Reviewed on 7/22/2022

Things to Know About Colitis

Inflammation of the colon (Colitis)

6 common causes of colitis include infections, ischemic colitis, IBD, microscopic colitis, chemical colitis, and medication-associated colitis.

  • Colitis is a term used to describe inflammation of the colon.
  • There are many causes of colitis, for example, infections (food poisoning from E. coli, Salmonella), poor blood supply, and autoimmune reactions.
  • Symptoms of colitis include:
  • Individuals with colitis may have mild, moderate, or severe colitis.
  • Types of colitis include microscopic colitis, C. diff colitis, infectious colitis, ischemic colitis, Crohn’s disease and ulcerative colitis (one type of inflammatory bowel disease), and chemical colitis.
  • Diagnosis of colitis is made by patient history, physical examination, laboratory tests, colonoscopy, and imaging tests.
  • Treatment for colitis depends on the specific type of colitis.

What Is Colitis?

Colitis is an inflammation of the colon, also known as the large intestine. While there are many causes of colitis including:

  • Infections
  • Poor blood supply (ischemia)
  • Autoimmune reactions

They share common symptoms of abdominal pain and diarrhea.

What Are the Symptoms of Colitis?

Symptoms of colitis will depend upon the type of colitis a person has, but in general, colitis most often is associated with:

  • Abdominal pain 
  • Diarrhea

Other symptoms of colitis that may or may not be present include:

  • Blood in the stools, depending on the underlying disease. Diarrhea can sometimes cause hemorrhoids, which can bleed. However, blood with a bowel movement is not normal and the affected person should contact their healthcare professional or seek other medical care.
  • Constant urge to have a bowel movement (tenesmus).
  • Abdominal pain may come in waves, building to diarrhea, and then waning.
  • Constant pain.
  • Fever, chills, and other signs of infection and inflammation may be present depending on the cause of colitis.

What Are the Types of Colitis?

There are many types of colitis. The most common include:

6 Common Causes of Colitis

Inflammation of the colon can be caused by a variety of illnesses and infections. Some of the most common causes are discussed in the next few sections.

1. Infectious Colitis

  • Viruses and bacteria can cause colon infections. Most are food-borne illnesses or "food poisoning." Common bacterial causes of food borne infection include Shigella, E Coli, Salmonella and Campylobacter. These infections may cause bloody diarrhea and can result in significant dehydration.
  • Parasite infections such as giardia also can cause significant diarrhea. The parasite can enter the body when infected water is swallowed. The source may be from recreational water such as rivers, lakes, and swimming pools. It also may be contaminated water from a well or cistern.
  • Pseudomembranous colitis is caused by the bacteria Clostridium difficile (C. difficile). This disorder is often seen in patients who have recently been taking antibiotics for an infection or have been admitted to the hospital. The antibiotic alters the normal bacteria present in the colon that helps with digestion and allows an overgrowth of the Clostridium bacteria. Clostridium bacteria produce a toxin that causes diarrhea. This is an infection, and often there is a fever present. The diarrhea is usually not bloody.

2. Ischemic Colitis

  • The arteries that supply blood to the colon are like any other artery in the body. They have the potential to become narrow due to atherosclerosis (just like blood vessels in the heart, which can cause angina, or narrowed vessels in the brain can cause a stroke). When these arteries become narrow, the colon may lose its blood supply and become inflamed.
  • The colon can also lose its blood supply for mechanical reasons. A couple of examples include volvulus, where the bowel twists on itself, or an incarcerated hernia, where a portion of the colon gets trapped in an outpouching of the abdominal wall, which prevents blood from flowing to the affected portion.
  • In individuals who are at risk for decreased blood flow to the colon, ischemic colitis can occur if the blood pressure falls. This may occur with dehydration, anemia, or shock.
  • Ischemia or lack of blood supply causes significant pain, fever, and bloody bowel movements.
  • Blood clots can also travel or embolize to block an artery and decrease blood flow to the bowel. Individuals who have the common heart rhythm disturbance, atrial fibrillation, are at risk of forming small clots in the heart, which break off and block the blood supply to the bowel. This is the same mechanism that can cause a stroke or TIA (transient ischemic attack) if the blockage occurs in an artery that supplies the brain.

