Diverticulitis is a painful condition that occurs when pouches known as diverticula form within the wall of the colon and become infected. The cause of diverticulitis is unknown, but one theory suggests that diets that are low in fiber may lead to constipation, causing the muscles to strain when stool is passed. Chronic straining may cause diverticulitis and the formation of diverticula in the colon. Diverticulitis may also occur if stool and bacteria are caught in pouches within the colon. Common symptoms include fever, nausea, pain in the lower abdomen, vomiting and changes in bowel habits. Most cases of diverticulitis can be treated with antibiotics and a liquid diet. In more severe cases, surgery may be required to repair any damage.