title: Fluid-fluid levels in ovarian teratomas.
abstract: BACKGROUND
  We evaluated the imaging features of ovarian teratomas containing fluid-fluid levels on ultrasonography (US).
  
  
  METHODS
  We retrospectively reviewed US examinations of two groups with 805 masses (370 benign ovarian teratomas and 435 nonteratomatous adnexal masses).
  
  
  RESULTS
  In 27 teratomas and eight nonteratomatous adnexal masses, fluid-fluid levels were detected on US. According to the echogenicity of each layer, 27 teratomas were classified as three types: 1, supernatant hypoechoic and dependent hyperechoic layers (n = 16); 2, supernatant hyperechoic and dependent hypoechoic layers (n = 8); and 3, supernatant hypoechoic and dependent hypoechoic layers with bright fluid interface (n = 3). In eight (30%) of 27 teratomas, US showed floating nodules at the interface, five of which had posterior acoustic shadowing. All eight nonteratomatous adnexal masses showed type 1 fluid-fluid levels.
  
  
  CONCLUSIONS
  The fluid-fluid level seen on US is strongly suggestive but not pathognomonic of dermoids. Fluid-fluid levels with supernatant hyperechoic and dependent hypoechoic layers, supernatant hypoechoic and dependent hypoechoic layers with bright interface, and a floating nodule might pathognomonic findings of benign ovarian teratomas.
authors.affiliation: Department of Radiology, Clinical Research Institute, Seoul National University Hospital, 28 Yongon-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: H-C
authors.initials: HC
authors.lastname: Kim
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: H J
authors.initials: HJ
authors.lastname: Lee
authors.forename: S J
authors.initials: SJ
authors.lastname: Shin
authors.forename: S-I
authors.initials: SI
authors.lastname: Hwang
authors.forename: Y H
authors.initials: YH
authors.lastname: Choi
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D013724:Teratoma / Q000175:diagnosis / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography