Epidemiology and Management of Appendicitis in Adults
Epidemiology
Acute appendicitis affects 96.5 to 100 adults per 100,000 population annually, with a lifetime risk of 8.6% in males and 6.7% in females, making it the most common abdominal surgical emergency worldwide. 1, 2, 3
Age and Gender Distribution
- The peak incidence occurs between ages 10-20 years, though appendicitis can occur at any age 3
- After adolescence, incidence decreases with advancing age 4
- Among patients presenting with acute abdominal pain in the Emergency Department, approximately 15% of patients older than 50 years will have appendicitis, compared to nearly 30% of younger patients 4
Special Considerations in Elderly Patients
- Elderly patients (>65 years) experience significantly higher mortality rates of 8% compared to 0-1% in younger patients 4
- Complicated appendicitis with perforation or abscess occurs in 18-70% of elderly patients versus 3-29% in younger populations 4
- The case fatality rate after appendectomy increases threefold for each decade of age, reaching more than 16% in nonagenarians 4
- Diagnostic accuracy is lower in elderly patients (64%) compared to younger age groups (78%) 4
- Time from symptom onset to admission and from admission to surgery is consistently longer in elderly patients 4
Diagnostic Approach
Clinical Evaluation
A constellation of characteristic right lower quadrant pain, localized abdominal tenderness, and laboratory evidence of acute inflammation identifies most patients with suspected appendicitis, though no single clinical finding is unequivocal. 4
Key Clinical Features
- Classic presentation includes vague periumbilical pain, anorexia/nausea/intermittent vomiting, migration of pain to the right lower quadrant, and low-grade fever 1
- This classic presentation leads to correct diagnosis in approximately 90% of cases 1
- Right lower quadrant pain, abdominal rigidity, and periumbilical pain radiating to the right lower quadrant are the best signs for ruling in appendicitis in adults 2
Clinical Scoring Systems
- The AIR (Appendicitis Inflammatory Response) score or AAS (Adult Appendicitis Score) should be used in adults for risk stratification, as these have the highest discriminating power 5
- The Alvarado score should NOT be used alone to confirm appendicitis in adults due to insufficient specificity, though it helps exclude the diagnosis 5
- These scores effectively identify low-risk patients who can avoid imaging and hospital admission, while flagging intermediate-risk patients who need diagnostic imaging 5
Laboratory Testing
Obtain WBC with differential and CRP immediately in all patients, as the combination of WBC >10,000/mm³ AND CRP ≥8 mg/L has a positive likelihood ratio of 23.32 for appendicitis. 6, 5
- Elevated WBC count (>10,000/mm³) alone has limited diagnostic value with a positive likelihood ratio of only 1.59-2.7 5
- C-reactive protein ≥10 mg/L has a positive likelihood ratio of 4.24 5
- The combination of elevated WBC and left shift has a positive likelihood ratio of 9.8 5
Imaging Strategy
Helical CT of the abdomen and pelvis with intravenous contrast (without oral or rectal contrast) is the recommended imaging procedure for adults with suspected appendicitis, achieving sensitivity of 96-100% and specificity of 93-95%. 4, 6, 1
CT Imaging Specifications
- IV contrast alone is sufficient and strongly preferred, increasing sensitivity to 96% 6, 5
- Oral contrast is unnecessary and may delay diagnosis 6, 5
- CT reduces negative appendectomy rates from historical 14.7% to current 1.7-7.7% 5
Special Population Considerations
All female patients of child-bearing potential should undergo pregnancy testing prior to imaging. 4
- Pregnant patients in the first trimester should undergo ultrasound or MRI without IV contrast instead of CT 4, 6
- Ultrasound has sensitivity of 76% and specificity of 95% in general populations 6, 5
- MRI achieves sensitivity of 94% and specificity of 96% for acute appendicitis 6, 5
- If ultrasound is inconclusive in pregnant patients, MRI without IV contrast is preferred over CT 6, 5
Management of Equivocal Imaging
- For patients with negative imaging but persistent clinical suspicion, follow-up at 24 hours is mandatory due to low but measurable false-negative rates 4, 6
- Patients with suspected appendicitis that cannot be confirmed or excluded by imaging require careful follow-up and may be hospitalized if clinical suspicion is high 4
Management
Antibiotic Therapy
Antimicrobial therapy should be administered to all patients who receive a diagnosis of appendicitis, using agents effective against facultative and aerobic gram-negative organisms and anaerobic organisms. 4
Antibiotic Regimens
- Acceptable regimens include piperacillin-tazobactam monotherapy, or combination therapy with cephalosporins or fluoroquinolones plus metronidazole 6, 1
- Other options include aminoglycoside-based regimens, carbapenem monotherapy, or beta-lactam/beta-lactamase inhibitor combinations 7
