title: Detection of uric acid stones in the ureter using low- and conventional-dose computed tomography.
abstract: OBJECTIVE
  To determine the ability of low- and conventional-dose computed tomography (CT) in identification of uric acid stones, which are of lower density than calcium oxalate stones.
  
  
  METHODS
  Uric acid stones (3, 5, and 7 mm) were randomly placed in human cadaveric ureters and scanned using conventional 140-mAs and low-dose 70-, 50-, 30-, 15-, 7.5-, and 5-mAs settings. A single-blinded radiologist reviewed a total of 523 scanned stone images. Sensitivity and specificity were compared among different settings and stone sizes.
  
  
  RESULTS
  Imaging using 140-, 70-, 50-, 30-, 15-, 7.5-, and 5-mAs settings resulted in 97%, 97%, 96%, 93%, 83%, 83%, and 69% sensitivity and 92%, 92%, 91%, 89%, 88%, 91%, and 94% specificity, respectively. There was a significant difference in sensitivity between 140 mAs and 15, 7.5, and 5 mAs (P = .011, P = .011, and P <.001, respectively). Sensitivity for 3-, 5-, and 7-mm stones was 83%, 90%, and 93%, respectively. At ≤ 15 mAs, 3-mm stones had a higher rate of false negatives (P <.001).
  
  
  CONCLUSIONS
  Both low- and conventional-dose CTs demonstrate excellent sensitivity and specificity for the detection of ureteral uric acid stones. However, low-dose CT at ≤ 15 mAs resulted in reduced detection of uric acid stones.
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Gene O
authors.initials: GO
authors.lastname: Huang
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Engebretsen
authors.affiliation: Department of Radiology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Jason C
authors.initials: JC
authors.lastname: Smith
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Caroline L
authors.initials: CL
authors.lastname: Wallner
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Culpepper
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Creech
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Caleb C
authors.initials: CC
authors.lastname: Ng
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Mai
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Chung
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Gaudencio
authors.initials: G
authors.lastname: Olgin
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA.
authors.forename: Don C
authors.initials: DC
authors.lastname: Arnold
authors.affiliation: Department of Urology, Loma Linda University Medical Center, Loma Linda, CA. Electronic address: dbaldwin@llu.edu.
authors.forename: D Duane
authors.initials: DD
authors.lastname: Baldwin
mesh_terms: D002102:Cadaver; D002129:Calcium Oxalate / Q000737:chemistry; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014513:Ureter / Q000000981:diagnostic imaging; D014514:Ureteral Calculi / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D014527:Uric Acid / Q000032:analysis*
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid