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What Is Colitis? Common Causes of Colitis

What Is Colitis? Common Causes of Colitis

Colitis refers to the inflammation of the lining of the colon. Many different conditions can cause this to happen.

The most common type of colitis is ulcerative colitis. With this type, ulcers or sores develop in the stomach. The inflammation extends from the rectum along the inner lining of the colon.

Colitis refers to the inner lining of the colon becoming inflamed. Colitis can be a symptom of a disease that affects other parts of the body, which causes fevers, chills, fatigue and dehydration.

Types and causes of colitis may differ, but most symptoms overlap. How the condition affects an individual varies from person to person.

What is Colitis?

Colitis is an inflammation of the lining of the colon. Infection, loss of blood supply in the colon, Inflammatory Bowel Disease (IBD) and invasion of the colon wall with collagen or lymphocytic white blood cells are all possible causes of an inflamed colon. Some of the common symptoms of this condition include abdominal cramping, frequent loose stools or persistent diarrhea, loss of control of bowel function, fever, and weight loss. There are many potential causes of colon inflammation, and its treatment typically depends on the cause.

Some forms of colitis might be caused by infection through bacteria, certain viruses and some parasites. For example, it might be caused by exposure to salmonella bacteria or an amoebic infection. Antibiotics or anti-parasitic medication typically are required to treat colon inflammation that has any of these causes.

Viruses such as rotavirus and norovirus also can cause colon inflammation and can result in dehydration, particularly in people who are very young or very old. Rest and increased fluid intake are often prescribed in these cases. If a person becomes severely dehydrated, however, he or she might need care in a hospital to receive intravenous fluids.

What Are the Symptoms of Colitis?

The main symptom of microscopic colitis is chronic diarrhea. This disease is referred to as microscopic because inflammation cannot be seen unless a tissue sample is examined under a microscope.

On the other hand, ischemic colitis symptoms are typically more sudden, rather than gradual.

In addition to diarrhea, symptoms include:

  • Stomach pain, tenderness or cramping
  • Nausea
  • Red- or maroon-colored blood in your stool or, at times, passage of blood alone without stool
  • An urgent need to move your bowels

Ulcerative colitis symptoms are usually mild to moderate. Typically, doctors diagnose ulcerative colitis based on the location where symptoms are felt in the colon.

Depending on where colon inflammation occurs, you may experience the following symptoms:

  • Abdominal pain or cramping
  • Diarrhea, accompanied with blood or pus
  • Rectal pain and bleeding
  • Weight loss
  • Fatigue
  • Fever

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

  • Blood in the bowel movement may be present 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 health-care professional or seek other medical care.
  • The constant urge to have a bowel movement (tenesmus).
  • The abdominal pain may come in waves, building to diarrhea, and then waning.
  • There may be a constant pain.
  • Fever, chills, and other signs of infection and inflammation may be present depending upon the cause of colitis.

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.

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.

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.

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 has skip lesions, that is diseased areas are interspersed with healthy areas of tissue.

Microscopic Colitis

  • Two diseases make up this group of colon inflammation, 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.

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.

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.

Different Types of Colitis

There are many different forms of colitis, including:

  • Ulcerative colitis
  • Crohn’s colitis
  • Diversion colitis
  • Ischemic colitis
  • Infectious colitis
  • Fulminant colitis
  • Collagenous colitis
  • Chemical colitis
  • Microscopic colitis
  • Lymphocytic colitis
  • Atypical colitis

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.


The treatment of colitis depends upon the cause.

For undiagnosed or uncontrolled colitis, the initial therapy (regardless of the cause) is to stabilize the patient’s vital signs and help control pain if needed. Rehydration may be accomplished by mouth. However, for those patients who are markedly dry, who are unable to tolerate fluids by mouth, or have electrolyte abnormalities, intravenous fluids may be required.

Medications are often used to control IBD and the choice of medication is tailored to the individual patient.

Antibiotics are not commonly used unless a specific bacteria is isolated and treatment is known to shorten the course of the infection.

Over-the-counter medications to treat diarrhea should be used with caution, especially if abdominal pain and fever are present. It is always wise to check with a care provider or pharmacist prior to taking antidiarrheal medications.

Surgery is usually not a treatment option for most causes of colitis.

What foods help soothe colitis flares?

Colitis often is associated with diarrhea, and the body can lose significant amounts of fluid with each episode of diarrhea. Moreover, the colon is inflamed, and it is important to try to “rest” it. Since clear fluids tend to be absorbed mostly in the stomach and small intestine, initially avoiding solid foods and promoting a clear fluid diet may be of help in rehydrating the body and resting the colon.

Changing your diet to reduce symptoms or flares may help soothe the symptoms of the disease, but there is no cure for some forms of colitis.

What foods should I avoid if I have colitis?

Depending on the cause, some people with colitis may find that certain foods bring on or make their symptoms worse. Keeping a food diary may be helpful and then avoid foods that may be associated with worsening symptoms.

The Crohn’s & Colitis Foundation of America recommends avoiding the following foods if you have colitis:

  • Greasy or fried foods
  • Milk or products containing milk
  • Certain high-fiber foods like popcorn, seeds, nuts, and corn

People who are lactose intolerant should avoid dairy products containing lactose. There are a variety of companies (for example, Lactaid and Green Valley Organics) that offer lactose-free products such as milk, yogurt, ice cream, and cottage cheese.


Many people have found that one or more of the following foods have triggered their symptoms:

  • Alcohol
  • Caffeine
  • Carbonated beverages
  • Dairy products (if lactose intolerant)
  • Dried beans, peas, legumes, dried fruits or berries
  • Fruits with pulp or seeds
  • Foods containing sulfur or sulfate
  • Foods high in fiber (including whole-grained products)
  • Hot sauces and spicy foods
  • Meats
  • Nuts and crunchy nut butters
  • Popcorn
  • Products containing sorbitol (sugar-free gum and candies)
  • Raw vegetables
  • Refined sugar
  • Seeds

Read more Ulcerative Colitis Diet What Foods Should You Eat and Avoid

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