title: Preoperative stone attenuation value predicts success after shock wave lithotripsy in children.
abstract: OBJECTIVE
  We determined whether stone attenuation can predict stone fragmentation after shock wave lithotripsy in the pediatric population. Previous studies show that preoperative attenuation in HU on noncontrast computerized tomography predicts shock wave lithotripsy success. To our knowledge study of this parameter in the pediatric population has been lacking to date.
  
  
  METHODS
  We performed a multi-institutional review of the records of 53 pediatric patients 1 to 18 years old who underwent shock wave lithotripsy for 3.8 to 36.0 mm renal calculi. Stone size, average skin-to-stone distance and attenuation value were determined by bone windows on preoperative noncontrast computerized tomography. Success was defined as radiographically stone-free status at 2 to 12-week followup after a single lithotripsy session without the need for further sessions or ancillary procedures.
  
  
  RESULTS
  After lithotripsy 33 patients (62%) were stone-free and 20 had incomplete fragmentation or required additional procedures. Mean ± SD stone attenuation in successfully treated patients vs those with incomplete fragmentation was 710 ± 294 vs 994 ± 379 HU (p = 0.007). Logistical regression analysis revealed that only attenuation in HU was a significant predictor of success. When patients were stratified into 2 groups (less than 1,000 and 1,000 HU or greater), the shock wave lithotripsy success rate was 77% and 33%, respectively (p <0.003).
  
  
  CONCLUSIONS
  Stone attenuation less than 1,000 HU is a significant predictor of shock wave lithotripsy success in the pediatric population. This finding suggests that attenuation values have a similar predictive value in the pediatric population as that previously reported in the adult population.
authors: Department of Urologic Surgery, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota, USA.
authors: Sean
authors: S
authors: McAdams
authors: Nicholas
authors: N
authors: Kim
authors: Daniel
authors: D
authors: Dajusta
authors: Manoj
authors: M
authors: Monga
authors: Indupur R
authors: IR
authors: Ravish
authors: Rajendra
authors: R
authors: Nerli
authors: Linda
authors: L
authors: Baker
authors: Aseem R
authors: AR
authors: Shukla
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007669:Kidney Calculi / Q000000981:diagnostic imaging / Q000628:therapy*; D008096:Lithotripsy; D008297:Male; D011300:Preoperative Care; D011379:Prognosis; D012074:Remission Induction; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014514:Ureteral Calculi / Q000000981:diagnostic imaging / Q000628:therapy*