Appendicitis

Overview

Pathophysiology

1. Luminal obstruction (most commonly by an appendicolith, less often by lymphoid hyperplasia, carcinoid tumor, or other mass)
2. Bacterial overgrowth and mucosal edema
3. Vasocongestion and ischemia
4. Infarction and necrosis
5. Perforation

Clinical Features

Classic Presentation

• Abdominal pain: begins as vague, crampy, periumbilical pain (visceral) that migrates to the right lower quadrant (RLQ) over 12-24 hours (somatic, as parietal peritoneum becomes involved)
• Nausea, vomiting, anorexia
• Low-grade fever (usually appears later)

Physical Examination Signs

These signs are indicators of localized peritonitis rather than specific to appendicitis, and are poorly sensitive/specific in young children. - Sabiston Textbook of Surgery

Atypical Presentations

• Retrocecal appendix (~30%): pain may be flank/back-predominant
• Pelvic appendix: urinary or pelvic symptoms may dominate
• Pregnancy: appendix displaced in <25% of third-trimester patients; loss of rebound due to wall displacement; physiologic leukocytosis confounds labs
• Elderly: often present late with vague symptoms; higher perforation rate
• Young children: often present already perforated; history unreliable

Differential Diagnosis

Diagnostic Workup

Laboratory Tests

• WBC: Elevated (>10,000/µL) in ~90% of cases, usually <18,000/µL; normal WBC does not exclude the diagnosis (10% of cases)
• CRP: Elevated; combined with leukocytosis gives sensitivity as high as 98% when both are elevated - useful to rule out when both are normal in low-pretest-probability patients
• Procalcitonin: Less established than CRP; may indicate perforation
• Urinalysis: Mild sterile pyuria or hematuria can occur (proximity of inflamed appendix to ureter/bladder)
• In reproductive-age females: urine or serum beta-hCG is mandatory

Clinical Scoring Systems

• Score 1-4: Low risk
• Score 5-9: Possible to probable appendicitis
• Note: A score of 1-4 was only 72% sensitive vs. 93% for clinical judgment - scores supplement but do not replace clinical assessment. - Tintinalli's Emergency Medicine

Imaging

Management

Operative (Standard of Care)

• Lower complication rates vs. open
• Faster return to normal activity
• Exception: open appendectomy is preferred when perforation with gross contamination is present

• Cefotetan 2g IV or cefoxitin 2g IV (followed by 3 postoperative doses for coverage)
• Alternatives: ticarcillin-clavulanic acid
• Covers gram-negatives and anaerobes - Goldman-Cecil Medicine

Nonoperative Management (Antibiotics Alone)

• ~29% of antibiotic-treated patients ultimately underwent appendectomy within 90 days
• Surgical intervention has higher treatment efficacy and shorter hospital stay
• Antibiotics alone are an option for select patients with uncomplicated appendicitis - must be counseled about recurrence rates
• Contraindications to nonoperative approach: appendicolith present, evidence of perforation/abscess, immunocompromise, failure to improve in 24-48h - Fischer's Mastery of Surgery; Sabiston Textbook of Surgery

Perforated Appendicitis

• Mortality rises from 0.0002% (uncomplicated) to 3% with perforation; morbidity from 3% to 47%
• Management depends on presentation:
  • Immediate operation if unstable or early perforation
  • Conservative management (antibiotics + IV fluids ± IR drain) followed by interval appendectomy at 6-8 weeks if well-contained abscess and symptoms >5 days
• Antibiotic duration guided by fever, WBC, source control, and ileus resolution

Pediatric Considerations

• Ultrasound and MRI preferred over CT to avoid radiation risks
• Nonoperative management achievable in 80-90% of uncomplicated cases initially; recurrence rates up to 40% medium-term
• Laparoscopic appendectomy remains preferred by most pediatric surgeons
• COVID-19 coinfection cases are generally managed nonoperatively
• Patients with fecalith are generally not candidates for nonoperative management - Current Surgical Therapy 14e

Complications

• Perforation with peritonitis
• Appendiceal abscess (periappendiceal phlegmon or abscess)
• Pylephlebitis (septic portal vein thrombophlebitis - rare)
• Postoperative wound infection, ileus, bowel obstruction
• Negative appendectomy (rates up to 15% historically; reduced with CT use)

Special Populations

• Pregnancy: Most common surgical emergency in pregnancy; highest risk of maternal/fetal morbidity with perforation. MRI is the preferred imaging (avoids radiation). Appendectomy is safe in all trimesters; laparoscopy is acceptable. - Rosen's EM
• Neutropenic patients: Typhlitis (neutropenic enterocolitis) must be distinguished; management is often more conservative initially. - [Kasprzycki et al., 2024 Systematic Review PMID 39036902]
• Pediatric risk stratification: A 2025 systematic review (Mortazavi et al., Pediatr Surg Int) highlights evolving tools for risk-stratifying pediatric appendicitis.
• Pediatric nonoperative management: A 2026 JAMA Pediatrics meta-analysis (Faria et al.) reevaluated nonoperative management in uncomplicated pediatric appendicitis - important recent update suggesting the approach is viable but requires careful patient selection.

Key Takeaways

1. Classic history: periumbilical pain migrating to RLQ + anorexia + low fever
2. No lab test or score alone rules in/out appendicitis - clinical judgment is paramount
3. CT is the gold-standard imaging in adults; ultrasound/MRI in children and pregnant women
4. Laparoscopic appendectomy is standard; nonoperative antibiotics are an option for carefully selected uncomplicated cases (with counseling on ~29-40% recurrence/conversion rates)
5. Perforation dramatically worsens prognosis - do not delay workup and surgical consultation