title: Unenhanced helical CT criteria to differentiate distal ureteral calculi from pelvic phleboliths.
abstract: OBJECTIVE
  To identify imaging features at unenhanced helical computed tomography (CT) that help differentiate distal ureteral calculi from pelvic phleboliths.
  
  
  METHODS
  Retrospective analysis was performed of 184 pelvic calcifications identified at unenhanced helical CT in 113 patients. The size, shape, and attenuation of each calcification were recorded in addition to the presence of a central lucency and the appearance of the adjacent soft tissues. With profile analysis, a graphic representation was generated of attenuation in each pixel along a line drawn through each calcification.
  
  
  RESULTS
  Geometric configuration was seen in eight (21%) calculi but not in any phleboliths. Differences were significant (P < .0001) between the mean attenuation of calculi and that of phleboliths. Among phleboliths, none had a mean attenuation greater than 278 HU, 13 (9%) had a visible central lucency, 31 (21%) had a bifid peak at profile analysis, 30 (21%) had the "comet sign" (adjacent eccentric, tapering soft-tissue mass corresponding to the noncalcified portion of a pelvic vein), and three (2%) had the soft-tissue rim sign (edema of the ureteral wall). Among calculi, none had a central lucency, bifid peak, or comet sign, but 29 (76%) had the soft-tissue rim sign.
  
  
  CONCLUSIONS
  Analysis of pelvic calcifications at unenhanced helical CT can help differentiate calculi from phleboliths.
authors.affiliation: Department of Radiology, Boston University School of Medicine, Boston Medical Center, MA 02118, USA.
authors.forename: T V
authors.initials: TV
authors.lastname: Bell
authors.forename: H M
authors.initials: HM
authors.lastname: Fenlon
authors.forename: B D
authors.initials: BD
authors.lastname: Davison
authors.forename: H K
authors.initials: HK
authors.lastname: Ahari
authors.forename: S
authors.initials: S
authors.lastname: Hussain
mesh_terms: D002137:Calculi / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D004487:Edema / Q000000981:diagnostic imaging; D005544:Forecasting; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D010388:Pelvis / Q000098:blood supply*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014514:Ureteral Calculi / Q000000981:diagnostic imaging*; D014515:Ureteral Diseases / Q000000981:diagnostic imaging; D014652:Vascular Diseases / Q000000981:diagnostic imaging; D014680:Veins