3. Inflammatory Bowel Disease (IBD) and Colitis

There are two types of inflammatory bowel disease; 1) ulcerative colitis, and 2) Crohn's disease.

  • Ulcerative colitis is thought to be an autoimmune illness in which the body's immune system attacks the colon and causes inflammation. Ulcerative colitis begins in the rectum and may gradually spread throughout the colon. The signs and symptoms include abdominal pain and bloody bowel movements.
  • Crohn's disease may involve any part of the digestive tract from the mouth, esophagus, and stomach, through to the small and large intestine all the way to the rectum and anus. It often involves skin lesions, which are diseased areas interspersed with healthy areas of tissue.

4. Microscopic Colitis

  • This includes two diseases: collagenous colitis and lymphocytic colitis. In these diseases, the inflammation is caused when the colon wall becomes engorged with either collagen or lymphocytes. Watery, non-bloody diarrhea is the most common symptom.
  • This is an uncommon illness that is seen more frequently in older women. The cause is unknown but an autoimmune potential may exist.

5. Chemical Colitis

  • If chemicals are instilled into the colon, inflammation and damage can occur. One of the complications of an enema is inflammation of the mucosal lining of the colon caused by harsh chemicals.

6. Medication-Associated Colitis

  • Colitis can be caused by some over-the-counter and prescription medications such as NSAIDs (nonsteroidal anti-inflammatory drugs), mycophenolate, ipilimumab, and retinoic acid.

When to Seek Medical Care for Colitis

Diarrhea is a common symptom of colitis, and most episodes resolve in a matter of hours.

Medical care should be sought if any of the following symptoms occur:

  • Persistent diarrhea
  • Dehydration (symptoms of dehydration include lightheadedness; weakness; decreased urination; dry mouth, eyes, and skin)
  • Fever
  • Significant abdominal pain
  • Blood in the bowel movement

Which Type of Doctor Treats Colitis?

Gastroenterologists are the medical specialists that treat diseases of the gastrointestinal organs such as colitis.

  • In some cases, colitis may be managed by primary care specialists or internal medicine specialists.
  • Depending on the type of colitis, other specialists may be involved in the treatment, including:
    • Infectious disease specialists or surgeons
    • Pediatricians or pediatric gastroenterologists are involved in the care of infants, children, and teens with colitis

What Questions Will My Doctor Ask Me About My Colitis?

Your doctor will perform a physical examination on the patient by taking vital signs and focusing on the abdomen feeling for areas of tenderness, masses, or abnormally enlarged organs.

Your doctor will also take a past medical history to assess the risk factors for peripheral vascular disease (narrowing of the arteries), for example, smoking, high blood pressure, high cholesterol, and diabetes. These risk factors are important in exploring ischemic bowel as the cause for colitis.

Your doctor may ask the patient the following questions:

  • When and what time did the symptoms start?
  • How long does the pain last?
  • How frequent is your diarrhea?
  • Are any other associated symptoms or signs?
  • Have you traveled recently, been on an unusual diet, or used or drank noncommercial water (for example, drinking from a well or river water on a camping trip)? This may assist in the diagnosis of bacterial infections such as Shigella, Campylobacter, or Yersinia or parasite infections such as giardia.
  • Have you recently used antibiotics? Recent use of antibiotics may direct the doctor to consider Clostridium difficile (C Diff) as the cause.
  • Has there been any blood in your stools?

What Exams and Tests Diagnose Colitis?

While unpleasant, the rectal examination is very important. Using a finger, the doctor feels inside the rectum, exploring for any masses or tumors. The color and consistency of stool can be evaluated, and if it is not grossly bloody, can be tested for occult blood (blood that is present but cannot be seen with the naked eye).

Laboratory Tests

The history will assist the health-care professional decide the tests to order and what cultures would be appropriate. Blood tests help assess the stability of the patient, and also explore any potential issues associated with colitis.

