title: Intra-Appendiceal Air at CT: Is It a Useful or a Confusing Sign for the Diagnosis of Acute Appendicitis?
abstract: OBJECTIVE
  To investigate the significance of intra-appendiceal air at CT for the evaluation of appendicitis.
  
  
  METHODS
  We retrospectively analyzed 458 patients (216 men, 242 women; age range, 18-91 years) who underwent CT for suspected appendicitis. Two independent readers reviewed the CT. Prevalence, amount, and appearance of intra-appendiceal air were assessed and compared between the patients with and without appendicitis. Performance of CT diagnosis was evaluated in two reading strategies: once ignoring appendiceal air (strategy 1), and the other time considering presence of appendiceal air as indicative of no appendicitis in otherwise indeterminate cases (strategy 2), using receiver operating characteristic (ROC) analysis.
  
  
  RESULTS
  Of the 458 patients, 102 had confirmed appendicitis. The prevalence of intra-appendiceal air was significantly different between patients with (13.2%) and without (79.8%) appendicitis (p < 0.001). The amount of appendiceal air was significantly lesser in patients having appendicitis as compared with the normal group, for both reader 1 (p = 0.011) and reader 2 (p = 0.002). Stool-like appearance and air-fluid levels were more common in the appendicitis group than in the normal appendix for both readers (p < 0.05). Areas under the ROC curves were not significantly different between strategies 1 and 2 in reader 1 (0.971 vs. 0.985, respectively; p = 0.056), but showed a small difference in reader 2 (0.969 vs. 0.986, respectively; p = 0.042).
  
  
  CONCLUSIONS
  Although significant differences were seen in the prevalence, amount, and appearance of intra-appendiceal air between patients with and without appendicitis, it has a limited incremental value for the diagnosis of acute appendicitis.
authors.affiliation: Department of Radiology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Hye-Suk
authors.initials: HS
authors.lastname: Hong
authors.affiliation: Department of Radiology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Hyun Suk
authors.initials: HS
authors.lastname: Cho
authors.affiliation: Department of Radiology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Woo
authors.affiliation: Department of Radiology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Yul
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Radiology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Ik
authors.initials: I
authors.lastname: Yang
authors.affiliation: Department of Radiology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Hwang
authors.affiliation: Department of Radiology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Han Myun
authors.initials: HM
authors.lastname: Kim
authors.affiliation: Department of Pathology, Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul 07441, Korea.
authors.forename: Jeong Won
authors.initials: JW
authors.lastname: Kim
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001064:Appendicitis / Q000000981:diagnostic imaging* / Q000473:pathology; D001065:Appendix / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012372:ROC Curve; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Acute appendicitis; CT diagnosis; Intra-appendiceal air