title: Appendiceal and peri-appendiceal air at CT: prevalence, appearance and clinical significance.
abstract: OBJECTIVE
  Appendiceal air has been reported as both a sign of appendicitis and of a normal appendix both at plain radiography and computed tomography (CT). It is the aim of this investigation to determine the prevalence, range of appearances, and significance of appendiceal and peri-appendiceal air at CT.
  
  
  METHODS
  Appendiceal CT scans of 100 patients with proven appendicitis and 100 patients with a normal appendix were reviewed for the presence of appendiceal and peri-appendiceal air. All cases were correlated with surgical and pathological findings or clinical follow-up.
  
  
  RESULTS
  In 100 CT cases of appendicitis, appendiceal and/or peri-appendiceal air was present in one or more forms in 31% of cases. When present, it appeared as intraluminal air bubbles (38.7%) or air-fluid levels (22.6%), appendolith air (41.9%), intramural air (16.1%), peri-appendiceal air bubbles (12.9%), or extraluminal air-fluid level(s) (29.0%). Intramural and extraluminal air correlated with perforation in 60% and 100%, respectively. In 100 CT cases of a normal appendix, air was present in 57%. It was always intraluminal and appeared as small bubbles of air (52.6%), a tubular-shaped air collection (43.9%), or as an air-fluid level (3.5%). The appendiceal lumen was either airless (43%), or minimally (32%), moderately (18%), or completely filled with air (7%).
  
  
  CONCLUSIONS
  Air is a common finding at appendiceal CT in both the normal and inflamed appendix. Intraluminal air is seen in both appendicitis and normal appendices, and cannot be presumed to indicate a patent lumen and thus a normal appendix. Appendolith, intramural and peri-appendiceal air appear diagnostic of appendicitis.
authors.affiliation: Department of Radiology, Massachusetts General Hospital, Boston 02114, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: Rao
authors.forename: J T
authors.initials: JT
authors.lastname: Rhea
authors.forename: R A
authors.initials: RA
authors.lastname: Novelline
mesh_terms: D000038:Abscess / Q000000981:diagnostic imaging; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000388:Air; D001064:Appendicitis / Q000000981:diagnostic imaging*; D001065:Appendix / Q000000981:diagnostic imaging*; D002429:Cecal Diseases / Q000000981:diagnostic imaging; D002648:Child; D002675:Child, Preschool; D004646:Emphysema / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007416:Intestinal Perforation / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D012422:Rupture, Spontaneous; D014057:Tomography, X-Ray Computed