Acute Appendicitis

Introduction
Background
Appendicitis is a common and urgent surgical illness with protean manifestations, generous overlap with other clinical syndromes, and significant morbidity, which increases with diagnostic delay. No single sign, symptom, or diagnostic test accurately confirms the diagnosis of appendiceal inflammation in all cases.
The surgeon's goals are to evaluate a relatively small population of patients referred for suspected appendicitis and to minimize the negative appendectomy rate without increasing the incidence of perforation. The emergency department clinician must evaluate the larger group of patients who present to the ED with abdominal pain of all etiologies with the goal of approaching 100% sensitivity for the diagnosis in a time-, cost-, and consultation-efficient manner.
Pathophysiology
Obstruction of the appendiceal lumen is the primary cause of appendicitis. An anatomic blind pouch, obstruction of the appendiceal lumen leads to distension of the appendix due to accumulated intraluminal fluid. Ineffective lymphatic and venous drainage allows bacterial invasion of the appendiceal wall and, in advanced cases, perforation and spillage of pus into the peritoneal cavity.
Frequency

United States

Appendicitis occurs in 7% of the US population, with an incidence of 1.1 cases per 1000 people per year. Some familial predisposition exists.

International

Incidence of appendicitis is lower in cultures with a higher intake of dietary fiber. Dietary fiber is thought to decrease the viscosity of feces, decrease bowel transit time, and discourage formation of fecaliths, which predispose individuals to obstructions of the appendiceal lumen.
Mortality/Morbidity
• The overall mortality rate of 0.2-0.8% is attributable to complications of the disease rather than to surgical intervention.
• Mortality rate rises above 20% in patients older than 70 years, primarily because of diagnostic and therapeutic delay.
• Perforation rate is higher among patients younger than 18 years and patients older than 50 years, possibly because of delays in diagnosis. Appendiceal perforation is associated with a sharp increase in morbidity and mortality rates.
Sex
The incidence of appendicitis is approximately 1.4 times greater in men than in women. The incidence of primary appendectomy is approximately equal in both sexes.
Age
• Incidence of appendicitis gradually rises from birth, peaks in the late teen years, and gradually declines in the geriatric years. The median age at appendectomy is 22 years.
• Although rare, neonatal and even prenatal appendicitis have been reported.
• The emergency department clinician must maintain a high index of suspicion in all age groups.