Colitis is an inflammation of the colon that can cause urgent bowel movements, abdominal pain, and bloody diarrhea. While some forms of colitis are temporary and resolve quickly, others can last for years and significantly affect daily life. Understanding the causes, symptoms, and management of colitis can help those affected navigate this challenging condition.

What Is Colitis?

Colitis refers to inflammation in the colon, which is the main part of the large intestine. The colon represents the last leg of the journey food takes through the digestive system, where digested food is transformed into waste. When inflammation occurs in the colon, the tissues swell and become irritated, causing discomfort and disrupting normal bowel function.^[1]

The inflammation makes the colon’s lining swell and causes various symptoms that can interfere with quality of life and make it difficult to carry out normal daily activities. Depending on the type and severity, colitis can affect just the end of the colon near the rectum, or it can spread throughout the entire large intestine.^[1]

There are different types of colitis with varying degrees of severity. Some forms are short-lived and easy to treat, similar to what happens when someone gets food poisoning. Other types, particularly inflammatory bowel diseases (which are long-term conditions that cause repeated inflammation), are more difficult to treat and require ongoing management. Colitis becomes more serious when it doesn’t go away, and severe cases can damage the colon over time.^[1]

Epidemiology

Colitis is a common condition that appears to be increasing in prevalence worldwide. The disease affects millions of people across different age groups and populations.^[4]

Ulcerative colitis (one specific type of colitis that is a form of inflammatory bowel disease) affects at least 1 in every 227 people in the United Kingdom, which amounts to around 296,000 individuals. In the United States, it is estimated that about one million Americans are living with ulcerative colitis, making it the most common form of inflammatory bowel disease.^[2][5]

While colitis can develop at any age, ulcerative colitis is most often diagnosed in people between 15 and 25 years old. However, the condition can strike at any stage of life, and most people are diagnosed before the age of 30.^[2][5]

The condition shows interesting patterns across different ethnic groups. Ulcerative colitis is more common in white people of European descent, especially those descended from Ashkenazi Jewish communities, as well as in Black people. The condition is rarer in people from Asian backgrounds, although the reasons for these differences are not fully understood. Both men and women appear to be equally affected by ulcerative colitis.^[2][5]

Causes

The causes of colitis vary significantly depending on the specific type a person has. Understanding the root cause is essential for determining the right treatment approach.^[1]

Infectious colitis is caused by viral, parasitic, or bacterial infections. The most common bacterial culprits are Salmonella and E. coli, though other organisms like Campylobacter jejuni, Shigella, Mycobacterium tuberculosis, and parasites such as Entamoeba histolytica can also cause infectious colitis. Viruses like cytomegalovirus may trigger colitis as well. Most people contract infectious colitis from eating or drinking contaminated food or water.^[1][4]

Pseudomembranous colitis results from a specific bacterium known as C. diff (Clostridioides difficile). This organism already lives in the intestines naturally, but certain antibiotics can kill off other bacteria that normally keep C. diff under control, allowing it to overgrow and cause inflammation.^[1]

Allergic colitis primarily affects babies who drink breastmilk. It’s caused by an allergy to the protein in cow’s milk, which can pass through breast milk to the infant.^[1]

Ischemic colitis occurs when the intestines aren’t getting enough blood. A blockage in the blood vessels, such as a blood clot or atherosclerosis (a buildup of fatty deposits in arteries), prevents adequate blood flow to parts of the colon.^[1]

Inflammatory bowel diseases (IBD) are a group of conditions that cause chronic, recurring inflammation in the colon. This category includes ulcerative colitis, microscopic colitis, and Crohn’s disease. Experts believe these are a type of autoimmune disease, which means they cause the immune system to malfunction and attack the body’s own tissue. The exact cause of ulcerative colitis is unknown, but it may involve an abnormal immune response against some microorganism in which the body’s tissues are also attacked. Genetics might also play a role, as having a first-degree relative with the condition increases risk. Many experts think it’s a combination of genetic and environmental factors.^[1][2]

Radiation colitis is a side effect of radiation therapy, which is a treatment for certain types of cancer affecting organs near the colon.^[1]

Diversion colitis is a side effect that can occur in people who’ve had a colostomy (surgery that creates an opening in the abdomen for waste to exit). Experts believe it happens when the part of the colon that’s not being used is deprived of certain nutrients.^[1]

Risk Factors

Several factors can increase a person’s likelihood of developing colitis, though these vary by the type of colitis.

