Diverticulitis occurs when diverticula or small, abnormal sacs in the large intestine, become infected and inflamed. According to the American College of Gastroenterology (ACG), about 10 to 25 percent of patients with diverticulosis (a condition characterized by the presence of diverticula) will eventually develop diverticulitis.

The symptoms of diverticulitis depend on the degree of inflammation and the presence of any complications. The most common signs and symptoms of the condition are tenderness, pain and an increased level of white blood cells. Other symptoms include constipation or diarrhea, nausea and vomiting. Peritonitis is the most serious complication of diverticulitis. It occurs when an abscess or sac ruptures or infection leaks out of the abscess and spills into the abdominal cavity.

Diverticulitis is usually diagnosed based on medical history, physical examination and blood tests. Most patients display classic signs and symptoms. Therefore, diagnostic imaging tests are often unnecessary. However, certain imaging tests (e.g., CAT scan, ultrasound) may be used in some cases.

The focus of treatment is clearing the infection and inflammation, resting the colon and preventing or minimizing complications. Bed rest, liquid or low-fiber diets and antibiotics are the typical treatment regimen. In most cases, the symptoms go away after three to four days of antibiotic therapy, though antibiotics will be required for a longer period. Few diverticulitis patients require surgery. When surgery is required, the diseased region of the colon is removed and the healthy sections are joined together to allow normal bowel function. Patients with large diverticular abscesses may require a temporary colostomy and reanostomosis as a later operation.