One day, seemingly out of nowhere, you’re hit with intense lower abdominal pain. It’s difficult to stand up straight.

You have a fever and, as you think about the things you’ve eaten or people you’ve spent time with the past few days, the pain refuses to budge. You may also have nausea, constipation, diarrhea, or symptoms reminiscent of a urinary tract infection, such as an increased urge to urinate or burning while doing so. Gastroenterologists see this constellation of symptoms quite often, and a singular diagnosis usually springs to mind: diverticulitis.

What is diverticulitis?

One of the most common gastrointestinal diseases, diverticulitis is an inflammation of tiny sac-like protrusions that form in the wall of the colon. These marble-sized pouches, called diverticula, are found in more than half of Americans over age 60, but most of the time, they don’t cause trouble. The existence of the pouches is called diverticulosis, and it’s generally harmless. Most people don’t even know they have them. But for about 5 percent of people with diverticulosis, those pouches will become inflamed or infected. When that happens, the condition progresses to diverticulitis, which demands immediate medical attention. In fact, the painful condition is responsible for nearly 2 million outpatient visits and 208,000 inpatient admissions a year.

Who develops diverticulitis?

We are just now starting to truly understand why people get diverticulitis. It has long been blamed on a low-fiber diet, but while a high-quality diet is associated with reduced diverticulitis risk, the truth is that genetics, not diet, are responsible for about 50 percent of one’s risk. Siblings of patients with diverticulitis, for instance, are believed to have a threefold higher risk of developing it themselves. Researchers using genetic markers very recently found that genes related to obesity and type 2 diabetes are associated with an increased risk of diverticulitis.

That said, nutrition does have an impact, with a diet high in fruits, vegetables, whole grains, poultry, and fish linked with reduced diverticulitis risk, and vegetarians enjoying some protection over carnivores. A high-fiber diet is important to manage diverticulitis or possibly even avoid it in the first place. When researchers followed 50,000+ health professionals for 24 years, they found that those who consumed the most fiber (an average of 28.5 grams a day) had the lowest risk of developing diverticulitis, and those who consumed the least fiber (12.5 grams a day, on average) had the highest risk. Fiber should come from foods, not supplements.

Vigorous physical activity is also associated with a reduced risk. Diverticulitis is more common among men than women at younger ages, but over age 60, rates are higher for women. Regular use (at least twice a week) of aspirin or nonsteroidal anti-inflammatory drugs such as ibuprofen increases risk, as does obesity, smoking, and the use of hormone replacement therapy for menopause.

Immunocompromised patients— those with cancer or rheumatological conditions, for example—tend to experience diverticulitis at higher rates than the general population, possibly due to chronic steroid use. Interestingly, these patients often present with milder symptoms, delaying diagnosis. They also experience more complications.

Pain is the number one symptom

The pain usually appears suddenly, most often in the left lower quadrant of the abdomen. Patients often describe it as the worst pain they’ve ever had. Even a mild episode can make it difficult to walk. Other symptoms can include fever, constipation (excess inflammation may prevent stool from moving through the colon), diarrhea, and urinary symptoms because an inflamed colon is sitting atop the bladder.

Most people see their primary care physician or visit an emergency room when the pain begins. Your doctor will draw blood to see if you have an elevated white blood cell count, which indicates possible infection. He or she may also run blood tests to confirm inflammation and will rule out a urinary tract infection. An abdominal CT scan is also strongly recommended with the first episode to identify and diagnose diverticulitis and also help determine severity.

Three types of diverticulitis

Most people have acute uncomplicated diverticulitis. Somewhere between 94 and 97 percent of these patients can be successfully treated on an outpatient basis with rest and a clear liquid diet for a few days. The pain usually improves within about two weeks.

A small (less than 10 percent) proportion of uncomplicated diverticulitis patients continue to experience symptoms for weeks to months. This is called smoldering diverticulitis and indicates ongoing inflammation, like a fire that is almost extinguished, but not quite. This type of diverticulitis may require antibiotics or surgery to remove the inflamed part of the colon. Fortunately, about 75 percent of patients will never have another episode. The rest will experience recurrences once a year or even multiple times a year.

About 5 percent of people with acute uncomplicated diverticulitis will go on to develop complicated diverticulitis, involving an abscess or hole in the wall of the colon, through which gas and fluid escape. These patients are almost always hospitalized, require antibiotics, and may need to have a temporary drain inserted in their abdomen to promote healing. Surgery to remove part of the colon may be necessary in some cases.

What happens after a flare-up?

Your gastroenterologist will tell you when to progress from a clear liquid diet (during an episode) to low-fiber solid foods (eggs, cooked fruit, pasta, dairy foods) and then, once all symptoms have subsided, to a high-fiber routine (produce, beans, brown rice, bran and whole-grain cereals). It’s important to maintain communication with your doctor during the clear liquid diet phase to ensure you don’t lose too much weight.

Some people with diverticulitis will experience chronic gastrointestinal (GI) pain and, eventually, be diagnosed with irritable bowel syndrome (IBS). In a Swedish trial, periodic abdominal pain was reported by nearly half of uncomplicated diverticulitis patients at one-year follow-up. This IBS pain is sometimes treated with a low dose of a tricyclic antidepressant such as amitriptyline (Elavil), imipramine (Tofranil), or nortriptyline (Pamelor). These drugs help reduce stomach sensitivity by blocking pain signals sent from the GI tract to the brain.

Six to eight weeks after diverticulitis symptoms resolve, you should have a colonoscopy to rule out malignancy, as colon cancer can resemble diverticulitis on a CT scan. The risk is higher in patients with complicated diverticulitis.

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