Appendicitis, or epityphlitis, is a condition characterised by inflammation of the appendix. While mild cases may resolve without treatment, most require removal of the inflamed appendix, either by laparotomy or laparoscopy. Untreated, mortality is high, mainly due to peritonitis and shock.

Causes

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The causes of appendicitis are generally unknown, but the leading theory is that obstruction of the appendiceal orifice is the inciting factor. Obstruction may come from fecal matter lodged in the appendix, impaction of mucous, a small tumor (such as a carcinoid), or even a small blood clot. Viral infections, which can cause ulceration of the lining, can also lead to obstruction of the appendix through proliferation of lymphatic tissue in its walls. A viral etiology is a possible explanation for seasonal variations in rates of appendicitis and clustering of cases. Regardless of the cause, obstruction of the appendix may lead to progressive appendiceal distension. This distension increases the pressure within the appendix, which in turn impairs its blood supply. Deprived of blood, the appendix loses the ability to fight infection and fecal bacteria begin to grow out of control. Although spontaneous recovery can rarely occur, with time and lack of treatment the walls of the appendix eventually become gangrenous from the infection and lack of blood flow. As bacteria begin to leak out through the dying walls, pus forms within and around the appendix (suppuration). The end result of this cascade is appendiceal rupture causing peritonitis, which may lead to septicemia and eventually death.

Although the model described above is traditionally taught in medical schools, histories of patients operated for appendicitis do not often correlate well with such a single disease progression. Specifically, those with atypical histories have findings at surgery that are consistent with a suppurative process that starts at the onset of symptoms and then smolders. Patients with typical histories may have findings suggesting resolution. Histories to suggest rupture of the appendix while patients are being diagnostically observed are exceedingly rare.

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