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Multidetector CT highly accurate for diagnosing appendicitis and ruling it out

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – When acute appendicitis is suspected, preoperative assessment by multidetector computed tomography (MDCT) has very high positive and negative predictive values, according to the results of a retrospective study reported in the June 21st issue of the Annals of Internal Medicine.

The findings “support routine use of preoperative MDCT as the standard of care for suspected appendicitis in adults,” conclude Dr. Perry J. Pickhardt and colleagues at the University of Wisconsin School of Medicine and Public Health in Madison.

The team notes that MDCT is used these days in 90% or more of cases of suspected appendicitis. While numerous studies have documented that MDCT has reduced the number of negative findings at appendectomy, there’s little information about its accuracy in ruling out appendicitis. Also, there have been relatively few studies in adults.

The investigators therefore evaluated the diagnostic performance of MDCT in 2871 adults seen at their center with suspected appendicitis. Based on MDCT evaluation, 708 of the patients went on to appendectomy, which confirmed the diagnosis of appendicitis in 665 of them. The other 2163 patients in which MDCT ruled out appendicitis were followed, and 10 of them were later diagnosed with appendicitis.

Based on these numbers, the sensitivity of MDCT in detecting appendicitis works out to be 98.5% (ie, 665 of 675 patients) and its specificity 98.0% (2153 of 2196 patients).

The positive and negative predictive values were 93.9% (605 of 708 patients) and 99.5% (2153 of 2163 patients), respectively.

In 2122 patients who did not have appendicitis or undergo appendectomy, MDCT was able to suggest another probably diagnosis in 893 cases – usually GI, gynecologic or genitourinary conditions, according to the report.

Furthermore, the researchers found, the perforation rate decreased over the course of the study period from 28.9% to 11.5%, suggesting that the increasing use of MDCT aided earlier detection of appendicitis.

“In summary,” Dr. Pickhardt and colleagues comment, “standard nonfocused MDCT of the abdomen and pelvis is a highly sensitive and specific test in the setting of suspected acute appendicitis in both men and women.”

They conclude, “Preoperative MDCT generally allows for efficient and confident inclusion or exclusion of appendicitis, resulting in reduced rates of perforation and negative findings at appendectomy, as well as providing an alternative explanation in many cases without appendicitis.”

Ann Intern Med 2011;154:789-796.