title: The onion skin sign: a specific sonographic marker of appendiceal mucocele.
abstract: OBJECTIVE
  To evaluate the association of the onion skin sign as a sonographic marker for appendiceal mucocele.
  
  
  METHODS
  The sonographic onion skin sign was considered specific for the preoperative diagnosis of appendiceal mucocele. Therefore, detection of this sign in a mass located in the right lower abdomen, unrelated to the female reproductive organs, indicated surgical intervention with a presumptive diagnosis of appendiceal mucocele. From 1998 through 2001, female patients who were found to have atypical cysts containing this sign underwent surgery. The cases were closely followed, and intraoperative findings and final histologic diagnoses were recorded.
  
  
  RESULTS
  Appendiceal mucocele was the final diagnosis in all 7 patients in whom the onion skin sign was observed. One additional patient had an appendiceal mucocele with a sonographic picture of a clear tubular cystic structure.
  
  
  CONCLUSIONS
  A sonographically layered cystic mass in the right lower quadrant of the abdomen in the presence of a normal ovary strongly suggests the diagnosis of appendiceal mucocele. Recognition of the sonographic onion skin sign in a cystic mass in the right lower quadrant may facilitate the accurate preoperative diagnosis of appendiceal mucocele.
authors.affiliation: Ultrasound Unit, Department of Obstetrics and Gynecology, Kaplan Medical Center, Rehovot, Israel. bcaspi@inter.net.il
authors.forename: Benjamin
authors.initials: B
authors.lastname: Caspi
authors.forename: Eran
authors.initials: E
authors.lastname: Cassif
authors.forename: Roni
authors.initials: R
authors.lastname: Auslender
authors.forename: Arie
authors.initials: A
authors.lastname: Herman
authors.forename: Zion
authors.initials: Z
authors.lastname: Hagay
authors.forename: Zvi
authors.initials: Z
authors.lastname: Appelman
mesh_terms: D000328:Adult; D000368:Aged; D001065:Appendix / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009078:Mucocele / Q000000981:diagnostic imaging*; D014463:Ultrasonography