INCIDENCE AND EPIDEMIOLOGY
Appendicitis occurs more frequently in Westernized societies. Although its incidence is decreasing for uncertain reasons, acute appendicitis remains the most common emergency general surgical disease affecting the abdomen, with a rate of approximately 100 per 100,000 person-years in Europe and the Americas or about 11 cases per 10,000 people annually. Approximately 9% of men and 7% of women will experience an episode during their lifetime. Appendicitis occurs most commonly in 10- to 19-year-olds, although the average age at diagnosis appears to be gradually increasing, as is the frequency of the disease in African Americans, Asians, and Native Americans. Overall, 70% of patients are less than 30 years old and most are men; the male-to-female ratio is 1.4:1.
One of the more common complications and most important causes of excess morbidity and mortality is perforation, whether it is contained and localized or unconstrained within the peritoneal cavity. In contrast to the trend observed for appendicitis and appendectomy, the incidence of perforated appendicitis (~20 cases per 100,000 person-years) is increasing. The explanation for this phenomenon is unknown. Approximately 20% of all patients have evidence of perforation at presentation, but the percentage risk is much higher in patients under 5 or over 65 years of age.
PATHOGENESIS OF APPENDICITIS AND APPENDICEAL PERFORATION
Appendicitis was first described in 1886 by Reginald Fitz. Its etiology is still not completely understood. Fecaliths, incompletely digested food residue, lymphoid hyperplasia, intraluminal scarring, tumors, bacteria, viruses, and inflammatory bowel disease have all been associated with inflammation of the appendix and appendicitis.
Although not proven, obstruction of the appendiceal lumen is believed to be an important step in the development of appendicitis. In some cases, obstruction leads to bacterial overgrowth and luminal distension, with an increase in intraluminal pressure that can inhibit the flow of lymph and blood in some cases. Then, vascular thrombosis and ischemic necrosis with perforation of the distal appendix may occur. Any perforation that occurs near the base of the appendix should raise concerns about another disease process. Most patients who will perforate do so before they are evaluated by surgeons.
Appendiceal fecaliths (or appendicoliths) are found in approximately 50% of patients with gangrenous appendicitis who perforate but are rarely identified in those who have simple disease. As mentioned earlier, the incidence of perforated, but not simple, appendicitis is increasing. The rate of perforated and nonperforated appendicitis is correlated in men but not in women. Together these observations suggest that the underlying pathophysiologic processes are different and that simple appendicitis does not always progress to perforation. Furthermore, some cases of simple acute appendicitis may resolve spontaneously or with antibiotic therapy, and recurrent disease is remotely possible. The relative frequency of these events is unknown.
When perforation occurs, the resultant leak may be contained by the omentum or other ...