Types of Colitis: Everything You Should Know

Colitis is inflammation of the tissue that lines the colon. Colitis is not a condition in itself but rather a sign that another disease process is at work in the body.

There are several different types of colitis, including ulcerative colitis, microscopic colitis, pseudomembranous colitis, ischemic colitis, and colitis caused by an allergic reaction. This article will discuss the different types of colitis and how they differ in their symptoms, diagnostic process, potential causes, and treatment options.

Two physicians discuss an endoscopy photo on a computer screen.

Joos Mind / Photodisc / Getty Images

The colon, or large intestine, is where water and a small number of vitamins and minerals are absorbed from food as it passes through the digestive tract. The colon is a hollow tube with several layers of tissue, all of which can be affected by disease and inflammation.

The six sections of the colon (in order after the small intestine) are the cecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum.

Ulcerative Colitis 

Ulcerative colitis is a form of inflammatory bowel disease (IBD). Symptoms can include diarrhea (often bloody), abdominal pain, weight loss, and an urgent need to use the toilet.

Ulcerative colitis is most often diagnosed in young adults and does not have a cure. It was once thought of as a Western disease, but it is increasingly becoming more common in developing countries.

It’s not known what causes ulcerative colitis. There are over 200 genes that may be associated with the development of IBD. It’s thought that there may be several different pathways to the development of IBD because of the large number of genes involved.

Genetics is not the only part of this process, however, because most people who have the genes associated with IBD never develop the condition.

Environmental factors and the gut microbiome may also factor in to the development of the disease. The gut microbiome is composed of bacteria and other microorganisms that normally live in the gut and help with digestion.

There are several medications available to treat ulcerative colitis. Which drug or combination of drugs is used will depend on the severity and extent of the disease, especially how much of the colon is inflamed. Medications include 5-aminosalicylic acid, biologics, steroids, and immunomodulators.

Lifestyle changes and complementary therapies may also be tried. These can include changing your diet, exercising, taking supplements, and trying acupuncture. Caring for mental health through talk therapy, meditation, mindfulness or other therapies may also be part of your treatment plan.

There are several subtypes of ulcerative colitis, which are defined by the way the disease affects the different parts of the colon.

Ulcerative Proctitis

In this form of ulcerative colitis, it is the rectum that is inflamed. Studies have revealed that about 30% of people with ulcerative colitis are diagnosed with ulcerative proctitis.

Common signs and symptoms include diarrhea, with or without blood, pain in the rectum, and the urgent need to go to the bathroom. However, as many as 10% of people with this form may also experience constipation.

Left-Sided Colitis

This is the most commonly diagnosed form of ulcerative colitis. Left-sided colitis affects about 40% of people who are diagnosed with ulcerative colitis. It’s called “left-sided” because the inflammation is found on the left side of the colon. The symptoms can include bloody diarrhea, weight loss, lack of appetite, and pain on your left side that can be severe.


When inflammation is found throughout the colon, it is called pancolitis. It is diagnosed in about 30% of patients with ulcerative colitis. The symptoms can include bloody diarrhea, weight loss, lack of appetite, abdominal cramping, and abdominal pain that can be severe.

Microscopic Colitis

Microscopic colitis is diagnosed in as many as 20% of people who undergo a colonoscopy to determine the cause of their chronic diarrhea. Women tend to be diagnosed three times as often as men. It also is more common in people over the age of 65.

Unlike ulcerative colitis, microscopic colitis does not cause blood in the stool. The inside of the colon looks normal or near normal in a colonoscopy. Some people with this condition find they need to wake up and move their bowels at night. Weight loss and abdominal pain are also common.

There are two subtypes of microscopic colitis: lymphocytic colitis and collagenous colitis. For diagnosis and treatment, a distinction may not be made between the two forms.

Treatment could include aminosalicylates, bismuth subsalicylate, steroids, or immune-modifying drugs. Patients may need to try a few different drugs to get relief from symptoms. Treatment will also depend on the severity of the symptoms because some medications may have side effects.

The cause is not known, but some of the risk factors are:

  • Abnormal bile acid absorption
  • Autoimmune conditions
  • Bacterial antigens
  • Genetic predisposition
  • Taking medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors, and selective serotonin reuptake inhibitors (SSRIs)
  • Smoking

Lymphocytic Colitis

In lymphocytic colitis, a biopsy of the inside of the colon taken during a colonoscopy for evaluation of diarrhea may show an increased amount of a type of white blood cell called lymphocytes.

