This week’s Image of the Week features images from two patients. The first seen by Dr’s Meloy and Sizemore, then second by Dr’s Shah and Middlebrooks. Both presented with right lower quadrant pain. Take a look at the images and see if you can identify the pathology.
Both of these patients were diagnosed with appendicitis. In the videos for the first patient the operator measures the diameter of the appendix as 9.7 mm, which is enlarged. In the video from the second patient you can see both transverse and longitudinal views of the appendix. In transverse it appears as a circular, target-like structure. In longitudinal it is seen as a blind-end tube. In both views the operator applies compression with the ultrasound probe which does not cause collapse of the structure. To evaluate a patient in which you suspect appendicitis, place the probe in the right lower quadrant at the point of maximal tenderness and then pan looking for a blind-ended tubular structure as seen in the images. If one is found the diameter should be measured and pressure should be applied to assess for compressibility. Findings suggestive of appendicitis include:
- aperistaltic, noncompressible, dilated appendix ( >6 mm outer diameter)
- appendicolith (white with distal shadowing)
- distinct appendiceal wall layers
- echogenic prominent pericaecal fat (bright white on ultrasound)
- periappendiceal fluid collection
- target appearance (on axial section)
When using bedside ultrasound, it is important to understand the limitations of the modality. Both the sensitivity and specificity have high reported variability in the literature, though the largest meta-analysis reported them as 88% and 94% respectively in the pediatric population and 83% and 93% in the adult population. This is highly dependent on operator skill. In many patients it may be difficult to identify the appendix on ultrasound secondary to patient habitus, anatomy, or bowel gas, particularly if the appendix is normal. If your patient has a concerning presentation coupled with ultrasound findings suggestive of appendicitis, you should be consulting your surgeon and can likely spare that patients from the radiation exposure of a CT scan. However, if you are unable to identify the appendix on ultrasound but are concerned by the history and exam further evaluation with CT should be obtained. Ultrasound should be considered the first line diagnostic modality in the pediatric population as well as in pregnant patients.
References:
- Puylaert JB. Acute appendicitis: US evaluation using graded compression. Radiology. 1986; 158 (2): 355-60.
- Doria AS et al. US or CT for diagnosis of appendicitis in children and adults? A meta-analysis. Radiology. 2006; 241(1):83.
Thanks for all your great images this week! Happy Scanning!
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Eric Deutsch
Department of Emergency Medicine
Emory University SOM
