Description

• Acute inflammation of the appendix
• Simple or uncomplicated appendicitis occurs when there is no clinical or radiologic sign of perforation. Complicated or perforated appendicitis is defined by a palpable mass and phlegmon, perforation, or abscess on imaging.
• Arising from the base of the cecum in right lower quadrant (RLQ), the appendix can be anterior, posterior, medial, or lateral to the cecum as well as in the pelvis; vascular supply provided by appendicular artery, a branch of the ileocolic artery; nerve supply derived from the superior mesenteric plexus
• Most common cause of acute surgical abdomen

Epidemiology

• Predominant age: 10 to 30 years; rare in infancy; although uncommon, it can be more challenging to diagnose in elderly.
• Predominant sex: slight male predominance
  • Ages 10 to 30 years: male > female (3:2)
  • Age >30 years: male = female

Incidence

• 1 case per 1,000 people per year
• Lifetime incidence of 1 in every 15 people (7%)

Pregnancy Considerations

• Most common extrauterine surgical emergency
• Incidence similar in pregnancy
• Higher rate of perforation; more likely to present with peritonitis

Etiology and Pathophysiology

Obstruction of the appendiceal lumen is thought to lead to distention, ischemia, and bacterial overgrowth. Without intervention, appendicitis can lead to perforation and subsequent abscess formation or generalized peritonitis. Causes of obstruction are as follows:

• Fecaliths (most common)
• Lymphoid tissue hyperplasia (in children)
• Vegetables, fruit seeds, and other foreign bodies
• Intestinal worms (ascarids)
• Strictures, fibrosis, neoplasms

Genetics
First-degree relative with history of appendicitis increases risk; no direct genetic link found.

Risk Factors

Adolescent males, familial tendency, intra-abdominal tumors