title: Prospective study on ultrasonography plus plain radiography in predicting residual obstruction after extracorporeal shock wave lithotripsy for ureteral stones.
abstract: OBJECTIVE
  To compare ultrasonography (US) and plain radiography with intravenous urography (IVU) in predicting ureteral obstruction after in situ extracorporeal shock wave lithotripsy (ESWL) for ureteral stones.
  
  
  METHODS
  From April 1998 to September 2000, 100 consecutive patients with solitary ureteral stones were treated by primary in situ ESWL. ESWL failures were salvaged by ureteroscopic lithotripsy. Ninety-three patients completed the follow-up assessment. US and IVU were performed when plain radiography showed no residual stone. The occurrence of hydronephrosis on US was compared with IVU, the reference standard for ureteral obstruction.
  
  
  RESULTS
  Of the 93 patients, 72 were men and 21 women (mean age 52 years; mean stone size 11.2 mm). ESWL successfully treated 70 ureteral stones (75%), and the 23 failures were treated by ureteroscopic lithotripsy. Sixty-nine patients without hydronephrosis on US had no ureteral obstruction on IVU. Of the 24 patients who had hydronephrosis on US, 8 had ureteral obstruction on IVU. Of the 85 patients who had no ureteral obstruction on IVU, 69 patients showed no evidence of hydronephrosis on US. However, all patients with ureteral obstruction on IVU demonstrated hydronephrosis on US. The sensitivity, specificity, and positive and negative predictive value concerning sonographic hydronephrosis in the prediction of ureteral obstruction was 100%, 81%, 33%, and 100%, respectively. US alone could not define the cause of ureteral obstruction.
  
  
  CONCLUSIONS
  Plain abdominal radiography plus US is highly sensitive for screening ureteral obstruction after primary in situ ESWL for ureteral calculi. It can save up to 74% of patients from the potential risk of IVU. The detection of the cause of obstruction by IVU is only necessary when sonographic evidence of hydronephrosis is present.
authors.affiliation: Division of Urology, Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, People's Republic of, Hong Kong, China.
authors.forename: M C
authors.initials: MC
authors.lastname: Cheung
authors.forename: Y L
authors.initials: YL
authors.lastname: Leung
authors.forename: B B W
authors.initials: BB
authors.lastname: Wong
authors.forename: S M
authors.initials: SM
authors.lastname: Chu
authors.forename: F
authors.initials: F
authors.lastname: Lee
authors.forename: P C
authors.initials: PC
authors.lastname: Tam
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging / Q000209:etiology; D008096:Lithotripsy / Q000379:methods; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016879:Salvage Therapy; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D014514:Ureteral Calculi / Q000150:complications / Q000175:diagnosis* / Q000628:therapy*; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging* / Q000209:etiology; D018666:Ureteroscopy; D014567:Urography / Q000379:methods*