CT signs may predict image-occult appendicitis complications

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Intraluminal air in an obstructed appendix and presence of an intraluminal appendicolith in the setting of acute appendicitis provide markers of perforated or necrotic appendicitis, according to a study published in the October issue of Academic Radiology.

“Prompt diagnosis of acute appendicitis is critical, because treatment of appendicitis before perforation significantly decreases morbidity and mortality,” wrote Joseph T. Azok, MD, from the Mallinckrodt Institute of Radiology at Washington University in St. Louis, and colleagues.

CT imaging plays a valuable role, and is used in more than 90 percent of adult patients with acute appendicitis in the U.S. However, the presence of intraluminal appendiceal air has been a confusing sign. Some studies have suggested it is associated with appendicitis, while others suggest it signifies normalcy where it confirms luminal patency.

Azok and colleagues designed a retrospective analysis to determine the predictive value of intraluminal appendiceal air in the setting of acute appendicitis when necrosis or perforation was not apparent at imaging. Other potential predictive factors, including the presence of an intraluminal appendicolith, age and gender, also were investigated.

The researchers focused on 374 patients with pathologically proven appendicitis who underwent CT imaging from Jan. 1, 2006, to Dec. 31, 2008.

Four reviewers independently analyzed CT exams for the presence of perforation and resolved discordant cases by consensus. Reviewers were blinded to the operative note and pathologic report, which served as ground truth for the presence of appendiceal necrosis and perforation.

Among the main study cohort, 17.4 percent of patients showed evidence of necrosis and/or perforation at ground truth.

The reviewers reported intraluminal air within an obstructed appendix in 21.4 percent of the study group. A univariate model demonstrated the presence of intraluminal appendiceal air represented a risk factor for necrosis and/or perforation with an odds ratio of 2.64, according to Azok and colleagues.

However, its absence did not negate the possibility of occult perforation or necrosis as 13.9 percent of patients who lacked CT sign of intraluminal air were positive at ground truth. Thus, sensitivity and specificity of intraluminal air for image-occult necrosis or perforation were 36.9 percent and 81.9 percent, respectively.

Intraluminal appendicoliths were present in 35.8 percent of the study population, and determined to be a risk factor for necrosis and/or perforation, with an odds ratio of 2.67, reported Azok et al. Sensitivity and specificity were 55.4 percent and 68.3 percent, respectively.

Age also emerged as a predictive risk factor, according to the researchers.

“Our study clearly demonstrates that intraluminal air is a risk factor for perforation or necrosis complicating acute appendicitis … In this setting, the presence of intraluminal air suggests a more serious clinical scenario in which the appendicitis may indeed be complicated by image-occult perforation or necrosis,” wrote the authors.

They acknowledged the low sensitivity of both intraluminal air and appendicoliths, but emphasized that the presence of either finding predicts increased likelihood of necrosis or perforation.

“Alongside other independent predictors such as appendicoliths and increasing age, this finding [intraluminal air] should prompt clinicians to aggressively attend to these patients to avoid the higher morbidity associated with delayed treatment of complicated appendicitis,” Azok et al concluded.