title: Plain abdominal x-ray versus computerized tomography screening: sensitivity for stone localization after nonenhanced spiral computerized tomography.
abstract: OBJECTIVE
  Urolithiasis followup with plain abdominal x-ray requires adequate visualization of the calculus on the initial x-ray or computerized tomography (CT) study. We compared the sensitivity of plain abdominal x-ray versus CT for stone localization after positive nonenhanced spiral CT.
  
  
  METHODS
  We evaluated 46 consecutive nonenhanced spiral CT studies positive for upper urinary tract lithiasis for which concurrent plain abdominal x-rays were available. X-ray and CT studies were compared for the ability to visualize retrospectively a stone given its location by CT. A consensus of 1 radiologist and 3 urologists was reached in each case. Cross-sectional stone size and maximum length were measured on plain abdominal x-ray.
  
  
  RESULTS
  Plain abdominal x-ray and scout CT had 48% (22 of 46 cases) and 17% (8 of 46) sensitivity, respectively, for detecting the index stone (p <0.00004). Of the 39 stones overall visualized on plain abdominal x-ray only 19 (49%) were visualized on scout CT. Mean cross-sectional area and length of the stones on scout CT were 0.34 cm.2 (approximately 6 x 5.5 mm.) and 6. 5 mm., respectively, while the average size of those missed was 0.11 cm.2 (approximately 4 x 3 mm.) and 3.6 mm. The mean size differences in the groups were highly significant (p <0.0009).
  
  
  CONCLUSIONS
  Plain abdominal x-ray is more sensitive than scout CT for detecting radiopaque nephrolithiasis. Of the stones visible on plain abdominal x-ray 51% were not seen on CT. To facilitate outpatient clinic followup of patients with calculi plain abdominal x-ray should be performed when a stone is not clearly visible on scout CT.
authors.affiliation: James Buchanan Brady Urological Institute and Department of Radiology, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
authors.forename: S V
authors.initials: SV
authors.lastname: Jackman
authors.forename: S R
authors.initials: SR
authors.lastname: Potter
authors.forename: F
authors.initials: F
authors.lastname: Regan
authors.forename: T W
authors.initials: TW
authors.lastname: Jarrett
mesh_terms: D006801:Humans; D007669:Kidney Calculi / Q000000981:diagnostic imaging; D011860:Radiography, Abdominal / Q000379:methods*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014514:Ureteral Calculi / Q000000981:diagnostic imaging; D014545:Urinary Calculi / Q000000981:diagnostic imaging*