Acute appendicitis may occur in all age groups but is most common in older children and young adults. It is rare in infants, probably because of the conical nature of the appendix, which permits easier entry and exit of stool. In children up to 4 to 6 years of age and in the elderly, diagnosis is difficult and often not made until perforation has occurred. The incidence is equal in males and females but increases in males during early adulthood, after which the sex ratio again becomes equal.

PATHOGENESIS

Acute appendicitis is initiated by obstruction of the lumen by stool (fecalith), fibrous band, lymphoid hyperplasia, or a foreign body. The normal mucosal secretion of the appendix collects distal to the site of the obstruction, which leads to an increase in intraluminal pressure. This causes first interference with venous outflow and subsequently, as pressure increases, with arterial blood inflow. Ulceration of the mucosa occurs with infiltration of the wall of the appendix by bacteria. The resultant infection may lead to gangrene, necrosis, and perforation.

DIAGNOSIS

Symptoms and Signs

In a classical case of acute appendicitis, the patient gives a history of periumbilical pain associated with nausea and vomiting that migrates and localizes in the right lower quadrant. This may occur within 1 to 2 or 12 to 18 hours. Vomiting usually consists of only 1 or 2 episodes and begins after the onset of pain. If vomiting precedes the pain, the patient probably does not have appendicitis.