Symptoms, 5 Types, Causes, Diet, and Treatment



A woman suffers from colitis abdominal pain.

A woman suffers from colitis abdominal pain. There are numerous causes of colitis including infection, inflammatory bowel disease (Crohn’s disease and ulcerative colitis are two types of IBD), ischemic colitis, allergic reactions, and microscopic colitis.Source: Getty Images

An illustration of the colon anatomy.

An illustration of the colon anatomy. Colitis describes inflammation of the inner lining of the colon.Source: MedicineNet

Colitis and the anatomy of the colon

The colon, or large intestine, is a hollow, muscular tube that processes waste products of digestion from the small intestine, removes water, and ultimately eliminates the remnants as feces (stool) through the anus. The colon is located within the peritoneum, the sac that contains the intestine, located in the abdominal cavity.

The colon is surrounded by many layers of tissue. The innermost layer of the colon is the mucosa that comes into contact with the waste products of digestion. The mucosa absorbs water and electrolytes back into the blood vessels that are located just below the surface in the submucosa. This is surrounded by a circular layer of muscles and then another outer layer of longitudinal muscles that run along the length of the colon. The muscles work together to rhythmically squeeze liquid waste from the cecum through the entire length of the colon. Water is gradually removed, turning the waste into the formed stool so that it is excreted out of the anus in solid form.

The colon frames the organs within the peritoneum, and its segments are named based on their location.

  • The colon usually begins in the right lower quadrant of the abdomen, where the terminal ileum, the last part of the small intestine, attaches to the cecum, the first segment of the colon. The appendix is attached to the cecum.
  • The ascending colon begins at the cecum and arises from the right lower abdomen to the right upper abdomen near the liver.
  • The colon then makes a sharp left turn called the hepatic flexure (hepatic=liver), and is referred to as the transverse colon, as it makes its way to the left upper quadrant of the abdomen near the spleen.
  • There is a sharp downward turn called the splenic flexure, and it is referred to as the descending colon as it runs from the left upper quadrant to the left lower quadrant of the abdomen.
  • When it descends into the pelvis, it is referred to as the sigmoid colon.
  • The last several centimeters of the colon is referred to as the rectum.
  • The anus is the final portion of the colon.

An illustration of the flagellated bacterium.

An illustration of the flagellated bacterium. These infections usually occur because the patient has eaten contaminated food.Source: Getty Images

Infectious causes of colitis

Many bacteria reside in the colon; they live in harmony with the body and cause no symptoms. However, some infections can result if a virus, bacteria, or parasite invade the small and/or large intestine.

Common bacteria that cause colitis include

These infections usually occur because the patient has eaten contaminated food. Symptoms can include diarrhea with or without blood, abdominal cramps, and dehydration from water loss because of numerous watery, bowel movements. Other organs can also be affected by the infection or the toxins that the bacteria can produce.

Clostridium difficile, commonly referred to as C. diff, is a bacterial cause of colitis that often occurs after a person has been prescribed an antibiotic or has been hospitalized. C. diff is found in the colon of healthy people and coexists with other “normal” bacteria. But when antibiotics are prescribed, susceptible bacteria in the colon can be destroyed, allowing the clostridia to grow unchecked, causing colitis. Patchy membranes form over the colon mucosa and some health care professionals refer to C. diff colitis as pseudomembranous colitis. The bacteria also may be found on many surfaces in the hospital (for example, bedrails, toilets, and stethoscopes), and the infection may spread from person to person (it is highly contagious). Unfortunately, this infection is becoming more common outside the hospital environment, and people can develop community-acquired C. diff colitis without exposure to antibiotics or a medical facility.

Worldwide, the most common parasite infection to cause colitis is Entamoeba histolytica. It is acquired by drinking infected water and can also be passed from person to person because of poor sanitation and hygiene.


Ulcerative Colitis: Symptoms, Diet, Treatment, Causes
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An endoscopic view of ulcerative colitis.

An endoscopic view of ulcerative colitis. Ulcerative colitis and Crohn’s disease are the two types of inflammatory bowel disease (IBD) that cause colitis.Source: Getty Images


What is Crohn’s disease?
See Answer

A mother holds a crying baby drinking a bottle.

There are two types of microscopic colitis. Either collagen or lymphocytes (a type of white blood cell) infiltrate into the layers of the wall of the colon, presumably as a result of inflammationSource: iStock

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A man holds his stomach in pain.

A man holds his stomach in pain from inflammation.Source: Getty Images

A medical receptionist on the phone schedules patient appointments.

