Diverticulitis occurs in people with diverticulosis. Diverticulitis is swelling of an abnormal pouch (diverticulum) in the intestinal wall. 

Persons most commonly affected: Both sexes and uncommon before the age of 40. 
Organ or part of body involved: Large Intestine
Symptoms and indications: Diverticulitis symptoms can feel like appendicitis, except you'll generally have pain in the lower left side of your abdomen, instead of the lower right side. The pain is usually severe and comes on suddenly, but sometimes you may have mild pain that becomes worse over several days and fluctuates in intensity. You may also have abdominal tenderness, fever, nausea, and constipation or diarrhea. Less common signs and symptoms of diverticulitis may include: Vomiting, Bloating, Bleeding from your rectum, Frequent urination, Difficulty or pain while urinating, and Tenderness in your abdomen when wearing a belt or bending over. 
Causes and risk factors: A low-fiber diet causes diverticular disease. Constipation
Prevention: Eat more fiber -- High-fiber foods, such as fresh fruits and vegetables and whole grains, soften waste material and help it pass more quickly through your colon. This reduces pressure inside your digestive tract. Aim for 25 to 30 grams of fiber each day. An apple or 1/2 cup of spinach contains 2 to 3 grams of fiber, and 1/2 cup of baked beans contains about 6 grams. Try to substitute fruits, vegetables and grain products for foods high in fat. Be sure to add fiber gradually to avoid bloating, abdominal discomfort and gas. If it's difficult for you to consume 25 to 30 grams of fiber every day, consider using a fiber supplement, such as psyllium. Although commonly recommended, there's little evidence that avoiding eating seeds or nuts prevents recurrent attacks of diverticulitis. 

Drink plenty of fluids -- Fiber works by absorbing water and increasing the soft, bulky waste in your colon. But if you don't drink enough liquid to replace what's absorbed, fiber can be constipating. 

Respond to bowel urges --When you need to use the bathroom, don't delay. Delaying bowel movements leads to harder stools that require more force to pass and increased pressure within your colon. 

Exercise regularly -- Exercise promotes normal bowel function and reduces pressure inside your colon. Try to exercise at least 30 minutes on most days.