- For patients with severe beta-lactam allergies, ciprofloxacin plus metronidazole can be used 7
Duration of Antibiotic Therapy
- For acute, nonperforated appendicitis, prophylactic antibiotics should be discontinued within 24 hours of surgery 4
- For patients with equivocal imaging receiving empiric antibiotics, treatment should continue for a minimum of 3 days until clinical symptoms resolve or a definitive diagnosis is made 4
Surgical Management
Both laparoscopic and open appendectomy are acceptable procedures, with operative intervention performed as soon as reasonably feasible once diagnosis is established. 4, 6
Timing of Surgery
- Surgery may be deferred for a short period according to individual institutional circumstances 4
- For complicated appendicitis, surgery should be performed within 24 hours 7
- For uncomplicated cases, surgery within 8 hours is recommended 7
Approach Selection
- Use of laparoscopic versus open approach should be dictated by surgeon's expertise 4
- Laparoscopic appendectomy is the preferred approach when expertise is available 7, 1
Nonoperative Management
In highly selected patients with uncomplicated acute appendicitis without appendicolith on imaging, an antibiotics-first strategy can be considered as an alternative to surgery, with success rates of approximately 63-73% at one year. 6, 8, 1
Patient Selection for Antibiotics-First Approach
- CT findings of appendicolith, mass effect, or dilated appendix >13 mm are associated with higher treatment failure rates (≈40%) 1
- Surgical management should be recommended in patients with these high-risk CT findings who are fit for surgery 1
- In patients without high-risk CT findings, either appendectomy or antibiotics can be considered as first-line therapy 1
Outcomes of Antibiotic Therapy
- After one year of follow-up, 63-73% of patients treated with antibiotics remain asymptomatic without complications or recurrences 8, 1
- The overall incidence of complications is 18% in the antibiotic group versus 25% in the immediate appendectomy group 8
- Optimal outcome at one year occurs in 73% of antibiotic-treated patients versus 97% of patients with immediate appendectomy 8
Management of Complicated Appendicitis
Patients with perforated appendicitis should undergo urgent intervention to provide adequate source control. 4
Abscess Management
- Patients with a well-circumscribed periappendiceal abscess should be managed with percutaneous drainage when feasible, with appendectomy generally deferred 4, 6, 7
- Percutaneous drainage plus antibiotics achieves efficacy rates of 70-90% with lower complication rates 7
- Approximately 80% of patients successfully treated with percutaneous drainage do not require subsequent appendectomy 7
Phlegmon Management
- Selected patients presenting several days after symptom onset with a periappendiceal phlegmon or small abscess not amenable to drainage may delay or avoid source control procedures 4
- Such patients are treated with antimicrobial therapy alone 4
Management of Treatment Failure
In patients with persistent or recurrent clinical evidence of intra-abdominal infection after 4-7 days of therapy, CT or ultrasound imaging should be performed while continuing antimicrobial therapy. 4, 6
- Extra-abdominal sources of infection and noninfectious inflammatory conditions should be investigated if the patient is not responding to microbiologically adequate therapy 4
- For patients who do not respond initially with a persistent focus of infection, both aerobic and anaerobic cultures should be obtained from at least 1.0 mL of fluid or tissue transported in an anaerobic system 4
Clinical Pathways and Quality Improvement
Local hospitals should establish clinical pathways to standardize diagnosis, in-hospital management, discharge, and outpatient management of appendicitis. 4
- Pathways should be designed by collaborating clinicians including surgeons, infectious diseases specialists, emergency medicine physicians, radiologists, nursing providers, and pharmacists 4
- Pathways should reflect local resources and local standards of care 4
Common Pitfalls and Caveats
Diagnostic Pitfalls
- Clinical scoring systems alone should never be used to confirm appendicitis—they must be combined with imaging in intermediate-risk patients 5
- Low or incomplete Alvarado scores do not reliably exclude appendicitis—studies show 8.4% of patients with appendicitis had scores below 5 5
- Ultrasound accuracy is highly operator-dependent, and both MRI and ultrasound may incorrectly classify up to half of patients with perforated appendicitis as having simple appendicitis 5
Management Pitfalls
- Proceeding directly to surgery without imaging in patients with incomplete clinical findings risks unnecessary surgery and missing alternative diagnoses 5
- Negative appendectomy carries long-term morbidity and should be avoided through appropriate imaging 5
- In elderly patients, atypical presentations are common and diagnostic delays contribute to higher perforation rates and mortality 4