title: Outcomes and Safety of Retrograde Intra-Renal Surgery for Renal Stones Less Than 2 cm in Size.
abstract: BACKGROUND
  Retrograde intra-renal surgery (RIRS) has been used to remove stones of less than 2 cm in the kidney. However, its role is not well defined.
  
  
  OBJECTIVE
  The objective of this study was to evaluate the outcomes and safety of RIRS, used either as a primary or secondary procedure, and to analyze factors predicting the stonefree rate (SFR).
  
  
  METHODS
  A retrospective analysis was performed on data from patients who underwent RIRS over a 10-year period (2002-2012). Stone size was measured as the surface area and was calculated according to the EAU guidelines. In cases of multiple stones, the total stone burden was calculated as the sum of each stone size. Stone burden was then classified as ≤ 80 mm(2) or > 80 mm(2). RIRS was classified as primary procedure or secondary procedure (after failed extracorporeal shockwave lithotripsy or percutaneous nephrolithotripsy).Stone clearance was defined as a complete absence of stones or stones < 4 mm, which were deemed insignificant on ultrasonography and plain radiography.
  
  
  RESULTS
  The overall SFR for renal stones treated with RIRS in our center was 55.4%, and the complication rate was 1.5%, which consisted of one case of sepsis. The only factor affecting SFR in this study was the indication for RIRS. When performed as a primary operation, RIRS showed a significantly better SFR (64.3%). The SFR for lower pole stones was only 44.4%. There were no statistically significant effects of stone burden, radio-opacity, or combination with ureteral stones on SFR.
  
  
  CONCLUSIONS
  RIRS should be used as the primary treatment for renal stones whenever possible.
authors.affiliation: Urology Unit, Department of Surgery, University Kebangsaan Malaysia Medical Centre, Kuala lumpur, Malaysia.
authors.forename: Christopher C K
authors.initials: CC
authors.lastname: Ho
authors.forename: Tan Guan
authors.initials: TG
authors.lastname: Hee
authors.forename: Goh Eng
authors.initials: GE
authors.lastname: Hong
authors.forename: Praveen
authors.initials: P
authors.lastname: Singam
authors.forename: Badrulhisham
authors.initials: B
authors.lastname: Bahadzor
authors.forename: Zulkifli
authors.initials: Z
authors.lastname: Md Zainuddin
keywords: Calculi; Kidney; Ureteroscopy