Collagenous Colitis

In collagenous colitis, a biopsy taken during a colonoscopy for evaluation of diarrhea may show a thickened collagen layer in the tissue lining the colon.

Pseudomembranous Colitis

In pseudomembranous colitis, the lining of the colon becomes inflamed and forms a yellow-white membrane called a pseudomembrane.

Most often, pseudomembranous colitis occurs due to infection by a bacteria called Clostridioides difficile (C. difficile, or C. diff). But it can also occur from other infections or from taking broad-spectrum antibiotics, or it may be associated with other forms of colitis.

The symptoms of pseudomembranous colitis include:

  • Abdominal cramps or pain
  • Abdominal tenderness
  • Diarrhea 
  • Dehydration
  • Fever
  • Mucus in the stool
  • Nausea

Finding the cause of pseudomembranous colitis is important in treating it. For an infection with C. diff the treatment might be antibiotics.

In some cases, when the infection is severe and the treatment is available, a fecal microbiota transplant could be used. This procedure infuses feces from a donor to restore the bacteria commonly found in the digestive tract.

Rebyota is the first FDA-approved fecal microbiota product to prevent the recurrence of Clostridioides difficile infection (CDI) in individuals 18 years of age and older. It is for use after an individual has completed antibiotic treatment for recurrent CDI.

Some of the risk factors associated with pseudomembranous colitis are:

  • Age over 65 years
  • Antibiotic use
  • Being an inpatient in a hospital or skilled care facility
  • Having a history of with another gastrointestinal disorder 
  • Surgery on the intestines
  • Weakened immune system (such as from receiving chemotherapy)

Various tests, including blood tests, stool cultures, and endoscopy (such as a colonoscopy), might be used to understand what’s causing the pseudomembranous colitis.

Ischemic Colitis

If blood flow to the large intestine is blocked or slowed down, it can cause ischemic colitis. This can happen for many reasons, a few of which are high cholesterol, blood clots, surgery, or the use of cocaine or methamphetamine. This condition can occur in people of any age but is most common in those over age 60.

Some of the risk factors for ischemic colitis include:

  • Age over 60 years
  • Congestive heart failure
  • Diabetes
  • Low blood pressure
  • Medications (although this is rare)
  • Antibiotics
  • Chemotherapy
  • Hormones (such as estrogen)
  • Irritable bowel syndrome (IBS) medication for constipation      
  • Pseudoephedrine use
  • Previous surgery on the aorta

Ischemic colitis can come on suddenly, but more often the condition develops over a period of time. In milder cases, treatment in the hospital might include antibiotics, a liquid diet, intravenous fluids, and pain management.

Medications that treat blood clots may also be used. For severe cases, surgery on the colon to remove any tissue that has died might be needed.

Allergic Colitis in Infants

Allergic colitis is a condition that can occur in some infants who are breastfeeding. The only symptom that’s usually found is blood in the stool.

This condition may result from a food allergy, but the cause is not well understood. Tests such as endoscopy aren’t usually done but the diagnosis is based on the occurrence of bloody stools.

The bloody stools normally resolve on their own, but the possibility of a food allergy should be looked into. This includes removing foods from the breastfeeding parent’s diet. Usually this begins with removing dairy products for several weeks and seeing if that makes any difference.

Other foods that commonly cause allergies might also be stopped if the bloody stools don’t improve. In some cases, a special formula might be recommended for feeding.


The first step in making a diagnosis will be reviewing symptoms. A doctor will often ask about stools (how often you defecate and if there is any blood) and a description of any abdominal pain. There may also be questions about family history, diet, and current medications.

Tests might be needed to discover the source of the symptoms. These can include:

  • Barium enema: This type of X-ray uses barium to highlight potential issues in the colon.
  • Blood tests: A blood test won’t be used to diagnose colitis, but it can look for an infection or determine the reason for significant blood loss.
  • Colonoscopy: A long tube with a light and a camera on the end is inserted into the anus and moved up the colon.
  • Computed tomography (CT) scan: This computerized X-ray image can provide a view into the structures in the abdomen.
  • Flexible sigmoidoscopy: A tube is inserted into the anus to see the last section of the colon.
  • Magnetic resonance imaging (MRI): This scan can take detailed images of the abdomen using a magnet field and computer-generated radio waves.
  • Stool tests: Stool may be collected and tested for bacterial infections, parasites, or the presence of blood.
  • Ultrasound: This noninvasive test uses sound waves to visualize the contents of the abdomen.


