Colitis is inflammation of your colon, also known as your large intestine. If you have colitis, you’ll feel discomfort and pain in your abdomen that may be mild and reoccurring over a long period of time, or severe and appearing suddenly.

There are different types of colitis, and treatment varies depending on what type you have.

The types of colitis are categorized by what causes them.

Ulcerative colitis

Ulcerative colitis (UC) is one of two conditions classified as inflammatory bowel disease. The other is Crohn’s disease.

UC is a lifelong disease that produces inflammation and bleeding ulcers within the inner lining of your large intestine. It generally begins in the rectum and spreads to the colon.

UC is the most commonly diagnosed type of colitis. It occurs when the immune system overreacts to bacteria and other substances in the digestive tract, but experts don’t know why this happens. Common types of UC include:

  • proctosigmoiditis, which affects the rectum and lower portion of the colon
  • left-sided colitis, which affects the left side of the colon beginning at the rectum
  • pancolitis, which affects the entire large intestine

Pseudomembranous colitis

Pseudomembranous colitis (PC) occurs from overgrowth of the bacterium Clostridium difficile. This kind of bacteria normally lives in the intestine, but it doesn’t cause problems because it’s balanced by the presence of “good” bacteria.

Certain medications, especially antibiotics, may destroy healthy bacteria. This allows Clostridium difficile to take over, releasing toxins that cause inflammation.

Ischemic colitis

Ischemic colitis (IC) occurs when blood flow to the colon is suddenly cut off or restricted. Blood clots can be a reason for sudden blockage. Atherosclerosis, or buildup of fatty deposits, in the blood vessels that supply the colon is usually the reason for recurrent IC.

This type of colitis is often the result of underlying conditions. These may include:

Although it’s rare, IC may occur as a side effect of taking certain medications.

Microscopic colitis

Microscopic colitis is a medical condition a doctor can only identify by looking at a tissue sample of the colon under a microscope. A doctor will view signs of inflammation, such as lymphocytes, which are a kind of white blood cell.

Doctors sometimes classify microscopic colitis into two categories: lymphocytic and collagenous colitis. Lymphocytic colitis is when a doctor identifies a significant number of lymphocytes. However, the colon tissues and lining are not abnormally thickened.

Collagenous colitis occurs when the colon’s lining becomes thicker than usual due to a buildup of collagen under the outermost layer of tissue. Different theories exist about each microscopic colitis type, but some doctors theorize that both colitis types are different forms of the same condition.

Doctors don’t know exactly what causes microscopic colitis. However, they do know some people are more at risk for the condition. These include:

  • current smokers
  • female gender
  • history of an autoimmune disorder
  • older than age 50

The most common symptoms of microscopic colitis are chronic watery diarrhea, abdominal bloating, and abdominal pain.

Allergic colitis in infants

Allergic colitis is a condition that can occur in infants, usually within the first two months after birth. The condition can cause symptoms in infants that include reflux, excessive spitting up, fussiness, and possible flecks of blood in a baby’s stool.

Doctors don’t know exactly what causes allergic colitis. According to a 2013 study published in the , one of the most popular theories is that infants have an allergic or hypersensitive reaction to certain components in breast milk.

Doctors will often recommend an elimination diet for mom where she slowly stops eating certain foods known to contribute to allergic colitis. Examples include cow’s milk, eggs, and wheat. If baby stops having symptoms, these foods were likely the culprit.

Additional causes

Other causes of colitis include infection from parasites, viruses, and food poisoning from bacteria. You may also develop the condition if your large intestine has been treated with radiation.

Different risk factors are associated with each type of colitis.

You’re more at risk for UC if you:

  • are between the ages of 15 and 30 (most common) or 60 and 80
  • are of Jewish or Caucasian descent
  • have a family member with UC

You’re more at risk for PC if you:

You’re more at risk for IC if you:

Depending on your condition, you may experience one or more of the following symptoms:

  • abdominal pain or cramping
  • bloating in your abdomen
  • weight loss
  • diarrhea with or without blood
  • blood in your stool
  • urgent need to move your bowels
  • chills or fever
  • vomiting

While every person may experience diarrhea from time to time, see a doctor if you have diarrhea that doesn’t seem to be related to an infection, a fever, or any known contaminated foods. Other symptoms that indicate it’s time to see a doctor include:

  • joint pain
  • rashes that have no known cause
  • small amount of blood in stool, such as slightly red-streaked stool
  • stomach pain that keeps coming back
  • unexplained weight loss

Seek immediate medical attention if you see a significant amount of blood in your stool.

If you feel that something isn’t right with your stomach, it’s best to talk to your doctor. Listening to your body is important to staying well.

Your doctor may ask about the frequency of your symptoms and when they first occurred. They’ll perform a thorough physical exam and use diagnostic tests such as:

  • colonoscopy, which involves threading a camera on a flexible tube through the anus to view the rectum and colon
  • sigmoidoscopy, which is similar to a colonoscopy but shows only the rectum and lower colon
  • stool samples
  • abdominal imaging such as MRI or CT scans
  • ultrasound, which is useful depending on the area being scanned
  • barium enema, an X-ray of the colon after it’s injected with barium, which helps make images more visible

Treatments vary by a few factors:

  • type of colitis
  • age
  • overall physical condition

Bowel rest

Limiting what you take in by mouth can be useful, especially if you have IC. Taking fluids and other nutrition intravenously may be necessary during this time.

Medication

Your doctor may prescribe anti-inflammatory medication to treat swelling and pain, and antibiotics to treat infection. Your doctor may also treat you with pain medications or antispasmodic drugs.

Surgery

Surgery to remove part or all of your colon or rectum may be necessary if other treatments don’t work.

Your outlook depends on the type of colitis you have. UC may require lifelong medication therapy unless you have surgery. Other types, such as IC, may improve without surgery. PC generally responds well to antibiotics, but it may reoccur.

In all cases, early detection is critical to recovery. Early detection may help prevent other serious complications. Let your doctor know about any symptoms you’re experiencing.