Can We Rule Out Pediatric Appendicitis If Appendix Not Seen on Ultrasound?

July 2, 2024

Written by Samuel Rouleau

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In pediatric patients who have an Alvarado score 6 and below, the absence of free fluid or periappendiceal fat inflammation, when the appendix was not visualized on ultrasound, had a negative predictive value of 99.4% for appendicitis.

Appendix and seek!
The cohort consisted of 1,756 pediatric patients, median age 10.1 years and 57.2% male, who presented to a pediatric ED in Spain with abdominal pain. 579 patients (53.9%) had ultrasounds that visualized the appendix. In those who had appendicitis and ultrasound without view of the appendix, “profuse” free fluid had the highest association with appendicitis (OR 30.9 95% CI 3.8 – 252.7), followed by peri-appendiceal fat inflammation (OR 7.2 95% CI 1.4 – 38), and “little” free fluid (OR 5.0 95% CI 1.7 – 14.6). The researchers found that in patients with an Alvarado Score 6 and below, the absence of the indirect ultrasound findings (free fluid and peri-appendiceal fat inflammation) could exclude appendicitis when the appendix was not visualized. The negative predictive value was 99.4% (95% CI 97.8 – 99.8) with a sensitivity of 84.6% (95% CI 57.8 – 95.7). In those with an Alvarado Score 7 and above, the sensitivity dropped to 66.7 (95% CI 39.1-86.2) with a negative predictive value of 91.5% (95% CI 80.1-96.6).

How will this change my practice?
This is a common clinical conundrum, though this study does not change my practice:

• The main takeaway of this study is that pairing a low pre-test probability for appendicitis (low Alvarado score) with a normal ultrasound that does not visualize the appendix generally rules out appendicitis (assuming there is no free fluid or fat inflammation on the ultrasound).
• This article does not provide a clear answer for patients with a moderate pre-test probability for appendicitis and non-diagnostic ultrasound, which is where I struggle the most. The answer for this situation probably depends on your consultant preferences.
• I would like to see a study that looks prospectively at ultrasound findings combined with laboratory findings to predict the risk for appendicitis, as the current appendicitis scores (Alvarado, pARC, PAS) do not include ultrasound findings. 

Source
Predictive values of indirect ultrasound signs for low risk of acute appendicitis in paediatric patients without visualisation of the appendix on ultrasound. Emerg Med J. 2024 May 10:emermed-2023-213466. doi: 10.1136/emermed-2023-213466. Online ahead of print. PMID: 38729752