title: The skin-to-calyx distance measured by renal ct scan and ultrasound.
abstract: OBJECTIVE
  We developed a stereotactic device to guide the puncture for percutaneous nephrolithotripsy, which uses the distance from the target calyx to its perpendicular point on skin (SCD) to calculate the needle´s entry angle. This study seeks to validate the use of measurements obtained by ultrasound (US) and computerized tomography (CT) for needle´s entry angle calculation and to study factors that may interfere in this procedure.
  
  
  METHODS
  Height, weight, abdominal circumference, CT of the urinary tract in dorsal decubitus (DD) and ventral decubitus (VD), and US of the kidneys in VD were obtained from thirty-five renal calculi patients. SCD obtained were compared and correlated with body-mass index (BMI).
  
  
  RESULTS
  BMI was 28.66 ± 4.6 Kg/m2. SCD on CT in DD was 8.40 ± 2.06cm, in VD was 8.32 ± 1.95cm, in US was 6.74 ± 1.68cm. SCD measured by US and CT were statistically different (p < 0.001), whereas between CT in DD and VD were not. SCD of the lower calyx presented moderate correlation with BMI.
  
  
  CONCLUSIONS
  SCD obtained by CT in ventral and dorsal decubitus may be used for calculation of the needle´s entry angle. SCD obtained by US cannot be used. A rule for the correlation between BMI and the SCD could not be determined.
authors.affiliation: Division of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Chen Jen
authors.initials: CJ
authors.lastname: Shan
authors.affiliation: Section of Endourology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Mazzucchi
authors.affiliation: Division of Radiology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Fabio
authors.initials: F
authors.lastname: Payao
authors.affiliation: Division of Radiology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Andrea Cavalanti
authors.initials: AC
authors.lastname: Gomes
authors.affiliation: Division of Radiology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Ronaldo Hueb
authors.initials: RH
authors.lastname: Baroni
authors.affiliation: Section of Endourology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Fabio Cesar
authors.initials: FC
authors.lastname: Torricelli
authors.affiliation: Section of Endourology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, Brazil.
authors.forename: Fabio Carvalho
authors.initials: FC
authors.lastname: Vicentini
authors.affiliation: Division of Urology, University of Sao Paulo Medical School, Sao Paulo, SP, Brazil.
authors.forename: Miguel
authors.initials: M
authors.lastname: Srougi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015992:Body Mass Index; D004867:Equipment Design; D005260:Female; D006801:Humans; D007670:Kidney Calices / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012867:Skin / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D013238:Stereotaxic Techniques / Q000295:instrumentation*; D016683:Supine Position; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods; D014463:Ultrasonography; D055105:Waist Circumference; D055815:Young Adult