Colitis is an inflammation of the lining of the colon. A person with colitis will typically experience abdominal pain, discomfort, and diarrhea.

People with colitis may experience mild chronic pain or severe and sudden pain. There are different types of colitis, and many have overlapping symptoms.

This article looks at colitis, different types of colitis, causes, symptoms, and treatments.

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Colitis is an inflammation of the colon’s lining. The large intestine can become inflamed for several different reasons. The most common causes typically include infection, such as:

Both Crohn’s disease and ulcerative colitis form the two major types of IBD.

This condition typically affects people between 15–35 years of age, and then there is a second peak of the condition in people between 60–70 years of age.

Colitis is often chronic, and there is no known cure. However, a person can receive treatment for the condition and effectively manage it.

There are several types of colitis. These include:

Ulcerative colitis is a chronic condition in which the lining of the large intestine (the colon or large bowel) and the rectum become inflamed.

Small sores or ulcers can develop on the lining of the colon, which can bleed and produce pus.


Symptoms of ulcerative colitis may include:


Doctors consider ulcerative colitis to be an autoimmune condition.

Research suggests that an atypical immune response occurs. This response is triggered by an interaction between bacteria in the colon and the body’s immune system, which then attacks the colon’s tissue. This attack causes inflammation.

It is not clear what causes the immune system to behave this way. However, experts believe several factors, including genetics and environmental factors, may play a role.


Treatment may involve taking medication, such as:

A person can usually treat flare-ups at home, but severe flare-ups may require hospitalization.

In extreme flares, a person may need surgery to remove parts of their colon.

In pseudomembranous colitis, the colon becomes inflamed due to an overgrowth of a bacteria called Clostridioides difficile (C. difficile). This may occur due to a person having a weakened immune system or from an imbalance in gut bacteria due to recent antibiotic use.


Symptoms of pseudomembranous colitis include:

  • frequent watery diarrhea
  • abdominal cramps
  • fever
  • bloody stools
  • urge to have a bowel movement


An overgrowth of C. difficile bacteria usually happens due to a disruption of typical intestinal bacteria following a course of antibiotics. Certain strains of C. difficile are resistant to some antibiotics, may be able to overgrow, and can cause inflammation and bleeding.


A person with this condition will need to stop taking any drugs that are causing the issue. A doctor may prescribe medications such as vancomycin or fidaxomicin (Dificid).

The person may also receive intravenous (IV) fluids. In severe cases, doctors may need to perform a colectomy.

Fecal microbiota transplant is a new treatment option that effectively treats recurring infections.

Microscopic colitis is a condition in which the immune system malfunctions and causes inflammation in the lining of the colon.

People of any age can develop the condition, but it is more common in women and older adults.


Symptoms may include:

  • persistent watery diarrhea
  • nighttime diarrhea
  • bloating and gas
  • urgent need to have bowel movement
  • weight loss
  • fatigue
  • cramping and pain in the abdomen


It is not certain what causes microscopic colitis, but doctors believe a combination of genetics and atypical immune system responses may be the reason.

A person should speak with their doctor about the medications they are taking, as some medications may trigger microscopic colitis.

Medications that may cause this type of colitis include:


Doctors may prescribe the following medications for microscopic colitis:

  • corticosteroids
  • biologics
  • bile acid binders
  • antidiarrheal medications
  • aminosalicylates
  • immunosuppressants

Ischemic colitis occurs because of reduced blood flow to the colon.

Experts generally associate it with older people who have underlying cardiovascular conditions. However, young people can develop the condition.


Symptoms may include:

  • pain and cramping, typically on the left side of the abdomen
  • nausea
  • bloody diarrhea
  • vomiting
  • tender stomach
  • pain after eating
  • an urgent need for a bowel movement


Ischemic colitis is caused by reduced blood flow to the colon. This can happen for various reasons, such as hardened arteries in people with peripheral vascular disease or coronary artery disease.

Other factors that may cause reduced blood flow include:

  • surgical procedures that involve the colon, heart, or blood vessels
  • low blood pressure
  • blood clots in the arteries that lead to the colon
  • conditions that affect the blood, such as anemia
  • use of methamphetamines or cocaine
  • bowel obstructions due to hernias, tumors, or scar tissue


Treatment for ischemic colitis depends on the severity of the condition. A doctor may treat mild cases with:

  • IV fluid to prevent dehydration
  • broad-spectrum antibiotics to prevent infection
  • medication to relieve pain

A doctor may also treat underlying conditions that contribute to the condition. They may advise against medications that cause narrowing of the blood vessels.

If the condition is severe or acute, a doctor will treat it as an emergency. They may:

  • prescribe medications to widen narrowed arteries or treat blood clots
  • recommend surgery

About 20% of people with ischemic colitis require some surgery.

Cytomegalovirus (CMV) colitis is a member of the human herpesvirus family.

CMV colitis occurs most commonly in immunocompromised people, or individuals with a suppressed immune system. However, it can also occur in healthy people without immunodeficiency. These people usually have a median age of 68 years.


For some people, CMV colitis does not usually present any symptoms or it may be a self-limited disease, meaning it goes away on its own.

However, other people with CMV colitis may show nonspecific symptoms, including:

  • diarrhea
  • abdominal pain
  • fever
  • rectal bleeding
  • weight loss


CMV colitis occurs most commonly in immunocompromised people, including people with:

Further research has identified several risk factors associated with CMV colitis in people with typical immune responses, also known as immunocompetent. These risk factors include:

  • renal diseases
  • people on hemodialysis
  • neurological disorders
  • people in an intensive care unit


The majority of people with CMV colitis who are immunocompetent may need no treatment with antiviral medications.

Antiviral treatment may be considered by doctors in select immunocompetent people based on their age and medical history. Further research is required to determine whether the treatment of CMV colitis with antiviral agents is effective.

Allergic colitis may occur when a baby’s immune system overreacts to the proteins found in cow’s milk. Other allergens such as soy can also cause a similar reaction. This reaction leads to inflammation in the colon.

Allergic colitis affects between 2–3% of infants.


Some babies are much more sensitive to milk protein, so they may have more severe symptoms than others.

The symptoms associated with allergic colitis may include:

In the first year of a baby’s life, they go through a period of reflux, or spitting up food. Babies with allergic colitis may have difficulty with reflux.


Allergic colitis is caused by changes to the mother’s immune system during pregnancy and the immaturity of a baby’s own immune system. However, it is not certain why some babies develop the condition and others do not.

Babies who have a family history of food allergies, asthma, or environmental allergies seem to have a slightly higher risk of allergic colitis.


Usually, if an infant has blood in their stool, it is caused by a milk allergy, which is treatable.

Doctors may place breastfeeding people on a dairy-free diet. It can take up to 72 hours for breast milk to become free of milk protein. Alternatively, people can give babies a hypoallergenic formula.

Treating colitis may also lead to an improvement in the reflux, but some of the reflux may not be related to the allergy process.

Colitis is an inflammation in the lining of the colon or large intestine. The lining of the colon can become inflamed for many reasons. The most common cause of colitis is infection. IBD is the most common cause of chronic colitis.

The symptoms of many types of colitis overlap. However, all forms of colitis involve inflammation of the colon lining.

Treatment varies depending on the type and severity of colitis.