  • A complete blood count (CBC) will assess the red blood cell count, the white blood cell count, and the number of platelets.
    • The red blood cell count will help define the amount of bleeding.
    • White blood cell counts elevate when the body is undergoing physical (exercise), physiological, or emotional stress.
    • Platelets help blood to clot, so knowing the platelet number in a patient with bleeding may be useful.
  • Electrolyte abnormalities can occur with diarrhea. Low sodium (hyponatremia) and low potassium (hypokalemia) levels may occur and cause symptoms far removed from the initial colitis signs and symptoms.
  • Kidney function may be assessed by measuring the BUN (blood urea nitrogen) and creatinine levels.
  • Erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) are nonspecific test of inflammation in the body.
  • Stool samples may be collected for culture, looking for infection as the cause of colitis


If a specific cause of colitis is not readily apparent, then colonoscopy may be considered. A gastroenterologist will insert a long flexible fiberoptic camera into the anus and examine the full length of the colon. The appearance of the colon by itself may be enough to make the diagnosis. Biopsies (small pieces of tissue) may be taken from the lining of the colon and examined by a pathologist (a medical doctor specializing in the diagnosis of tissues) to help confirm the diagnosis. Microscopic colitis (lymphocytic and collagenous) can only be diagnosed with biopsy of the affected area.

Colonoscopy is an essential cancer screening test and is especially important for those patients who have had blood in their stool that cannot be explained by another diagnosis.


Computerized tomography (CT) may be used to image the colon and the rest of the abdomen. Different types of colitis have distinctive patterns that may help a radiologist recognize a specific diagnosis. A CT scan may be ordered urgently if the history and physical examination performed by the health-care professional leads to concern that an urgent or emergent problem exists that might require surgery. On occasion, a barium enema or other imaging tests such as ultrasound may be used to evaluate the anatomy of the colon and assist in diagnosis.

What Is the Treatment for Colitis?

The definitive treatment of colitis depends upon the cause. Many cases require little more than symptomatic care, including clear fluids to rest the bowel and medications to control pain. Some patients become acutely ill and will need intravenous (IV) fluids and other interventions to treat their illness.

  • Infections: Depending on the cause, infections that cause diarrhea and colitis may or may not require antibiotics. Viral infections resolve with the supportive care of fluids and time. Some bacterial infections like Salmonella also do not need antibiotic therapy; the body is able to get rid of the infection on its own. However, other bacterial infections like Clostridium difficile always require treatment with antibiotics.
  • Ischemic colitis: Treatment of ischemic colitis is initially supportive, using intravenous fluids to rest the bowel and prevent dehydration. If adequate blood supply to the bowel isn't restored, surgery may be required to remove parts of the bowel that have lost blood supply and become necrotic (tissue that has died).
  • Inflammatory bowel disease (IBD): Inflammatory bowel diseases (IBDs) like ulcerative colitis and Crohn's disease, are often controlled by a combination of medications that are used in a step-wise approach. Initially, anti-inflammatory medications are used, and if these are less than successful, medications that suppress the immune system can be added. In the most severe cases, surgery may be required to remove all or parts of the colon and small intestine.
  • Diarrhea and abdominal pain: Most causes of colitis present with diarrhea and crampy abdominal pain. These symptoms are also found with mild illnesses like viral enterocolitis (inflammation of the small intestine and colon). Initial treatment at home may include a clear fluid diet for 24 hours, rest, and acetaminophen (Tylenol) or the NSAID ibuprofen (Advil, Motrin, etc.) as needed for pain. Often symptoms resolve quickly and no further care is needed. Loperamide (Imodium) is an effective medicine to control diarrhea if there is no blood or fever present.

Is There a Colitis Diet?


  • A clear fluid diet may be the best way to treat the diarrhea associated with colitis. Clear fluids are absorbed in the stomach and no waste products are delivered to the colon, allowing it to rest. Clear fluids without carbonation (bubbles) include anything that one can see through, and also includes popsicles and Jell-O.
  • Depending on the cause of colitis, there may be some foods that can be tolerated and others that make the symptoms worse or produce “flares.” Keep a food diary to help identify and eliminate trigger foods, and identify and eat more foods that soothe or calm the colon.
  • Individuals with certain food intolerance may need to avoid whole groups of foods. Those with lactose intolerance should not eat foods containing dairy products including milk, cheese, yogurt, and ice cream. Those with celiac disease need to avoid gluten containing foods.
  • Individuals with inflammatory bowel disease (ulcerative colitis and Crohn's Disease) may want to limit exposure to fatty, greasy, and fried foods, high fiber foods (seeds, nuts, corn), and dairy products.


