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Reference - Acad Emerg Med 2017 May;24(5):578 (level 2 [mid-level] evidence)
- For suspected acute appendicitis in adults, computed tomography (CT) imaging may be performed before appendectomy to reduce diagnostic uncertainty, but faster assessments without radiation, such as with bedside point-of-care ultrasound (POCUS) in the emergency department, may further improve care.
- A diagnostic cohort study assessed the diagnostic performance of bedside POCUS conducted by emergency physicians experienced with POCUS in 264 adults with suspected acute appendicitis.
- POCUS imaging plus clinical assessment had high diagnostic specificity (95.8%), positive predictive value (97.5%), and positive likelihood ratio (21.9), suggesting that it can rule in acute appendicitis in adults if conducted by properly trained operators. However, POCUS alone should not be used to rule out appendicitis.
Acute appendicitis can be difficult to distinguish from other causes of abdominal pain based on clinical presentation alone. Urgent appendectomy is the mainstay of treatment, but it is also important to avoid unnecessary surgery. CT imaging is often performed before surgery to reduce diagnostic uncertainty, but faster assessments without radiation may further improve care (BMJ 2017 Apr 19;357:j1703, N Engl J Med 2015 May 14;372(20):1937). Investigations have indicated that bedside POCUS may have good diagnostic performance in some cases, but studies have varied in quality and inconsistencies in timing of imaging and operator specialty make it unclear under what conditions it should be considered (Acad Emerg Med 2017 May 2 early online, Insights Imaging 2016 Apr;7(2):255). To assess bedside POCUS conducted in the emergency department (ED), a recent diagnostic cohort study investigated 264 adults (mean age 30 years, 57% men) presenting to the ED with abdominal pain and suspected acute appendicitis. An additional 16 patients were enrolled but were lost to follow-up and excluded from analyses. Bedside POCUS was conducted by 1 of 8 emergency physicians with ≥ 5 years experience with ultrasound, who had additional training for diagnosing appendicitis, and who were aware of the study’s aims. The emergency physician then recorded a diagnosis based on clinical history, physical exam, and POCUS imaging, with appendicitis indicated by an aperistaltic and noncompressible tubular structure > 6 mm diameter located at the right lower quadrant. The patients were subsequently assessed with radiologist-performed ultrasound by experienced residents who were not aware of study aims, and patients had abdominal CT scans if there was diagnostic uncertainty. Ultimate management decisions were made by the consulting general surgeon.
Acute appendicitis was diagnosed in 169 patients (64%) using the reference standard of intraoperative findings, pathology results, or, in patients who did not have surgery, negative findings on CT or symptom relief during 30-day follow-up. For diagnosing appendicitis, bedside POCUS had a specificity of 95.8%, a positive predictive value of 97.5%, a positive likelihood ratio of 21.9, a sensitivity of 92.3%, a negative predictive value of 87.5%, and a negative likelihood ratio of 0.08.
The high specificity, positive predictive value, and positive likelihood ratio reported in this study suggest that bedside POCUS administered by an experienced emergency physician plus clinical assessment can rule in acute appendicitis in adults. Although the sensitivity was also high, given the potentially severe complications of untreated appendicitis, POCUS alone should not be used to rule out appendicitis. It is important to emphasize that, although ultrasound was conducted in the ED, ultrasound image quality is dependent on operator skill and the operators in this study were experienced and had additional training for diagnosing appendicitis. These results, therefore, are limited to these situations and may not apply to other operators. Also, body mass index may affect imaging quality (AJR Am J Roentgenol 2007 Feb;188(2):433) but was not reported in this study, so it is not known whether or not these results apply to patients within a limited BMI range. Finally, direct comparisons to radiologist-conducted ultrasound or CT imaging cannot be made, as the radiologists did not have additional training and CT imaging was not conducted in all patients. However, if properly trained operators are available, POCUS may be considered for detecting acute appendicitis in adults.
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