Emergency Physician Bedside Ultrasound for Appendicitis
Why?
To reduce length of stay, improve patient care, and reduce radiation exposure in young patients.
How?
Start with pain medication so you get a better study. (Consider intranasal fentanyl for quicker pain relief and diagnostics in pediatrics.) Study results are also improved with a slim body habitus.
Place the patient supine
Use a high-frequency linear array transducer
Start at the point of maximal tenderness in the RLQ
Transverse and longitudinal planes "graded compression" to displace overlying bowel gas which usually has peristalsis (See Sivitz, et al article for images of "graded compression")
Appendix is usually anterior to the psoas muscle and iliac vein and artery as landmarks
Measure from outer wall to outer wall at the most inflamed portion of the appendix (usually distal end)
Example:
Positive study:
A non-compressible, blind-ending tubular structure in the longitudinal axis >6 mm without peristalsis (see second image above with 8.3 mm diameter measurement)
A target sign in the transverse view (see first image above)
Additional suggestive findings: appendiceal wall hyperemia with color Doppler, appendicoliths hyperechoic (white) foci with an anechoic (black) shadow, periappendiceal inflammation or free fluid
Negative study:
Non-visualization of the appendix with adequate graded compression exam in the absence of free fluid or inflammation.
Limitations for visualization and possible false negative result:
Retrocecal appendix and perforated appendix are difficult to visualize with US.
Pitfalls:
US has good specificity (93% in Sivitz et al article), but limited sensitivity (85% in Sivitz et al article), so trust your clinical judgement. You may need a MRI (pregnant/pediatrics) or CT as they have improved, but not perfect sensitivity.
Valesky, et al. Focus On: Ultrasound for Appendicitis. ACEP Now. June 2012.
Sivitz AB, Cohen SG, Tejani C. Evaluation of Acute Appendicitis by Pediatric Emergency Physician Sonography. Annals of Emerg Med. Oct 2014; 64: 358-363.
