Diseases of the Appendix: Inflammation, Mucocele, and Tumors

Inflammatory changes of the vermiform appendix are the most frequent cause of laparotomy in western countries, where the incidence of appendicitis is approximately 10 times that in eastern countries.

The appendix is part of the cecum, and its abdominal marking usually lies in the transition of the outer to the middle third of an imaginary line drawn from the anterosuperior iliac spine to the umbilicus (the McBurney point). However, because of embryologic development and the mobility of the cecum, the appendix may lie anywhere in the abdominal cavity ( Fig. 89.1 ). Furthermore, it is a rudimentary organ, narrow and thin, and may be positioned retrocecally or may fall into the pelvis. The layers of the appendix are the same as those in other parts of the intestinal tract, but it is not enwrapped by visceral peritoneum, and the longitudinal muscle envelops the entire circumference.

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Variations in Position and Diseases of the Appendix.

It is proposed that obstruction of the lumen of the appendix followed by infection is the cause of acute appendicitis. In the initial stage, acute appendicitis is confined to the mucous membranes, which become edematous and hyperemic, and are invaded by white blood cells (WBCs). If the inflammatory process subsides, which rarely occurs, but involves other coats of the appendix in an acute suppurative process, the whole organ becomes enlarged, and a fibrinous or fibropurulent exudate covers the appendix. Abscesses may form in the appendiceal wall and lead to gangrenous appendicitis. Necrosis and putrefaction of the entire appendiceal tissues may lead to perforation. Once infected material spills into the abdominal cavity, peritonitis may form a periappendiceal abscess or diffuse peritonitis. Depending on the position of the appendix, it may spill into the pelvis or any location in the abdominal cavity.

Rarely, the suppurative process may heal without medical attention. The resultant fibrosis of the wall can lead to the formation of a future cyst or mucocele when mucus is secreted into the fibrosed area. This type of cystic tumor may be benign but must be differentiated from adenocarcinoma. Malignant tumors can spill into the entire abdominal cavity, causing pseudomyxoma peritonei.