title: Clearance of lower-pole stones following shock wave lithotripsy: effect of the infundibulopelvic angle.
abstract: OBJECTIVE
  To assess the effect of anatomic factors, especially the angle of the lower-pole infundibulum, on stone clearance following shock wave lithotripsy (SWL) in order to determine selection criteria for percutaneous nephrolithotomy.
  
  
  METHODS
  We retrospectively analyzed 116 patients with single lower-pole stones measuring 11-20 mm treated with SWL. Intravenous urograms were reviewed to measure the infundibulopelvic angle, the angle of the infundibulum to the vertical, and the anatomy of lower-pole calyces.
  
  
  RESULTS
  The overall stone-free rate was 52%. Factors most closely associated with a stone-free status were obtuse infundibulopelvic angle, lack of calyceal distortion, and a large infundibular diameter. The infundibulopelvic angle was the only factor to attain significance in predicting stone-free status (p = 0.012). The size of the stone did not predict eventual stone-free status (p = 0.911), but larger stones were more likely to require intervention after SWL.
  
  
  CONCLUSIONS
  For solitary lower-pole stones 11-20 mm in size, the angle of the lower-pole infundibulum as it relates to the pelvis plays a role in eventual stone clearance and should be taken into account before choosing a mode of treatment.
authors.affiliation: Scottish Lithotriptor Centre, Western General Hospital, Edinburgh, UK.
authors.forename: F X
authors.initials: FX
authors.lastname: Keeley
authors.forename: S A
authors.initials: SA
authors.lastname: Moussa
authors.forename: G
authors.initials: G
authors.lastname: Smith
authors.forename: D A
authors.initials: DA
authors.lastname: Tolley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000175:diagnosis / Q000628:therapy*; D007682:Kidney Pelvis / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008096:Lithotripsy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D016896:Treatment Outcome; D014567:Urography