Diagnostic Approaches for Appendicitis

Evidence-Based Diagnostic Approaches

The American College of Emergency Physicians and American College of Radiology recommend using validated clinical scoring systems rather than individual clinical signs 1, 2, 3
Rebound tenderness and guarding are important physical examination findings that suggest peritoneal irritation 4

The American College of Emergency Physicians recommends using the AIR (Appendicitis Inflammatory Response) score, which is currently one of the best performing clinical prediction scores 5
The AAS (Adult Appendicitis Score) has high discriminating power in adults with suspected appendicitis 5
The Alvarado score is useful for excluding appendicitis but not sufficiently specific for confirming it 5

White blood cell count with differential calculation of absolute neutrophil count is a useful laboratory test 4
CRP (C-reactive protein) is an important inflammatory marker, especially in pediatric patients 5
Both elevated WBC count and left shift together have a positive likelihood ratio of 9.8 4
Normal WBC and CRP have high negative predictive value 5

The American College of Radiology recommends ultrasound as first-line imaging, especially in children and pregnant women 6
CT with intravenous contrast is recommended when ultrasound is inconclusive or negative but clinical suspicion remains high 6
MRI is an alternative to CT, particularly in pregnant patients or those with contrast allergies 1, 6

Relying on non-validated clinical signs can lead to missed diagnoses 2, 3
Atypical presentations are common, especially in elderly patients 4, pregnant women 5, children 5, and patients with retrocecal or pelvic appendix position 7

Apply validated clinical scoring systems (AIR or AAS score) to stratify risk 5
For intermediate-risk patients, perform ultrasound as first-line imaging 6
For high-risk patients or inconclusive ultrasound, proceed to CT with IV contrast 6
In pregnant patients or those with contrast allergies, consider MRI instead of CT 1, 6

The Pediatric Appendicitis Score (PAS), which includes the hop test, has been validated in multiple studies and is recommended by major guidelines for risk stratification in children with suspected appendicitis, with a sensitivity of 80.3% for appendicitis in children 8, 9
Validated clinical scoring systems (AIR score, AAS score in adults; PAS or AIR score in children) that incorporate peritoneal signs including the hop/skip test should be used to decrease negative appendectomy rates and reduce unnecessary imaging in low-risk patients 8, 9

Clinical scores alone are sufficiently sensitive to exclude appendicitis and identify low-risk patients who may not need imaging, with the hop test being a valuable component of these scores 8, 9
The hop test should be documented alongside other peritoneal signs such as rebound tenderness, guarding, psoas sign, and obturator sign, and combined with laboratory markers (WBC with differential, CRP) and validated clinical scores 8, 9

Low-risk patients (low clinical scores with negative hop test) can be considered for discharge without imaging, while intermediate-risk patients should proceed to ultrasound as first-line imaging regardless of hop test result 8, 9
The presence of positive peritoneal signs (including hop test) increases the likelihood of appendicitis and helps justify imaging or surgical intervention, with high-risk patients (high clinical scores with positive hop test) proceeding to CT or surgical consultation 8, 9

The American College of Radiology recommends proceeding to ultrasound as first-line imaging in intermediate-risk patients, regardless of Rovsing sign result, and if ultrasound is nondiagnostic or equivocal, proceeding directly to CT abdomen and pelvis with IV contrast (sensitivity 90-100%, specificity 94.8-100%) 10, 11

In children, staged ultrasound followed by CT if needed achieves 99% sensitivity and 91% specificity, although the exact citation for this statistic is not provided, a similar approach is supported by the Journal of the American College of Radiology 11