What to know about diverticulitis, after Sen. John McCain's surgery

On Monday, the office of Senator John McCain released a statement saying he was admitted to the Mayo Clinic in Phoenix, Arizona and underwent surgery for diverticulitis.

The condition is very common in the United States and has many variations and treatment options, depending on the individual situation. The statement from McCain's medical team does not elaborate on the circumstances that led his physicians to recommend surgery, how it was performed or whether it was an emergency situation.

The treatment may be simple and uncomplicated, requiring 10 to 14 days of oral antibiotics, or it may require an extremely complex surgery with extensive rehabilitation.

Below are some answers to some common questions about diverticulitis:

What is diverticulitis?

The colon is meant to be smooth-walled. Diverticulitis is an inflammatory condition attacking a sac-like pouch protruding from the colon wall, called a diverticuli. Some believe fecal matter and bacteria can become stuck in these outpouchings, triggering an inflammatory response from the body to fight it. Others believe the inflammation and distress is caused by slow erosion of the colon wall because of the increased pressure in the diverticuli.

What causes it?

There is not a single “cause” of diverticular disease, but diet plays a large role. The low fiber, high fat, red meat diets more commonly found in the West are often the culprit. Among Western populations, approximately 50 percent of people over the age of 60 and 70 percent over the age of 80 develop diverticular disease.

In less developed countries, diverticular disease is rare -- the theory is that their diets have more fiber, which works as a preventative mechanism. Studies have shown when immigrants settle in the West and adopt Western diets, they develop diverticular disease at the same rate as others in the West. There is a rising incidence of diverticulitis in countries where there is increasing popularity of Western food.

Smoking, obesity, physical inactivity and certain medications are also risk factors for developing diverticular disease. Fortunately, only 20 percent of patients with diverticular disease will develop symptoms that needs medical treatment.

The symptoms of diverticulitis

The classic patient who has diverticulitis has acute, sudden abdominal pain, most commonly in the left lower quadrant of their belly, with nausea and/or vomiting. Fever may or may not be present. Patients may or may not have changes in bowel movements, either constipation or diarrhea.

One of the challenges with diverticulitis is that it often does not appear to be what it is. A known variant called cecal diverticulitis, which is more common in younger patients and in the developing countries, has all the symptoms of appendicitis. The pain starts and is most severe on the right, lower quadrant of the abdomen with associated nausea and/or vomiting. The inflammation may irritate the membrane that surrounds the entire gut, which results in pain that spreads all over the abdomen. If the patient develops a perforation or an abscess on the gut wall, the patient may have chills, rigors, weakness, headaches, dizziness, etc.

Diagnosing diverticulitis

For people who are younger, relatively healthy, a doctor often make the diagnosis by taking a history and performing a physical exam. They may start with antibiotics to fight the bacterial infection and see if there is improvement. Alternatively, the diagnosis can be made with imaging, most commonly a CT scan. Blood tests can suggest diverticulitis, but are not definitive in making the diagnosis.

How serious is diverticulitis?

Diverticulitis can have severe complications, most notably peritonitis, or inflammation of the organ membranes, that can progress to severe sepsis, or bacterial contamination in the rest of the body. Fortunately, this is rare.

Most patients have symptoms severe enough that they head to a doctor and the diagnosis is common enough that it is usually made on a first or subsequent visit. Diverticulitis has a wide spectrum and there are staging classification systems that health care providers may use to determine the level of severity.

Hospitalization is not always necessary. A first-time, uncomplicated case of diverticulitis usually does not require an admission to the hospital and can be treated with outpatient antibiotics, along with close follow-up with a doctor. This depends on age, other medical conditions, access to follow up, if there are complications present and an evaluation of the treating physician of whether the patient will improve as an outpatient.

Not all cases of diverticulitis need surgery, either. Depending on age, risk factors, severity of symptoms, presence of complications, and overall clinical evaluation by a health care provider, a patient may be admitted to the hospital for IV antibiotics or possibly surgery. For those who have had multiple courses of diverticulitis or had a particularly complicated course, physicians may discuss possible elective surgery as an outpatient after weighing risk and benefits.

What are the complications of diverticulitis?

The most serious complication is a large perforation of the colon wall. That would mean the inflammatory response is so severe or persistent that the colon splits, forms a hole and spills bacteria and fecal matter into the abdomen. Patients with a large perforation are usually severely ill, require an emergency surgery and often need intensive care. A large perforation is very rare.

To a much smaller degree, there can be microperforations, which may wall off into an abscess. Depending on size and severity, doctors may recommend surgery or a radiology procedure to drain the abscess and heal the colon wall. They may elect to treat with IV antibiotics if the hole is very small.

For patients who have multiple bouts of diverticulitis, chronic diverticulitis, or diverticulitis that went untreated for a long time, they may develop strictures in the colon –- a physical obstruction can cause uncontrolled vomiting and an inability to pass gas. These patients usually need a surgical procedure and a possible bowel resection.

Can diverticulitis come back?

Unfortunately, yes. It varies based on person to person, but the likelihood is high. Repeat episodes of diverticulitis are more likely to be admitted to the hospital and more likely to need surgery; however, every patient is different, and every case needs to be evaluated by a health care provider with benefits and risks weighed to determine appropriate course of treatment.

David J. Kim, MD is a final year Emergency Medicine resident at the University of California, Los Angeles, working with the ABC News Medical Unit in New York.