title: Differentiating xanthogranulomatous cholecystitis from wall-thickening type of gallbladder cancer: added value of diffusion-weighted MRI.
abstract: OBJECTIVE
  To evaluate the benefit of diffusion-weighted imaging (DWI) in differentiating xanthogranulomatous cholecystitis from the wall-thickening type of gallbladder cancer.
  
  
  METHODS
  This retrospective study was approved by the institutional review board. Fourteen patients with xanthogranulomatous cholecystitis and 19 patients with the wall-thickening type of gallbladder cancer were included. Qualitative (visual diffusion restriction compared to liver parenchyma) and quantitative [apparent diffusion coefficient (ADC)] analyses were performed. Conventional MRI findings including dynamic enhancement pattern between the two groups were also analysed. Two observers independently reviewed conventional magnetic resonance imaging (MRI) images and subsequently reviewed combined conventional MRI and DWI images. Pairwise comparison of the receiver operating characteristic (ROC) curves was used to compare diagnostic performances.
  
  
  RESULTS
  In conventional MRI findings, xanthogranulomatous cholecystitis showed significant continuity of enhancing mucosal line [79% (11/14) versus 26% (5/19), p = 0.003] and intramural T2-high signal intensity [64% (9/14) versus 21% (4/19), p = 0.012] compared to the wall-thickening type of gallbladder cancer. The enhancement pattern of gallbladder cancer compared to liver parenchyma showed earlier onset than that of xanthogranulomatous cholecystitis (p = 0.001). Diffusion restriction was more frequently seen in the wall-thickening type of gallbladder cancer (68%, 13/19) than in xanthogranulomatous cholecystitis (7%, 1/14; p < 0.001). The mean ADC value of xanthogranulomatous cholecystitis was higher than that of the wall-thickening type of gallbladder cancer with statistical significance (1.637 × 10(-3) mm(2)/s versus 1.076 × 10(-3) mm(2)/s, p = 0.005). Diagnostic performance [area under ROC curve (Az)] of both observers improved significantly after additional review of DWI; Az improved from 0.737 to 0.930 (p = 0.027) for observer 1 and from 0.675 to 0.938 (p = 0.008) for observer 2.
  
  
  CONCLUSIONS
  Addition of DWI to conventional MRI improves discrimination between xanthogranulomatous cholecystitis and the wall-thickening type of gallbladder cancer.
authors.affiliation: Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Gangnam-gu, Seoul, Republic of Korea.
authors.forename: T W
authors.initials: TW
authors.lastname: Kang
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: H J
authors.initials: HJ
authors.lastname: Park
authors.forename: S
authors.initials: S
authors.lastname: Lim
authors.forename: K M
authors.initials: KM
authors.lastname: Jang
authors.forename: D
authors.initials: D
authors.lastname: Choi
authors.forename: S J
authors.initials: SJ
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002764:Cholecystitis / Q000175:diagnosis* / Q000473:pathology; D003287:Contrast Media; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D005706:Gallbladder Neoplasms / Q000175:diagnosis* / Q000473:pathology; D006099:Granuloma / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D014973:Xanthomatosis / Q000175:diagnosis* / Q000473:pathology
chemical_list: D003287:Contrast Media; C073590:gadolinium ethoxybenzyl DTPA; D019786:Gadolinium DTPA