CT is only helpful in determining appendicitis if clinically likely
CT scans can be withheld in patients in whom emergency clinicians rate the likelihood of appendicitis as unlikely, but CT is often beneficial when appendicitis is judged to be very likely, according to a study in the October issue of the American Journal of Roentgenology.

Robert O. Nathan, MD, from the department of radiology at the University of Washington in Seattle, and colleagues prospectively evaluated the therapeutic impact of CT of the appendix in a community hospital.

For each of 100 consecutive adult patients, who presented to a community hospital emergency department from August 2006 to November 2006 and underwent CT of the appendix, the proposed treatment plan and the likelihood of appendicitis before CT were compared with the actual treatment after CT. The primary outcome assessed was change in patient management after CT. The investigators examined the percentage likelihood of appendicitis, whether patient disposition changed after CT and the presence or absence of appendicitis. They also calculated the accuracy of CT.

The investigators found that the treatment plans of the emergency clinicians changed in 29 patients. Appendicitis was ruled out on the basis of CT findings in 50 percent of patients when appendicitis was considered probable and in 60 percent when appendicitis was considered very likely.

When appendicitis was considered unlikely, the authors wrote that appendicitis was ruled out by CT in 100 percent of patients. CT of the appendix was shown to have 94 percent sensitivity, 100 percent specificity, 100 percent positive predictive value, 99 percent negative predictive value and 99 percent accuracy.

Nathan and colleagues concluded that CT may not be appropriate when some clinical indications of appendicitis are absent.

“The data suggest that CT should be performed in patients in whom emergency clinicians consider appendicitis to be probable or very likely. It could be withheld in patients in whom emergency clinicians rate appendicitis as unlikely,” according to the authors.