With advancing age and the affluent, low-fiber Western diet, the incidence of diverticular disease is increasing. Fortunately, most cases can be managed conservatively without resorting to surgical intervention. Life-threatening complications such as perforation, especially when it is associated with gross fecal contamination, requires urgent aggressive surgical intervention. A 75-year-old man with absolute constipation and pain in the left iliac fossa underwent urgent laparotomy following fluid and antibiotic resuscitation. A posterior perforated sigmoid diverticulitis associated with myofascial necrosis and generalized pelvic emphysema was identified. In cases where perforation occurs posteriorly and the only external manifestation is surgical emphysema, the outcome is generally favorable.