This week’s image of the week is brought to us by Dr. Elizabeth Iledare. She confirmed the diagnosis of appendicitis using bedside ultrasound. Ultrasound is being used more frequently in children to make this diagnosis, and it can also be used in our thin adult patients. To perform the exam we use the high frequency linear probe. Ask the patient to point to the location of their pain. In many cases, this will correspond exactly to the location of the abnormal appendix and is the best place to start. From here your want to walk your probe over the entire RLQ, gently compressing the bowel each time you move the probe until you find the appendix. In a normal patient the bowel gas disappears as the abdominal wall muscles above and the psoas muscles beneath are squeezed together. The normal appendix should also compress easily and will appear as a blind ending loop of bowel. Even with practice, a normal appendix can be difficult to find.
In contrast, appendicitis occurs because obstruction of the appendix leads to fluid accumulation, and this is a nidus for infection. An abnormal appendix will appear as a blind-ending tubular structure that is noncompressible and >6mm in diameter.
You may also see an appendicolith, which will look similar to a gallstone- bright white with shadowing beneath (see below), or a loculated fluid collection suggestive of abscess.
If you are interested in learning more, check out the following article that reviews the progression of appendicitis and its appearance on ultrasound.
Chan L, Shin LK, Pai RK, Jeffrey RB.
Ultrasound Q. 2011 Jun;27(2):71-9. Review.