Using limited-range CT for children with suspected appendicitis reduces dose while maintaining accuracy

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 - radiation dose, CT

Limited-range CT exams performed from the top of L2 to the top of the pubic symphysis are as accurate as full-range CT in children with suspected appendicitis and reduces the radiation dose by 46 percent, according to a new study published in the American Journal of Roentgenology.

Lead author Michael T. Corwin, MD, UC Davis Medical Center in Sacramento, California, and colleagues studied data from 210 pediatric patients who all underwent abdominopelvic CT for suspected acute appendicitis from December 2012 to December 2014. Two radiologists reviewed the exams of each patient, looking first at just the limited scans from the top of the L2 vertebral body to the top of the pubic symphysis and then at the full scan. Was the appendix visualized in the limited scans? If radiologists only had limited scans to use, would that be enough to make the right diagnosis?

Overall, the appendix was visualized in every patient’s limited scan. None of the 58 cases of acute appendicitis were missed with the limited scan when compared to the full scan. Radiation was reduced by approximately 46 percent, a significant difference.

“The results of our study show that a limited-range CT scan prescribed from the superior endplate of L2 to the top of the pubic symphysis is as accurate as a full abdominopelvic CT scan in the diagnoses of acute appendicitis in children,” the authors wrote. “The use of bony landmarks on the localizer radiograph allows reproducible prescription of a scan that reduces the radiation dose by nearly 50 percent. This method is simple to implement and applicable across different vendor platforms.”

One case of hydronephrosis and one of acute acalculous cholecystitis were missed with the limited scans. However, the authors noted, ultrasound is considered the “first-line modality” for detecting both conditions.

“Institutions adopting a limited-range CT protocol may consider a more complete abdominal ultrasound protocol instead of a localized study to the right lower quadrant to ensure evaluation of the upper abdominal organs,” the authors wrote. “In addition, the patient can be brought back for scanning of the upper abdomen if a partially visualized finding needs further imaging.”

Corwin et al. noted that the study had limitations. It was a single-center study, for instance, and the CT protocol used was “not entirely uniform with respect to use of oral and rectal contrast agent.” They also added that MR exams are another option for diagnosing appendicitis, and they include no ionizing radiation.