title: Comparison of urinary stone and stent encrustation: biochemical analysis.
abstract: OBJECTIVE
  To compare biochemical analysis of stent encrustation with that of urinary stones from the same patient.
  
  
  METHODS
  Any patient presenting from February to December 2000 with a symptomatic ureteral or renal calculus that necessitated stenting and delayed calculus retrieval was enrolled in the study. The stent and stone were sent to the same laboratory for qualitative and semiquantitative chemical analysis. A total of 50 stents and matched calculi were available for comparison; four stents were excluded because they had insufficient encrustation for analysis.
  
  
  RESULTS
  Two patients had open ureterolithotomy; the remainder were treated by endoscopic or percutaneous means. Every stone containing calcium oxalate had a stent that was positive for calcium oxalate. Four uric acid stones were available for comparison, and three of the four matched stents tested positive for uric acid.
  
  
  CONCLUSIONS
  Biochemical analysis of urinary stent encrustation is a good predictor of urinary stone composition, especially for calcium oxalate-containing stones. Uric acid stent encrustation is likely to occur in patients with uric acid stones.
authors.affiliation: Department of Urology, Gosford District Hospital, NSW, Australia. bariol@ozemail.com.au
authors.forename: Simon
authors.initials: S
authors.lastname: Bariol
authors.forename: Trent
authors.initials: T
authors.lastname: Farebrother
authors.forename: Stephen
authors.initials: S
authors.lastname: Ruthven
authors.forename: Finlay
authors.initials: F
authors.lastname: MacNeil
mesh_terms: D002129:Calcium Oxalate / Q000032:analysis*; D006801:Humans; D011183:Postoperative Complications / Q000209:etiology; D015607:Stents; D014527:Uric Acid / Q000032:analysis*; D014545:Urinary Calculi / Q000737:chemistry*
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid