in the stool is less common and abdominal pain is more common in Crohn's disease than in ulcerative colitis.

  • What is the main cause of ulcerative colitis?

    There are probably many causes of ulcerative colitis. But it's thought that they may all stem from an imbalance in the microbiome (microbes that can be both helpful and potentially harmful) of the colon. Something causes the bacteria and other microbes (such as viruses and fungi) that normally live there to be out of balance.

  • Is ulcerative colitis considered an autoimmune disease?

    The various forms of IBD are probably better described as immune-mediated diseases rather than autoimmune diseases. This is because no autoantibodies have been found to be connected to IBD.

  • Which is the best diet for ulcerative colitis?

    Because every person with IBD experiences the disease differently, there is no one diet that is recommended for all people who live with the disease. In addition, there hasn't been much study to recommend any one diet over another.

    Dietitians often recommend a modified Mediterranean diet for their patients who are in remission (without symptoms). However, patients should always work with their medical team on diet to avoid vitamin deficiencies and malnutrition.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.