What is the role of ultrasonography in the workup of pediatric appendicitis?

Updated: Oct 25, 2018
  • Author: Adam C Alder, MD; Chief Editor: Carmen Cuffari, MD  more...
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Answer

Given the potential risks of radiation from CT scans, graded compression ultrasonography may be the preferred initial imaging modality in the evaluation of pediatric acute appendicitis. This technique involves locating the appendix and then attempting to compress its lumen.

For ultrasonography to be diagnostic of appendicitis, the operator must visualize the appendix. Even if the appendix is not visualized, however, appendicitis can be excluded more confidently if ultrasonography shows no secondary signs of appendicitis (eg, hyperechoic mesenteric fat, fluid collection, localized dilated small bowel loop). [4, 5]

A positive finding is a noncompressible tubular structure 6 mm or wider in the RLQ (see the images below). This structure is tender during palpation with the ultrasonographic probe. Additional supportive findings include an appendicolith, fluid in the appendiceal lumen, focal tenderness over the inflamed appendix (sonographic McBurney point), and a transverse diameter of 6 mm or larger. In patients with a perforated appendix, ultrasonography may reveal a periappendiceal phlegmon or abscess formation.

Ultrasonographic examination of the right lower qu Ultrasonographic examination of the right lower quadrant reveals a greater than 6-mm noncompressible tubular structure shown in cross section. Discomfort was noted as the probe was depressed over this structure. A small amount of free fluid is also noted surrounding the appendix.
Ultrasonographic examination of the right lower qu Ultrasonographic examination of the right lower quadrant reveals a greater than 6-mm noncompressible tubular structure shown in cross section. Discomfort was noted as the probe was depressed over this structure. A small amount of free fluid is also noted surrounding the appendix.

Abdominal ultrasonography has proved to be valuable for diagnosing appendicitis in children, with most published reports indicating a sensitivity, specificity, and accuracy of at least 90-95%. Furthermore, some authors have found that ultrasonography is more sensitive and specific than clinical impression and increases diagnostic accuracy when used either alone or in conjunction with laboratory results. [6]

The advantages of ultrasonography include its noninvasiveness, lack of radiation, no contrast medium, and minimal pain. The downside of ultrasonography is that the examination is operator dependent and may not be available at some institutions. Factors that add difficulty to the examination include obesity and gaseous distention of the intestines overlying the appendix. However, results of one study determined that ultrasonography should continue to be the first diagnostic imaging study in suspected appendicitis, regardless of the child's body mass index (BMI). [7]

Ultrasonography is also useful in diagnosing alternative pathologies (eg, tubo-ovarian abscess, ovarian torsion, ovarian cyst, mesenteric adenitis).

A prospective study by Lowe et al comparing noncontrast CT scanning and ultrasonography revealed a sensitivity, specificity, and accuracy of 97%, 100%, and 98%, respectively, for unenhanced CT scanning, compared to 100%, 88%, and 91%, respectively, for ultrasonography. [8] Still others have shown that the perforation rate and negative appendectomy rate can be decreased by using both tests in tandem.

A study assessed the outcomes in the change of preference in imaging modalities from computed tomography (CT) to ultrasonography (US) due to concerns about ionizing radiation exposure. The study reported that among children with suspected appendicitis, the use of US imaging has increased substantially as the use of CT has declined. Despite the increased reliance on the diagnostically inferior US, important condition-specific quality measures, including the frequency of appendiceal perforation and ED revisits, remained stable, and the proportion of negative appendectomy declined slightly. [9]  Another study by Nicole et al showed a high proportion of inconclusive examinations from point-of-care ultrasounds to detect appendicitis in a pediatric emergency department. [25]

 

For more information, see the Medscape Reference article Appendicitis Imaging.


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