What is the diagnostic approach for appendicitis?

Diagnostic Approach for Appendicitis

The diagnosis of appendicitis should follow a tailored, individualized approach based on disease probability, sex, and age of the patient, using clinical scoring systems to stratify risk and determine the need for imaging studies. 1

Clinical Assessment and Risk Stratification

• The classic presentation of appendicitis includes periumbilical pain migrating to the right lower quadrant, anorexia, nausea, vomiting, and fever, though these symptoms are present in only about 50% of cases 2
• Individual clinical signs and symptoms have low predictive value for appendicitis, necessitating the use of clinical scoring systems 1
• Clinical scoring systems should be used to exclude appendicitis and identify patients at intermediate risk who need imaging diagnostics 1
• The AIR (Appendicitis Inflammatory Response) and AAS (Adult Appendicitis Score) are currently the best performing clinical prediction scores for adults 1
  • AIR score works better for men (cutoff ≤2, specificity 24.7%, failure rate 2.4%) 1
  • AAS score works better for women (cutoff ≤8, specificity 63.1%, failure rate 3.7%) 1

Laboratory Testing

• Laboratory tests and inflammatory serum parameters should always be requested, especially in pregnant patients 1
• White blood cell count, differential with calculation of absolute neutrophil count, and CRP are useful laboratory tests 1
• In pediatric patients, CRP level ≥10 mg/L and leukocytosis ≥16,000/mL are strong predictive factors for appendicitis 1
• The combination of normal white blood cell count and normal CRP, along with other clinical factors, may help exclude acute appendicitis 1

Imaging Based on Risk Stratification

• Low-risk patients according to AIR/Alvarado scores can be discharged with appropriate follow-up without imaging 1, 2
• Intermediate-risk patients benefit most from systematic diagnostic imaging 1, 2
• High-risk patients may proceed directly to surgical consultation rather than diagnostic imaging 1

Imaging Protocol for Adults:

• CT scan is the preferred imaging modality for adults (sensitivity 90-100%, specificity 94.8-100%) 1, 3
• Point-of-care ultrasonography (POCUS) has proven valuable with sensitivity of 91% and specificity of 97% 1
• A conditional CT strategy (CT performed after negative US) reduces CT scans by 50% while maintaining diagnostic accuracy 1

Imaging Protocol for Special Populations:

• In children and women of childbearing age, ultrasound should be the first-line imaging modality 1, 2
• In pregnant patients, MRI shows sensitivity and specificity of 96% 2
• For pediatric patients with inconclusive ultrasound, MRI is preferred over CT as a second-line imaging option 3

Ultrasound Parameters for Diagnosis

• An appendiceal diameter ≥6-7 mm is the most consistent finding in acute appendicitis 4
• Non-compressibility of the appendix with gentle pressure is highly suggestive of inflammation 4
• Pain elicited when pressing on the appendix with the ultrasound probe (sonographic McBurney's sign) is significant 4
• Standardized reporting templates can reduce indeterminate ultrasound results from 44.3% to 13.1% 1, 4

CT Imaging Considerations

• Low-dose CT protocols with intravenous contrast are not inferior to standard protocols in diagnostic accuracy (79% vs. 80%) 1
• CT findings of appendicolith, mass effect, or dilated appendix >13 mm indicate higher risk of treatment failure with antibiotics-first approach 5
• Recent studies show contrast-enhanced low-dose CT is not inferior to standard CT in diagnosing appendicitis or distinguishing between uncomplicated and complicated cases 1

Special Considerations

• Elderly patients have higher rates of perforation (55-70%) and mortality 2
• Mortality varies significantly by severity: non-gangrenous appendicitis <0.1%, gangrenous appendicitis 0.6%, perforated appendicitis approximately 5% 2
• Pregnant patients should not be diagnosed based on symptoms and signs alone; laboratory tests should always be requested 1
• Children may benefit from newer biomarkers such as the Appendicitis Urinary Biomarker (AuB), which has a negative predictive value of 97.6% 1

Common Pitfalls to Avoid

• Relying solely on the Alvarado score to confirm appendicitis is not recommended, as it is not sufficiently specific in adults 1
• Ultrasound accuracy is highly operator-dependent and the appendix may be obscured by bowel gas or difficult to locate in a retrocecal position 4
• Failure to recognize complicated appendicitis may lead to treatment failure and increased morbidity 3
• Overlooking appendicitis in elderly patients, who often present with atypical symptoms and have higher rates of perforation 2