For inflammatory bowel diseases like ulcerative colitis, genetics play an important role. People with a first-degree relative who has the condition are at higher risk. Age is also a factor, with most cases diagnosed before age 30, though the disease can appear at any stage of life.^[2]

Ethnicity influences risk as well. Whites have the highest risk, especially those of Ashkenazi Jewish descent, and Black individuals also have elevated risk. The condition is less common among people of Asian backgrounds.^[2]

For infectious colitis, the main risk factor is consuming contaminated food or water. Poor food handling, inadequate cooking, or drinking from contaminated water sources can expose people to harmful bacteria, viruses, or parasites.^[1]

Taking certain antibiotics increases the risk of pseudomembranous colitis caused by C. diff, as these medications can disrupt the natural balance of bacteria in the intestines.^[1]

People with poor blood flow to the intestines due to conditions like atherosclerosis or blood clots are at risk for ischemic colitis. Those undergoing radiation therapy for cancer near the colon face an increased risk of radiation colitis. Individuals who have had colostomy surgery may develop diversion colitis.^[1]

Symptoms

The symptoms of colitis can vary in severity from mild to severe, depending on how much of the colon is affected and how badly the area is damaged. Symptoms usually come in waves and can range from periods with no symptoms at all to times when symptoms are very troublesome.^[1][3]

Common symptoms that people with colitis experience include abdominal pain, which can be sharp or cramping. Many people feel bloated and have a persistent feeling that they need to have a bowel movement, even when their bowels are empty. This sensation can be urgent and uncomfortable.^[1]

Watery diarrhea is a hallmark symptom of colitis. The stool may contain mucus or blood, which occurs because ulcers in the colon’s lining bleed. Seeing blood or mucus in the stool is particularly common with ulcerative colitis and can be alarming, though it’s a direct result of the inflammation and ulceration in the colon.^[1][3]

Many people with colitis experience loss of appetite, which can lead to unintended weight loss. Fever may develop, particularly during flare-ups when inflammation is more severe. Extreme tiredness, or fatigue, is another common complaint that can significantly affect a person’s ability to carry out daily activities.^[1]

People with ulcerative colitis may also experience stomach cramping with bowel movements and an urgent need to empty their bowels. In some cases, symptoms extend beyond the digestive system. These extra-intestinal symptoms can include painful and swollen joints (arthritis), mouth ulcers, swollen fat under the skin causing bumps and patches, irritated and red eyes, and problems with bones such as osteoporosis.^[3][5]

A rare and severe form of ulcerative colitis, called fulminant ulcerative colitis, causes extremely severe symptoms that require urgent medical treatment. This condition represents a medical emergency and needs immediate care.^[3]

Complications

Complications of colitis usually result from severe, long-term inflammation. These complications can be serious and sometimes life-threatening, requiring immediate medical attention.^[1]

Perforation occurs when chronic inflammation weakens the colon walls, making them more likely to rupture. An ulcer in the colon may wear a hole all the way through the lining of the colon. When this happens, bacteria from the colon can leak into the abdominal cavity or enter the bloodstream, causing a serious infection that can lead to septicemia (blood poisoning).^[1][9]

Toxic megacolon is a dangerous complication where severe inflammation causes the muscles in the colon to stop working properly. Food and gas build up in the colon, causing it to widen or stretch beyond its normal size. This widening increases the risk of rupture, which can be life-threatening. When inflammation spreads to the deeper tissues of the intestines, it can cause inflammation so severe that the colon stops functioning entirely.^[1][3]

People with long-term colitis face an increased risk of developing colon cancer. Long-term inflammation in the colon can sometimes lead to changes in the colon wall that become cancerous over time. This is particularly true for those who have had ulcerative colitis for more than ten years.^[1][9]

