- 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
- Predominant age: 10 to 30 years; rare in infancy; while uncommon, 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
- 1 case per 1,000 people per year
- Lifetime incidence 1 in every 15 people (7%)
- 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
First-degree relative with history of appendicitis increases risk; no direct genetic link found.
Adolescent males, familial tendency, intra-abdominal tumors
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