Appendicitis ACEP Clinical Policy

Author: Michelle Lin, MD
Updated: 6/18/2010

Appendicitis: ACEP Clinical Policy

How predictive is WBC in appendicitis?

WBC count > 10K and likelihood of having appendicitis:

Alvarado Score

Alvarado score in predicting appendicitis (Max 10 points)

Symptom or sign Point(s)
Pain migration 1
Anorexia-acetone in urine 1
Nausea/vomiting 1
RLQ tenderness 2
Rebound pain 1
Temperature > 37.3C oral 1
WBC > 10K 2
Left shift WBC (>75% PMN) 1


  • 1-4 (appendicitis unlikely)
  • 5-6 (possible)
  • 7-8 (probable)
  • 9-10 (very probable)

However, 0-8% of patients with Score < 5 had appendicitis

Beware of patients <10 yr and >60 yr old for atypical presentations

CT imaging

IV contrast improves ability to detect appendicitis (Jacobs, Radiology 2001)

CT with... Sensitivity
PO/IV contrast 91%
PO contrast only 76%

Addition of oral contrast to CT Abd-pelvis (IV contrast) study is unnecessary (Anderson, Am J Surg 2005)

CT Technique Sens Spec
Noncontrast 93% 98%
PO/IV contrast 93% 93%
Rectal contrast 97% 97%

Imaging in Pediatric Appendicitis

Ultrasound: Appendix >6 mm in diameter, non-compressible appendix, appendiceal tenderness

  • Positive LR 17.2-49.5
  • Negative LR 0.01-0.14

CT: Unclear about additional benefit of PO/IV contrast. Many give PO/IV because ofless intraperitoneal fat in children (less obvious stranding on noncontrast study)

Kharbanda, Pediatrics 2005: In kids, if 0/5 of the following criteria, then the patient is very unlikely to have appendicitis (negative LR=0.058):

  1. Nausea
  2. Right lower quadrant pain
  3. Difficulty walking
  4. Rebound tenderness
  5. Absolute PMN>6,750 (* see Fagan nomogram)

Fagan nomogram

Fagan nomogram

Draw a connecting your pre-test probability and your likelihood ratio. This provides you with your post-test probability.


  • Howell JM, Eddy OL, Lukens TW, Thiessen ME, Weingart SD, Decker WW; American College of Emergency Physicians.Clinical policy: Critical issues in the evaluation and management of emergency department patients with suspected appendicitis. Ann Emerg Med. 2010 Jan;55(1):71-116. [PubMed]