Colitis is inflammation of the colon. Types include ulcerative colitis, microscopic colitis, pseudomembranous colitis, ischemic colitis, and allergic colitis. Each type of colitis varies in its diagnostic process, causes, and treatment.

Frequently Asked Questions

  • What foods are safest to eat if I have colitis?

    Diet can be an important part of the treatment for colitis. A physician or dietitian will be the best source of information on diet, especially for chronic causes of colitis, such as ulcerative colitis.

    The goal should be eating a healthful diet that includes fruits and vegetables as soon as possible. In the short term, try eating lower-fiber foods and avoiding any foods that may worsen diarrhea or cause pain.

  • Are autoimmune diseases associated with colitis?

    There are a variety of causes of colitis, most of which are not connected to autoimmune or immune-mediated conditions.

    Ulcerative colitis, however, is an immune-mediated disease, and it has been associated with other conditions such as arthritis and psoriasis. It is important to get ulcerative colitis treated and keep it under control in order to avoid potential complications or catch unavoidable ones early.

  • Is colitis contagious?

    Sometimes. Colitis that’s caused by an infection might be contagious through the fecal-oral route. Colitis that is caused by medications, an immune-mediated condition, or an allergy is not contagious.

    This is one more reason why it’s important to get blood in the stool diagnosed and treated promptly. 

  • How is colitis different from Crohn’s disease?

    Colitis is a sign of disease. Both ulcerative colitis and Crohn’s disease are forms of IBD. Crohn’s disease may cause inflammation throughout the digestive system, while ulcerative colitis causes inflammation only in the colon.

    Also, Crohn’s disease can affect all the layers of the colon, while ulcerative colitis only affects the inner layer. Both conditions are not curable and require lifelong treatment.

11 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.
  1. Fumery M, Singh S, Dulai PS, Gower-Rousseau C, Peyrin-Biroulet L, Sandborn WJ. Natural history of adult ulcerative colitis in population-based cohorts: A systematic review. Clin Gastroenterol Hepatol. 2018;16(3):343-356.e3. doi:10.1016/j.cgh.2017.06.016

  2. Guan Q. A comprehensive review and update on the pathogenesis of inflammatory bowel disease. J Immunol Res. 2019 Dec 1;2019:7247238. doi:10.1155/2019/7247238

  3. Ungaro R, Mehandru S, Allen PB, Peyrin-Biroulet L, Colombel JF. Ulcerative colitisLancet. 2017;389(10080):1756-1770. doi:10.1016/S0140-6736(16)32126-2

  4. Townsend T, Campbell F, O'Toole P, Probert C. Microscopic colitis: diagnosis and managementGastroenterol. 2019;10(4):388-393. doi:10.1136/flgastro-2018-101040

  5. Park T, Cave D, Marshall C. Microscopic colitis: A review of etiology, treatment and refractory disease. World J Gastroenterol. 2015;21(29):8804–8810. doi:10.3748/wjg.v21.i29.8804

  6. Madisch A, Hellmig S, Schreiber S, Bethke B, Stolte M, Miehlke S. Allelic variation of the matrix metalloproteinase-9 gene is associated with collagenous colitis. Inflamm Bowel Dis. 2011;17:2295-8. doi:10.1002/ibd.21640

  7. Farooq PD, Urrunaga NH, Tang DM, von Rosenvinge EC. Pseudomembranous colitisDis Mon. 2015;61(5):181-206. doi:10.1016/j.disamonth.2015.01.006

  8. Food and Drug Administration. FDA approves first fecal microbiota product.

  9. FitzGerald JF, Hernandez Iii LO. Ischemic colitisClin Colon Rectal Surg. 2015;28(2):93-98. doi:10.1055/s-0035-1549099

  10. Xu Y, Xiong L, Li Y, Jiang X, Xiong Z. Diagnostic methods and drug therapies in patients with ischemic colitis. Int J Colorectal Dis. 2021;36(1):47-56. doi:10.1007/s00384-020-03739-z

  11. Molnár K, Pintér P, Győrffy H, Cseh A, Müller KE, Arató A, Veres G. Characteristics of allergic colitis in breast-fed infants in the absence of cow's milk allergy. World J Gastroenterol. 2013;19(24):3824-30. doi:10.3748/wjg.v19.i24.3824

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.