  • Hydration: Adequate hydration is important because an individual can lose a significant amount of fluid with each diarrheal bowel movement. Aside from the daily fluid requirements, this excess loss needs to be replaced, otherwise dehydration will occur and potentially worsen the symptoms of abdominal pain and cramping.
  • IV fluids: Intravenous (IV) fluid may be required, especially if the patient cannot drink enough fluids by mouth. For some illnesses like ischemic colitis, in which blood flow to the bowel is already compromised, adequate hydration is a key element in treatment. Electrolyte replacement may be required in some patients who have significant dehydration.

Can Surgery Cure Colitis?

Surgery may be required for ischemic colitis, Crohn's disease, or ulcerative colitis, depending upon the severity of the illness and the response to more conservative non-surgical treatments.

  • In ulcerative colitis, removal of the colon cures the disease, but the trend is now to try to control inflammation and minimize the need for surgery. Screening colonoscopy is required for patients with ulcerative colitis, since there is an increased potential for developing colon cancer.
  • For some illnesses, the part of the colon that is at risk or damaged is typically removed.

What Follow-Up Care Is Necessary After Being Diagnosed With Colitis?

  • Infectious colitis: Infectious colitis it is an isolated event for most people, and once the symptoms and infection have cleared, no further care is needed.
  • Inflammatory bowel disease: The goal with inflammatory bowel disease becomes symptom control instead of disease cure, since symptoms can occur over the course of a lifetime. Once the initial diagnosis is made, continued care with a primary care doctor and a gastroenterologist will be necessary. A long-term relationship with this treatment team may be able to lessen the frequency and intensity of future disease flare-ups.
  • Ischemic bowel disease: Ischemic colitis does not occur in isolation (meaning there is/are an underlying disease associated with colitis), for example, a person that has poor circulation to the bowel likely has poor circulation elsewhere. Continued monitoring may be necessary to minimize the risk of future episodes. Individuals need to make a lifelong commitment to control high blood pressure (hypertension), high cholesterol, diabetes, and quit smoking.

Can Colitis Be Prevented?

Infectious colitis remains a common illness worldwide, affecting millions daily. The lack of clean drinking water and adequate sanitation are the main causes, leading to thousands of potentially preventable deaths each day. In developed countries, poor hand washing and poor kitchen hygiene allow the potential for infectious colitis. Prevention lies in cleanliness.

Inflammatory bowel diseases are difficult to prevent at the present time. The likely causes are heredity and perhaps an abnormal auto-immune response to an unknown stimulus in the body.

Since ischemic colitis is caused by narrowing of the blood vessels to the bowel, decreasing the risks for other types of circulatory problems such as peripheral vascular disease, heart attack, and stroke will also decrease the risk for ischemic colitis. The common risk factors are smoking and poor control of high blood pressure, high cholesterol levels, and diabetes.

What Is the Outlook for a Person With Colitis?

Understanding the cause of specific colitis has allowed for more targeted therapy. For example, observation has replaced surgery to remove the colon as standard therapy for some people with ulcerative colitis, and limiting the use of antibiotics has decreased the number of resistant bacteria that can cause infectious diarrhea.

Worldwide, initiatives to increase access to clean water and adequate hygiene are perhaps the most important way to save lives.

How Much Do You Know about Ulcerative Colitis?

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Reviewed on 7/22/2022
Image Source: BigStock/iStock Peppercorn, MA. MD, et al. Clinical manifestations, diagnosis, and prognosis of ulcerative colitis in adults." UpToDate. March 2020.

J. Larry Jameson, et al. Harrison's Principles of Medicine. McGraw-Hill Professional Publishing Published: July 23rd 2018; Edition: 20.