Seek medical care if diarrhea persists for more than two to three weeks, if there is blood in the stool, fever, or the person has signs of dehydration.Source: iStock

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A patient medical history form.

Most often colitis is treated by a primary health care provider or internal-medicine specialist, especially when the colitis is first diagnosed and the cause is uncertain.Source: iStock

What kind of doctor diagnoses and treats colitis?

Most often colitis is treated by a primary health care provider or internal-medicine specialist, especially when the colitis is first diagnosed and the cause is uncertain. Once the cause is found, that health care provider may be the only person needed to continue care. Should there be a need for further investigation and diagnostic testing, specialists may be consulted, such as a gastroenterologist. If an infection is the cause of colitis, an infectious-disease specialist may be consulted. In some cases, other specialists may be involved in treatment, such as surgeons and interventional radiologists.

Patient history

  • In patients with abdominal pain and diarrhea, it is important to find out when the symptoms began, how long they have lasted, whether they come and go, and what makes them better or worse.
  • Travel history is important, especially if the patient has recently visited an area with potentially contaminated water supply or poor food hygiene. Patients often ask if the symptoms are caused by food poisoning, but that is a difficult question to answer immediately. Usually this occurs with the consumption of poorly handled or stored food in a home or a family gathering event and symptoms occur within a few hours after the food was eaten. Moreover, others at the gathering may experience similar symptoms.
  • Blood in the stool, whether it is mixed in with the bowel movement or just drops in the toilet bowl, is not normal. While it may be due to hemorrhoids, other potential causes that are more worrisome may need to be explored. Questions might be asked about bowel habits, weight loss, weakness, or family history of bowel disorders, including cancer or colon polyps. Depending on the health care professional’s concerns, information may need to be obtained about other body systems, past medical history, social habits (including smoking, drinking, and occupational hazards or risks).

A doctor takes a woman's blood pressure.

A doctor takes a woman’s blood pressure. Signs of more severe disease with dehydration may include orthostatic changes in blood pressure and pulse rate, where vital signs are taken both laying down and standing up.Source: iStock

What happens during a physical exam for colitis?

Once the history is taken, a physical examination will help determine the potential causes of the symptoms.

  • Signs of more severe disease with dehydration may include orthostatic changes in blood pressure and pulse rate, where vital signs are taken both laying down and standing up. In dehydrated patients, have had rectal bleeding, or are anemic, blood pressure and pulse may be normal when they are taken when the patient lies flat but may change when standing — the blood pressure falls and the pulse rate rises. Prescription medications, especially beta-blockers prescribed for high blood pressure, may falsely lower the pulse rate and not allow it to increase.
  • Temperature is checked for fever.
  • Examination of the abdomen includes palpating or feeling for tenderness and masses in the abdomen. Bowel sounds are often listened to with a stethoscope.
  • The exam also may include a rectal examination to test the stool for blood and feel for a possible rectal mass.
  • If there is a concern for ischemic bowel as the cause of colitis, the examination also may assess the heart and blood vessels, looking for signs of atherosclerosis or narrowing of the arteries. This might include listening to the heart and palpating or feeling pulses in the neck, arms, and legs and listening with a stethoscope to the large blood vessels in the body including the carotid and femoral arteries and the aorta.
  • In patients where the clinical diagnosis of colitis is secondary to a viral infection, no further testing may be needed. However, this would not apply to a patient who appears ill, dehydrated, or has significant pain, fever, or blood in the stool.

A laboratory technician examines a vial of blood.

A laboratory technician examines a vial of blood.Source: Getty Images

A medical illustration of a colonoscopy.

A medical illustration of a colonoscopy. Computerized tomography and barium enema are tests that are sometimes ordered to help diagnose the potential cause of colitis.Source: Getty Images

A doctor talks to a female patient.

A doctor talks to a female patient. What foods help soothe colitis flares? What foods should I avoid if I have colitis?Source: Getty IMages

What is the treatment for colitis?

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.

Medically Reviewed on 2/25/2021


Crohn’s and Colitis Foundation of America. “Inflammatory Bowel Disease and Irritable Bowel Syndrome: Similarities and Differences.” July 2014.

Crohn’s and Colitis Foundation of America. “Living with Crohn’s & Colitis.”

Crohn’s & Colitis UK. “Research reveals unexpected features of the immune system in Crohn’s and Colitis.” March 14, 2019. <>.

Kasper, D.L., et al., eds. Harrison’s Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.


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