MRI is as good as CT at confirming or ruling out acute appendicitis in children, teens and adolescents, and it doesn’t matter whether the reading radiologist is specialized in abdominal or pediatric practice.

So conclude the authors of a study conducted at the University of Wisconsin and published online Aug. 10 in the American Journal of Roentgenology.

Sonja Kinner, MD, Scott B. Reeder, MD, PhD, and colleagues prospectively enrolled 48 patients between 12 and 20 years old who presented in the emergency department with nontraumatic abdominal pain.

The patients were imaged with both modalities with or without contrast, depending on the institution’s routine age-based contrast protocols.

Fellowship-trained abdominal and pediatric radiologists blinded to clinical outcomes reviewed the exams in randomized order. The readers rated likelihood for appendicitis from 1 (definitely not appendicitis) to 5 (definitely appendicitis).

Analyzing the ratings, the researchers found no statistically significant difference in accuracy between imaging modality or radiologist subspecialty.

Sensitivity and specificity were 85.9 percent and 93.8 percent for unenhanced MRI, 93.6 percent and 94.3 percent for contrast-enhanced MRI, and 93.6 percent and 94.3 percent for CT.

On-par accuracy

Further, although pediatric radiologists showed improved sensitivity and specificity compared with abdominal radiologists when using only unenhanced MRI, there was substantial agreement between abdominal and pediatric radiologists for all methods (κ = 0.72–0.83).

Additionally, interpretation times were closely similar between the two subspecialties.

From these findings, Kinner and colleagues conclude that MRI’s accuracy for diagnosing acute appendicitis is “very similar” to CT.

In their discussion, the authors point out that, apart from diagnostic accuracy and interreader agreement, each imaging modality has its pros and cons.

Contrast-enhanced CT and contrast-enhanced MRI require IV access, for example, while an unenhanced MRI “can be performed without this burden, which can be beneficial in an already anguished pediatric patient,” they write.

“MRI (unenhanced or contrast-enhanced), on the other hand, is often not as readily available as CT, but CT carries the burden of radiation exposure,” they add. “Therefore, we believe that these advantages and disadvantages favor MRI, especially unenhanced MRI.”

What about ultrasound?

Kinner and colleagues also take up the question of whether abdominal ultrasound might not often be the better radiation-free choice.

They note that the American College of Radiology Appropriateness Criteria for right lower quadrant pain—i.e., suspected appendicitis—calls for ultrasound as the go-to imaging modality for evaluating children under 14 who present with such pain.

“Unlike MRI, ultrasound has the benefit of being widely available and has lower associated charges,” Kinner et al. write.

However, they note, ultrasound’s widespread adoption for this indication “has been hindered by its highly variable performance caused by variation in the technical skills of sonographers as well as patient habitus and ability and willingness to lie still.”