AJR: Low-dose, unenhanced CT effective for appendicitis evaluation

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Patients with possible appendicitis are typically evaluated using a standard-dose contrast-enhanced CT, but a low-dose unenhanced CT that delivers approximately 50 percent less radiation is just as effective, according to a study in the July issue of the American Journal of Roentgenology.

Hyobin Seo, MD, and colleagues from the Seoul National University College of Medicine in Seoul, South Korea, compared low-dose unenhanced CT with standard-dose contrast-enhanced CT in the diagnosis of appendicitis.

Researchers reported that the standard-dose enhanced CT scan delivers approximately 8 mSv of radiation; the low-dose unenhanced CT scan delivers approximately 4.2 mSv of radiation.

The investigators said that 207 adults with suspected appendicitis underwent CT with mean effective doses of both 4.2 and 8 mSv. They rated the likelihood of appendicitis and appendiceal visualization on five- and three-point scales, respectively, and proposed alternative diagnoses.

Seo and colleagues said that a total of 78 patients with appendicitis were evaluated using both the standard-dose and low-dose methods. Two radiologists retrospectively reviewed CT images. Radiologist One correctly identified appendicitis in 77 out of 78 patients using the low-dose unenhanced method and in all 78 using the standard-dose enhanced method. Radiologist Two correctly identified appendicitis in all 78 patients using both methods.

Diagnostic confidence, visualization score for a normal appendix, and correct alternative diagnosis tended to be compromised with use of low-dose unenhanced CT, showing a significant difference for a reader's confidence in the diagnosis of appendicitis, the authors wrote. The two techniques were comparable in the diagnosis of appendiceal perforation.

"Considering the high incidence of appendicitis in the general population and the rapidly increasing use of CT, small individual risks applied to such an increasingly large population may create a public health issue in the future," said the study's co-author Kyoung Ho Lee, MD.

"Low-dose unenhanced CT can potentially be used as the first line imaging test in patients suspected of having appendicitis," he added.