Acute sigmoid diverticulitis results from inflammation of a diverticulum that can progress to perforation and abscess formation. Acute sigmoid diverticulitis is usually manifested by fever, leukocytosis, left lower quadrant pain, and, at times, a left lower quadrant mass. Treatment of uncomplicated acute diverticulitis is bowel rest and broad-spectrum antibiotics. After recovery from an initial episode of diverticulitis, the colon should be evaluated by either sigmoidoscopy and barium enema or colonoscopy. Patients who do not respond to medical therapy should undergo computed tomography scan or surgery depending on the clinical situation. Selected abscesses detected on computed tomography scan may be drained percutaneously. Elective resection should be considered after attacks of diverticulitis, depending on age, medical fitness of the patient, and severity of the attack. Complicated diverticulitis is diverticulitis associated with obstruction, stricture, fistula, or abscess. Patients with complicated diverticulitis should undergo resection after one attack. Primary sigmoid resection with anastomosis is performed in patients who meet criteria for a safe anastomosis, including adequate mechanical bowel preparation, healthy bowel. good blood supply, and no tension on the anastomosis. A two-stage procedure, generally Hartmann's resection, is performed for patients with fecal or purulent peritonitis.