title: MR imaging of the normal appendix and acute appendicitis.
abstract: OBJECTIVE
  To describe the MR appearance of the normal appendix and the MR imaging characteristics of acute appendicitis with correlation to pathological severity.
  
  
  METHODS
  A total of 20 volunteers participated in this study to demonstrate normal appendices by MR imaging. A total of 37 consecutive patients with clinically diagnosed acute appendicitis were also scanned. T1-weighted (T1WI) spin-echo images, T2-weighted (T2WI) fast spin-echo, and fat-suppressed spectral presaturation inversion recovery T2-weighted (T2SPIR) fast spin-echo images were obtained. The MR criteria for considering acute appendicitis were as follows: 1) thickening of the appendiceal wall with high intensity on T2WI or T2SPIR; 2) dilated lumen filled with high intensity material on T2WI or T2SPIR; and 3) increased intensity of periappendiceal tissue on T2WI or T2SPIR.
  
  
  RESULTS
  The visibility of a normal appendix on MR imaging was 90% (18/20). It appeared as a cord-like structure of medium intensity without fluid collection in the lumen. A total of 30 cases with clinically diagnosed acute appendicitis had positive MR findings and all except one were pathologically proven. The one had cecal diverticulitis. These cases demonstrated filled lumen, with a hypointense wall on T1WI and slightly hyperintense on T2WI or T2SPIR. MR findings correlated well with pathological severity, especially a thicker wall, periappendiceal high intensity, and ascites were useful for suspecting severe appendicitis.
  
  
  CONCLUSIONS
  Correct diagnosis of acute appendicitis was obtained with MRI, and correlated well with its pathological severity. MRI is a powerful alternative for diagnosing acute appendicitis especially for the patients in whom the radiation is major concern.
authors.affiliation: Department of Radiology, Shiga University of Medical Science, Otsu, Shiga, Japan. r34nitta@belle.shiga-med.ac.jp
authors.forename: Norihisa
authors.initials: N
authors.lastname: Nitta
authors.forename: Masashi
authors.initials: M
authors.lastname: Takahashi
authors.forename: Akira
authors.initials: A
authors.lastname: Furukawa
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Murata
authors.forename: Masayuki
authors.initials: M
authors.lastname: Mori
authors.forename: Masanobu
authors.initials: M
authors.lastname: Fukushima
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D001064:Appendicitis / Q000175:diagnosis* / Q000473:pathology; D001065:Appendix / Q000033:anatomy & histology*; D001201:Ascites / Q000175:diagnosis; D002429:Cecal Diseases / Q000175:diagnosis; D002481:Cellulitis / Q000473:pathology; D004108:Dilatation, Pathologic / Q000175:diagnosis / Q000473:pathology; D004238:Diverticulitis / Q000175:diagnosis; D005260:Female; D005734:Gangrene / Q000473:pathology; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged