title: Utility of the Guy's stone score based on computed tomographic scan findings for predicting percutaneous nephrolithotomy outcomes.
abstract: OBJECTIVE
  To evaluate the ability of the Guy's stone score (GS) to predict the success rates and complications on the basis of the computed tomographic (CT) scan findings for renal stones treated with percutaneous nephrolithotomy (PCNL).
  
  
  METHODS
  From 2008 to 2012, a total of 147 consecutive patients (155 renal units) who underwent PCNL in a completely supine position were prospectively evaluated. All patients underwent a CT scan preoperatively, and the stones were classified according to the GS. All PCNLs were analyzed to determine the association between the GS and treatment outcomes on the basis of CT findings and complications, according to the Clavien criteria.
  
  
  RESULTS
  Of the 155 PCNLs, 27% were classified as GS1, 28.4% as GS2, 27% as GS3, and 17.6% as GS4. Only the largest diameter of the stones differed among the groups (GS1=21.4, GS2=26.5, GS3=31.4, and GS4=50.5 mm; P<.001). After stratification according to the GS, the groups differed significantly regarding their operative times (GS1=63±28.5, GS2=101.4±40.8, GS3=127.6±47.6, and GS4=153.3±56 minutes; P<.001), tubeless rates (GS1=54.8%, GS2=45.4%, GS3=28.6%, and GS4=7.4%; P<.001), blood transfusion rates (GS1=0%, GS2=2.3%, GS3=4.8%, and GS4=22.2%; P=.01), complications (GS1=4.8%, GS2=9.1%, GS3=26.2%, and GS4=44.4%; P<.001), immediate success rates (GS1=95.2%, GS2=79.5%, GS3=59.5%, and GS4=40.7%; P<.001), and number of auxiliary procedures (GS1=0.05±0.32, GS2=0.28±0.6, GS3=0.35±0.66, and GS4=0.43±0.59; P=.031). The final success rates after the auxiliary procedures were similar among the groups (GS1=97.6%, GS2=86.4%, GS3=90.5%, and GS4=74.5%; P=.19).
  
  
  CONCLUSIONS
  The GS based on CT findings accurately predicted success rates and complications after PCNL for renal stones.
authors.affiliation: Section of Endourology, Division of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil; Section of Endourology, Division of Urology, Men's Health Centre, Hospital Brigadeiro, Sao Paulo, Sao Paulo, Brazil. Electronic address: fabio@drfabiovicentini.com.br.
authors.forename: Fabio C
authors.initials: FC
authors.lastname: Vicentini
authors.affiliation: Section of Endourology, Division of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Giovanni Scala
authors.initials: GS
authors.lastname: Marchini
authors.affiliation: Section of Endourology, Division of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Mazzucchi
authors.affiliation: Section of Endourology, Division of Urology, Men's Health Centre, Hospital Brigadeiro, Sao Paulo, Sao Paulo, Brazil.
authors.forename: Joaquim F A
authors.initials: JF
authors.lastname: Claro
authors.affiliation: Section of Endourology, Division of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Miguel
authors.initials: M
authors.lastname: Srougi
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000145:classification / Q000000981:diagnostic imaging* / Q000601:surgery*; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D009403:Nephrostomy, Percutaneous / Q000009:adverse effects / Q000379:methods*; D061646:Operative Time; D011183:Postoperative Complications / Q000453:epidemiology / Q000503:physiopathology; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome