What is appendicitis?

What is Appendicitis?

Appendicitis is an acute inflammatory condition of the appendix that represents the most common abdominal surgical emergency worldwide, occurring at a rate of approximately 96.5-100 cases per 100,000 adults annually. 1, 2

Pathophysiology

• The condition typically begins with obstruction of the appendiceal lumen, most commonly by fecaliths (conglomeration of feces) or parasites, leading to increased intraluminal pressure and subsequent mucosal ischemia 2, 1
• The inflammatory process progresses through three distinct stages: (1) normal appendix, (2) uncomplicated acute appendicitis, and (3) complicated appendicitis (gangrenous or perforated) 3, 2
• In elderly patients, the appendix develops vascular sclerosis with muscular layers infiltrated with fat, creating structural weakness and tendency toward early perforation 2

Clinical Presentation

Classic symptoms include periumbilical pain that migrates to the right lower quadrant, anorexia, nausea, intermittent vomiting, and low-grade fever. 1, 4

• Right lower quadrant pain, abdominal rigidity, and periumbilical pain radiating to the right lower quadrant are the most reliable signs for diagnosis in adults 5
• The pain migration occurs as the parietal peritoneum becomes inflamed 2
• In children, absent or decreased bowel sounds, positive psoas sign, positive obturator sign, and positive Rovsing sign are most reliable diagnostic findings 5
• Approximately 90% of patients presenting with classic symptoms receive a correct diagnosis 1

However, atypical presentations are common, occurring in approximately 50% of patients, which can result in diagnostic delays and increased complications. 3, 4

Epidemiology and Risk Factors

• Lifetime risk varies geographically: 9% in the USA, 8% in Europe, and 2% in Africa 2
• Peak incidence occurs between ages 10-30 years, with decreasing incidence after adolescence 2
• Among patients over 50 years presenting with acute abdominal pain, approximately 15% will have appendicitis compared to nearly 30% of younger patients 2

Advanced age is the most significant risk factor for complicated disease, with elderly patients (>65 years) having perforation rates of 18-70% compared to 3-29% in younger patients. 2

• Mortality risk increases threefold with each decade of age beyond 65 years, reaching more than 16% in nonagenarians 2
• Delayed presentation significantly increases perforation risk, with median duration from symptom onset to definitive care in complicated cases being approximately 4 days 2
• The presence of an appendicolith is strongly associated with progression to complicated disease 2

Disease Classification

Appendicitis is classified as either uncomplicated (approximately two-thirds of cases) or complicated (one-third of cases). 2, 3

• Uncomplicated appendicitis includes simple inflammation without perforation 2
• Complicated appendicitis includes gangrenous appendicitis, perforated appendicitis, periappendiceal abscess, or diffuse peritonitis 2, 6
• Perforation rates vary from 16-40% overall, with higher frequencies in younger age groups (40-57%) and patients older than 50 years (55-70%) 2

Mortality by Disease Stage

• Acute non-gangrenous appendicitis: <0.1% mortality 2, 6
• Gangrenous appendicitis: 0.6% mortality 2, 6
• Perforated appendicitis: approximately 5% mortality 2, 6
• Elderly patients (>65 years): up to 8% overall mortality 2

Diagnostic Approach

Clinical assessment remains the mainstay of diagnosis, though imaging is valuable for confirmation and risk stratification. 7

• Laboratory findings typically reveal elevated leukocytosis with left shift and elevated C-reactive protein 3, 4
• Scoring systems (Alvarado score, Pediatric Appendicitis Score, Appendicitis Inflammatory Response score) can stratify patients as low, moderate, or high risk 3, 5
• Recommended first-line imaging is point-of-care or formal ultrasonography 5
• CT abdomen and pelvis with IV contrast has sensitivity reaching 95% and specificity higher than 95% 4
• In children, ultrasound should be used to confirm appendicitis but not to definitively exclude it, with CT reserved for cases where diagnosis remains uncertain after ultrasound 3
• MRI without IV contrast has 96% sensitivity and 96% specificity and is particularly useful in pregnant patients 3

CT findings of appendicolith, mass effect, or dilated appendix >13 mm identify patients at higher risk for treatment failure with antibiotics (approximately 40% failure rate). 1

Management Principles

Appendectomy (laparoscopic or open) remains the standard first-line treatment for acute appendicitis. 3, 1

• Uncomplicated appendicitis in low-risk patients may not require postoperative antibiotics 2
• Antibiotic therapy alone successfully treats uncomplicated acute appendicitis in approximately 70% of patients at one year, but carries significant recurrence rates 3, 1
• Broad-spectrum antibiotics include piperacillin-tazobactam monotherapy or combination therapy with cephalosporins or fluoroquinolones plus metronidazole 1
• Complicated appendicitis requires appendectomy with postoperative antibiotic therapy for 3-5 days, though discontinuation should be based on clinical criteria such as fever and leukocytosis 3, 2
• Gangrenous appendicitis cannot be managed with conservative antibiotic therapy alone 6

Proper staging of appendicitis is essential as it dictates the appropriate management strategy, antibiotic regimen, and expected outcomes. 2, 6