Severe bleeding from the rectum can occur when ulcers cause significant amounts of blood to pass during bowel movements. Severe dehydration can result from the colon’s reduced ability to absorb water combined with fluid loss during frequent trips to the bathroom.^[3]

In children with colitis, complications may include poor growth and development, a condition known as failure to thrive. The steroid medicines used to treat ulcerative colitis can cause weakening of the bones (osteoporosis) as a side effect, adding another layer of concern for long-term management.^[5]

Prevention

Preventing colitis depends largely on the type. For infectious colitis, the most important preventive measures involve food and water safety. Practicing good hygiene, thoroughly cooking food, washing hands before preparing or eating food, and avoiding contaminated water sources can significantly reduce the risk of developing infectious colitis.^[1]

For inflammatory bowel diseases like ulcerative colitis, there is no guaranteed way to prevent the condition since its exact cause involves a complex interaction between genetics, the immune system, and environmental factors. However, some lifestyle changes may help reduce the risk of flare-ups for those already diagnosed.^[2]

Keeping a food diary can help identify which foods might trigger symptoms. By documenting what and when you eat, you can identify problem foods and eliminate them from your diet. However, it’s important not to eliminate entire food groups without speaking to your care team, as you may miss out on essential vitamins and minerals.^[13]

Most people with ulcerative colitis are recommended to follow a healthy, balanced diet and drink plenty of fluids to avoid dehydration and ensure they get all the nutrients they need. While a specific diet is not thought to play a role in causing ulcerative colitis, some people with inflammatory bowel disease may be recommended to make temporary changes to their diet after surgery or to help control symptoms during a flare-up.^[13]

Managing stress may help reduce the frequency of symptoms. Exercise has been proven to reduce stress and boost mood, and relaxation techniques like breathing exercises, meditation, and yoga are good ways to teach yourself to relax. Communication with others, especially those who also have the condition, can help reduce feelings of frustration and isolation.^[13]

Regular screening and monitoring are essential for those with chronic colitis. Staying in close contact with healthcare providers and following their recommendations for screening tests can help catch complications early.^[5]

Pathophysiology

Understanding how colitis affects the body helps explain why symptoms occur and why the condition can be so uncomfortable.

In colitis, inflammation affects the inner lining of the colon. The inflammatory process causes the walls of the colon to weaken and swell. This swelling interferes with the colon’s normal functions, particularly its ability to absorb water and form solid waste. When the colon can’t absorb water properly, the result is watery diarrhea.^[3]

In ulcerative colitis specifically, inflammation spreads upward from the rectum through the colon, leaving no healthy tissue along its path. The inflammation only affects the inner lining of the colon and doesn’t reach through other layers of the intestine wall. However, it causes swelling and ulcers all along its path. These ulcers are open sores in the colon’s lining that can bleed and produce pus, which is why people with ulcerative colitis often see blood and mucus in their stool.^[3]

In inflammatory bowel diseases, experts believe the immune system mistakes harmless bacteria inside the colon as a threat and attacks the tissues of the colon, causing it to become inflamed. This abnormal immune response is what defines these conditions as autoimmune diseases. The body’s defense system, which normally protects against infections, goes wrong and attacks healthy tissue instead.^[5]

In ischemic colitis, the lack of adequate blood flow deprives the colon tissues of oxygen and nutrients, causing cells to die and inflammation to develop. This type of colitis occurs when blood vessels become blocked by clots or narrowed by atherosclerosis.^[1]

In pseudomembranous colitis, when antibiotics kill off the beneficial bacteria that normally keep C. diff under control, this harmful bacterium can multiply rapidly and produce toxins that damage the colon’s lining, leading to inflammation.^[1]

The severity of symptoms depends on how much of the colon is affected and how badly the area is damaged. Complete damage to the lining, as occurs in ulcerative colitis, tends to produce more severe symptoms than inflammation that affects only superficial layers.^[3]

Chronic inflammation can cause long-term changes in the colon. The tissue may become scarred, the walls may weaken, and in severe cases, the colon may stop functioning properly. These changes explain why long-term colitis can lead to serious complications like perforation, toxic megacolon, and an increased risk of cancer.^[1]