Diverticulitis is a common digestive disease which involves the formation of pouches (diverticula) within the bowel wall. This process is known as diverticulosis, and typically occurs within the large intestine, or colon, although it can occasionally occur in the small intestine as well. Diverticulitis results when one of these diverticula becomes inflamed. Patients often present with the classic triad of left lower quadrant pain, fever, and leukocytosis (an elevation of the white cell count in blood tests). Patients may also complain of nausea or diarrhea; others may be constipated. Less commonly, an individual with diverticulitis may present with right-sided abdominal pain. This may be due to the less prevalent right-sided diverticula or a highly redundant sigmoid colon. Some patients report bleeding from the rectum. The most common symptom of diverticulitis is abdominal pain. The most common sign is tenderness around the left side of the lower abdomen. If infection is the cause, then nausea, vomiting, fever, cramping, and constipation may occur as well. The severity of symptoms depends on the extent of the infection and complications. Diverticulitis may worsen throughout the first day, as it starts as small pains and/or diarrhea, and may slowly turn into vomiting and sharp pains.