The bedside evaluation for appendicitis can be so satisfying! It is one of the more difficult applications however, and like most ultrasound scans, it is operator and habitus dependent, but it can never hurt to try and look! First, ask the patient to point to where it hurts the most and begin there. Use the linear high frequency probe for the pediatric/thinner patients and the curvilinear low frequency probe for the larger body habitus patients. Adjust/Increase your depth in order to see past the peritoneal lining and use a graded compression technique in the RLQ and its surrounding area, with the indicator pointed toward the patient's right side. Steady graded compression can help displace bowel gas that can obscure your image. This will be the transverse view of the cecum and appendix.
The sonographic criterion for diagnosis is visualization of a noncompressible circular structure that may have bowel wall edema (don't mistake it for the lymph node and don't forget to look for free fluid around the area as well!). In the longitudinal view (by turning your probe 90 degrees and differentiating it from a lymph node) a blind--ended noncompressible tubular structure without peristalsis is seen with appendicitis. It can be found by landmarking between the psoas muscle and iliac vessels. The diameter of the appendix will be larger than normal (>6mm) and you may see a thickened wall, peri--appendiceal fluid and occasionally an appendicolith (like the image here!).
Some pitfalls are when the terminal ileum is misinterpreted as the appendix and being unable to locate the appendix ("US equivocal"). If you aren't able to find the appendix, then of course it can't be ruled out and if your level of suspicion is high, consider further imaging or a surgical consultation (especially in pediatrics). However, if it is a low risk patient, consider an observation period since many of the CT scans we order (about 80%) to evaluate the "US equivocal" findings are negative. appendicolith Iliacs as landmarks Because this is the last Scanner of the Month for the year we also want to give a shout out and extra congratulations to all of you for really fantastic scanning this year and our incredible prior Scanners of the Month: Brianne Steele, Kyle Drullinger, Dave Johnson, Eric Ladd, Jeff Huang, and Margie Teng. You all make our QA and ultrasound teaching job SO fun and worthwhile!