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Pseudomembranous colitis is an inflammatory condition of the colon (large intestine) that occurs in some people who have used antibiotics. It develops when antibiotics disrupt the normal balance between "good" and "bad" bacteria in your colon, causing the proliferation and spread of harmful microorganisms.

Most often, the inflammation in pseudomembranous colitis is associated with an overgrowth of the bacterium Clostridium difficile (C. difficile), although in less than 10 percent of cases, other organisms can be involved.

Pseudomembranous colitis occurs more often in adults than in children, and it's rare in infants because of protective antibodies they received from their mothers. The condition can cause serious symptoms and can even become life-threatening. However, treatment for most cases of pseudomembranous colitis is successful.

Pseudomembranous colitis is sometimes called antibiotic-associated colitis or C. difficile colitis.

The most common and the initial sign of pseudomembranous colitis is watery, and sometimes bloody, diarrhea. Other signs and symptoms include:

• Abdominal cramps and pain
• Fever (which may be higher than 101 F)
• Urge to have a bowel movement (fecal urgency)
• Pus or mucus in your stool
• Nausea
• Dehydration

Symptoms of pseudomembranous colitis can begin within one to two days after you begin using an antibiotic, or they may not occur until several weeks after you discontinue using the antibiotic.

Antibiotics can lead to pseudomembranous colitis by disturbing the normal bacterial balance within your colon, which facilitates the colonization and growth of C. difficile or other bacteria. Potent toxins are released when these bacteria become numerous, causing inflammation of your colon.

The most commonly used antibiotics associated with pseudomembranous colitis are ampicillin, amoxicillin, clindamycin and cephalosporins. However, virtually any antibiotic can cause pseudomembranous colitis. The condition is more likely to occur when you take antibiotics orally rather than through a vein (intravenously). Pseudomembranous colitis also has been associated with antibiotics that you may receive before an operation to prevent surgery-related infections.

Although antibiotics are by far the drugs most often associated with the development of pseudomembranous colitis, other so-called antimicrobial medications (such as antiviral or antifungal drugs) may be responsible. In addition, in people with cancer, chemotherapy may sometimes disrupt the bacteria within the intestines and trigger the development of pseudomembranous colitis.

Antibiotic use is the key risk factor for pseudomembranous colitis. However, other risk factors include:

• Age (older than 60 years)
• Weakened immune system
• Diseases of the colon (such as inflammatory bowel disease and colorectal cancer)
• Intestinal surgery
• Cancer chemotherapy with medications, such as 5-fluorouracil and cisplatin

Pseudomembranous colitis is more common in certain people in hospitals and nursing homes, often when they're receiving drugs or undergoing surgery in which antibiotics are part of the treatment regimen.

Contact your doctor if you develop any of the signs or symptoms associated with pseudomembranous colitis, including constant diarrhea, abdominal pain, and blood or pus in your stool. Particularly if you're taking or have recently taken antibiotics, be sure to contact your doctor if these problems occur.

Your doctor will start by taking a complete medical history, asking about recent or current antibiotic use, and recent hospitalizations and intestinal surgery. He or she will also ask you about signs and symptoms, such as diarrhea and abdominal pain.

A number of medical conditions — Crohn's disease, ulcerative colitis, bacterial infections and parasitic infections — can cause diarrhea and other signs and symptoms similar to those of pseudomembranous colitis. Because of this, you'll need tests to definitively diagnose pseudomembranous colitis and rule out other disorders.

Your doctor will likely order one or both of the following tests to help make a diagnosis of pseudomembranous colitis:

• Stool sample. A laboratory evaluation conducted on one or more stool samples can detect the toxin released by C. difficile. False-negative results are possible with this test. Doctors sometimes repeat the test if it doesn't show the presence of C. difficile but there are strong reasons to suspect the disorder.
• Colon examination. In a colonoscopy or sigmoidoscopy, your doctor uses a tube with a miniature camera at its tip. The tube is advanced through your rectum and into your colon, allowing your doctor to examine the interior of your colon for signs of pseudomembranous colitis. If you have pseudomembranous colitis, the exam may show raised, yellow plaques or lesions within your colon, as well as swelling.

Your doctor may also request a computerized tomography (CT) scan to get detailed images of your colon. The CT scan can show a thickening of the wall of your colon, which may suggest pseudomembranous colitis.

He or she may also order blood tests, because an abnormally high white blood cell count (leukocytosis) may indicate pseudomembranous colitis.

By the time your doctor detects pseudomembranous colitis, you may already be seriously ill. If the condition isn't successfully treated at the time of diagnosis, a number of complications can develop, including:

• Abnormally low levels of potassium in your blood (hypokalemia), due to the loss of potassium during excessive diarrhea
• Dehydration leading to abnormally low blood pressure (hypotension), related to significant loss of fluids due to diarrhea
• Kidney failure, due to severe dehydration resulting from diarrhea
• Abnormally low levels of protein in your blood (proteinemia) from a leaky colon wall
• A hole in your bowel (perforated colon), which can lead to an infection of your abdominal cavity
• Toxic megacolon, a rare but serious distension of the colon, leaving it incapable of expelling gas and stool, which could your colon to rupture

Most people respond well to treatment, but pseudomembranous colitis can be fatal without effective treatment. The risk of death is highest in older adults.

