From the Guidelines
Ultrasound is not always diagnostic in pediatric acute appendicitis due to its limited accuracy in distinguishing between perforated and nonperforated appendicitis, as well as technical challenges and patient factors that can affect its sensitivity and specificity. The diagnostic accuracy of ultrasound is highly operator-dependent and can be limited by patient factors such as obesity, bowel gas, pain limiting compression, or an appendix in an atypical location 1. Technical challenges include difficulty visualizing a normal appendix (which would rule out appendicitis) or a retrocecal appendix. According to the American College of Radiology, ultrasound has been shown to have limited accuracy in the distinction of perforated from nonperforated acute appendicitis 1.
In cases where ultrasound is non-diagnostic but clinical suspicion remains, additional imaging with CT or MRI may be necessary. CT offers higher sensitivity (94-98%) but exposes children to radiation, while MRI provides excellent soft tissue contrast without radiation but has limited availability, longer scan times, and higher costs 1. The clinical assessment remains crucial, and serial examinations combined with laboratory markers like white blood cell count and C-reactive protein can help guide management when imaging is inconclusive. The American College of Radiology recommends that the initial consideration for imaging in a child with suspected acute appendicitis is based on clinical assessment, which can be facilitated with published scoring systems, and that the level of clinical risk and the clinical scenario define the need for imaging and the optimal imaging modality 1.
Some key points to consider when evaluating a child with suspected acute appendicitis include:
- The incidence of appendicitis peaks during adolescence and is uncommon in infants and preschool children and rare in newborns 1
- The diagnosis of acute appendicitis often presents a challenge, as the classic presenting symptoms are not always elicited and are only moderately reproducible between clinicians 1
- Imaging has been shown to facilitate management and decrease the rate of negative appendectomies in children with suspected acute appendicitis 1
- Nonoperative treatment of early, uncomplicated appendicitis is increasingly being explored, and imaging plays a role in identifying candidates for nonoperative management 1
From the Research
Ultrasound Limitations in Diagnosing Pediatric Acute Appendicitis
- Ultrasound (US) is often used as the primary imaging modality in pediatric patients with suspected acute appendicitis due to concerns about radiation exposure from computed tomography (CT) scans 2, 3, 4.
- However, the diagnostic accuracy of US in pediatric acute appendicitis is limited, with sensitivity, specificity, and accuracy of 55.6%, 85%, and 71%, respectively, as reported in one study 2.
- The use of a standardized ultrasound scoring system, such as the Pediatric Ultrasound Appendicitis Score, may improve the diagnostic accuracy of US, with reported sensitivity and specificity of 90.2% and 90%, respectively, for scores of 7 or more 3.
- Despite these efforts, US may not be diagnostic in all cases of pediatric acute appendicitis, and additional imaging modalities, such as CT or magnetic resonance imaging (MRI), may be necessary in equivocal cases 2, 5, 6.
Alternative Imaging Strategies
- A stepwise imaging approach that begins with graded compression US and proceeds to CT or MRI in select cases is currently considered best practice for diagnosing pediatric appendicitis 6.
- MRI, in particular, has been shown to be highly sensitive and specific in the evaluation of children with acute right lower quadrant pain, without the use of ionizing radiation or contrast 5.
- However, the accessibility and cost of MRI may limit its more widespread use as a primary imaging modality 5.