Written by: Morgan McCarthy, MD (NUEM ‘24) Edited by: David Feiger, MD (NUEM ‘22)
Expert Commentary by: Shawn Luo, MD & John Bailitz, MD
Welcome to the NUEM SonoPro Tips and Tricks Series where Local and National Sono Experts team up to take you scanning from good to great for a particular diagnosis or procedure.
For those new to the probe, we recommend first reviewing the basics in the incredible FOAMed Introduction to Bedside Ultrasound Book, 5 Minute Sono, and POCUS Atlas. Once you’ve got the basics beat, then read on to learn how to start scanning like a Pro!
Did you know, appendicitis is one of the most common surgical emergencies. Despite this, some data suggests that appendicitis is missed in 3.8% to 15% of children and 5.9% to 23.5% of adults in ED visits. Appendicitis is difficult to diagnose due to the early nonspecific generalized symptoms (anorexia, generalized pain, nausea, diarrhea or constipation). We can use point of care ultrasound (POCUS) to help evaluate your differential diagnosis. One study showed that after only a 20-minute training ED physicians at various levels of experience were able to scan for appendicitis with a specificity of 97.9% and a sensitivity to 42.8%.
Beyond the classic pediatric patient, who else does the SonoPro scan?
Pocus use for appendicitis is one of the leading diagnostic tools in pediatrics for acute appendicitis. In the pediatric population limiting radiation is generally thought to be of utmost importance. The lack of exposure to radiation and small habitus makes ultrasound a great alternative in the pediatric patient. These tips and tricks can be useful in other high risk adult patients, like pregnant women. It is well known that in adults there is often a higher chance of pathology and surgeons are managing the ultimate say on whether more imaging is necessary. However, the use of ultrasound for acute appendicitis may save time, expedite care, lead to quicker consultation, and potentially augment patient satisfaction and improve outcomes.
How to scan like a Pro:
There are a few ways to scan for the appendix. To start, we recommend simply asking for the patient to point to where the pain is worst and place the probe directly over that spot.
A simple trick is to have the patient cross their right leg over their left leg; this brings the appendix closer to the abdominal wall.
If neither of these work, start to look for visual landmarks to orient yourself: iliac artery and vein, and the psoas muscle. The psoas muscle will be posterior, the iliac artery will be medial and the iliac crest lateral. Many times the appendix may be on top of the iliac artery. ‘Lawn mowing’ the probe up and down in this area may help it come into view.
What to Look For:
Try to look for a blind ending tubular structure that is not undergoing peristalsis. When you locate this, turn your probe to view the appendix in short axis and measure the anterior to posterior diameter. In a normal appendix this may be shorter than the lateral measurements as a normal appendix is compressible!
There are two main criteria for diagnosing appendicitis on ultrasound:
> 6mm*
non-compressible
*Note: Make sure to consider your patient’s age; the criteria may not apply to young children as their appendix may be naturally smaller. Appendix growth typically occurs at 3 to 6 years, therefore in this population you may depend more on secondary findings.
There are many secondary findings that many experts believe may be more useful than the measurements of the appendix itself as this can be very difficult to accurately measure:
What to do next:
Ultrasound for appendicitis is very specific, however not very sensitive. If you see a dilated non-compressible blind ending loop of bowel without peristalsis, you may have identified an appendicitis - call your surgeon, follow recommendations and start antibiotics! If you are uncertain, look for secondary signs of appendicitis as above; if they are found you can increase your suspicion of appendicitis. If these findings are not present, more advanced diagnostic imaging may be required with respect to your clinical suspicion. Consider an MRI in a young patient or CT scan with contrast in an adult for further evaluation.
Where to Learn More (References)
Mahajan P, Basu T, Pai C, et al. Factors Associated With Potentially Missed Diagnosis of Appendicitis in the Emergency Department. JAMA Network Open. 2020;3(3):e200612. doi:10.1001/jamanetworkopen.2020.0612.
Ma, John, et al. Ma and Mateer's Emergency Ultrasound. McGraw-Hill Education, 2020.
Macias, Micheal. TPA, The Pocus Atlas.
Availa, Jacob. 5 minute Sono.
Nelson, Chiricolo, Raio, Theodoro, Patel, Johnson. Can Emergency Physicians Positively Predict Acute Appendicitis on Focused Right Lower Quadrant Ultrasound?. Annals of Emergency Medicine, 2005; 46: 27-28
Expert Commentary
Excellent job by Morgan and David on this engaging and informative post summarizing the latest and greatest pro-tips and tricks for POCUS for Appendicitis. POCUS again has been demonstrated to be a helpful adjunct to improve time to diagnosis and treatment when utilized by trained clinicians for appropriate patients. On your next pediatric, pregnant, or otherwise thin “Rule out Appy”, begin the exam by asking the patient to cross their leg to flex the psoas muscle to bring the appendix closer to probe. Have the patient point to the pain to identify where to start. If the appendix is not visualized, then go to McBurney’s point in the axial plane, visualizing the iliac artery & vein to find the nearby appendix. Next, start “lawn mowing” by compressing slowly but with adequate depth to displace bowel gas. Once you see what appears to be an inflamed appendix, trace the structure to verify the blind-ending and hold your probe for a few seconds to confirm the lack of peristalsis. Measure the diameter, then turn on color flow and look for other secondary signs of inflammation. Since the specificity is high, when appendicitis is visualized, call your surgeon, and consider skipping the CT. But remember, since the appendix often “hides” within the bowel the sensitivity is low, so other comprehensive imaging will be needed to reach the correct diagnosis.
John Bailitz, MD
Vice Chair for Academics, Department of Emergency Medicine
Professor of Emergency Medicine, Feinberg School of Medicine
Northwestern Memorial Hospital
Shawn Luo, MD
PGY4 Resident Physician
Northwestern University Emergency Medicine
How To Cite This Post:
[Peer-Reviewed, Web Publication] McCarthy, M. Feiger, D. (2021, Nov 22). Sono Pro Tips and Tricks for Acute Appendicitis. [NUEM Blog. Expert Commentary by Luo, S and Bailitz, J]. Retrieved from http://www.nuemblog.com/blog/sonopro-tips-and-tricks-for-acute-appendicitis