Once the diagnosis of pseudomembranous colitis is made, your doctor will stop the antibiotic that was associated with development of the disorder. Sometimes, this may be enough to resolve your condition, or at least ease signs such as diarrhea. Once you begin treatment for pseudomembranous colitis, signs and symptoms may begin to improve within a few days, and they often resolve completely within two weeks.

To treat more severe cases of pseudomembranous colitis, your doctor will choose from among a number of medications, particularly antibiotics other than the one associated with your illness.

Most common medications
The Centers for Disease Control and Prevention (CDC) recommends the antibiotic metronidazole (Flagyl) as the first drug of choice for treating disorders associated with C. difficile bacteria. But if you're quite ill, your doctor may prescribe the antibiotic vancomycin (Vancocin) first, because it can produce a more rapid response.

If you're a pregnant women in your first trimester, don't take metronidazole because of the risk of birth defects. It's also a poor choice if you're breast-feeding because the drug's effect on babies is unknown. Doctors also generally avoid prescribing this medication in children younger than 10 years old. In certain cases, doctors may give a combination of vancomycin and metronidazole.

Rifaximin (Xifaxan) is another antibiotic that doctors sometimes use to manage pseudomembranous colitis.

The antibiotics used to treat pseudomembranous colitis are usually given by mouth. However, depending on the severity of the inflammation, you may be treated with these medications intravenously, via an enema, or through a tube inserted through your nose and threaded into your stomach (nasogastric tube).

Recurrent inflammation
Even in people who are treated successfully, pseudomembranous colitis may recur in about 15 percent to 20 percent of cases within weeks to months after treatment has stopped. You may need a second or third round of drug therapy to resolve your condition.

If your infection comes back, your doctor may treat you again with metronidazole. If it comes back still again, you may receive a prolonged course of vancomycin to get rid of the infection.

Your doctor may also give you a yeast called Saccharomyces boulardii or another probiotic to help restore your colon's normal bacteria and prevent a relapse. Probiotics are dietary supplements or foods that contain beneficial bacteria normally found in your intestinal tract. Small studies have shown some benefits with probiotics, but you may need to take them long term if you have had many relapses.

Why antibiotics as a treatment?
Antibiotics cause pseudomembranous colitis because they kill the normal bacteria in your colon and allow toxic C. difficile to grow. Although it may seem strange to use antibiotics to treat a disorder caused by antibiotics, treatment with antibiotics eradicates the C. difficile and allows the normal bacteria to grow back, restoring the balance of bacteria in your colon to what it was before any antibiotics were given.

Dealing with dehydration
If you become dehydrated due to diarrhea, your doctor will prescribe electrolyte solutions to replace lost fluids. At times, these rehydration solutions will be administered intravenously.

Don't take anti-diarrheal medications — such as loperamide (Imodium) or the combination drug diphenoxylate and atropine (Lomotil) — without your doctor's knowledge. These drugs could worsen the signs and symptoms of pseudomembranous colitis.

When surgery is an option
If antibiotic treatment doesn't reduce colonic inflammation and ease your symptoms, and your condition worsens, your doctor may recommend intestinal surgery. This is rare, however; surgery is needed in less than 1 percent of people with pseudomembranous colitis.

Surgery becomes an option in people who have severe pain, progressive organ failure and inflammation of the lining of the abdominal wall (peritonitis). Surgery typically involves removal (resection) of the diseased section of the bowel (subtotal colectomy).

Antibiotics are used only when your doctor believes they are necessary; make sure you should take them exactly as prescribed. Particularly if you've already had an episode of pseudomembranous colitis, be sure to discuss this disease history with your doctor before taking antibiotics again.

Some research suggests that the use of probiotics can prevent pseudomembranous colitis when used before, during and after treatment with antibiotics. The most commonly used probiotic in these circumstances is Saccharomyces boulardii, which is more widely used in Europe than in the United States. However, avoid this supplement if you have yeast allergies.

To support your doctor's treatment for pseudomembranous colitis, several self-help measures may benefit you:

• Drink fluids. Drink water and other clear fluids, such as apple juice, tea and bouillon. Stay away from carbonated beverages, orange juice and other citrus drinks, alcohol, and caffeinated drinks, all of which can make your signs and symptoms worse.
• Eat several meals of small portion sizes throughout the day. This is better than eating two or three larger meals because the smaller meals tend to promote more normal bowel movements.
• Eat foods that can help ease diarrhea. These include rice, bananas, plain baked potatoes and toast.
• Avoid high-fat, fried or spicy foods. These can worsen your symptoms.