title: Obesometric factors associated with increased skin-to-stone distances in renal stone patients.
abstract: BACKGROUND
  Obese patients are at increased risk for renal stones as well as treatment failures due to increased skin-to-stone distances (SSD) and harder stone compositions.  We investigated the relationships between obesometric parameters (body mass index [BMI], body fat distribution and obesity-related hormone levels) with SSD and stone hardness.
  
  
  METHODS
  We prospectively enrolled patients undergoing stone interventions at our institution.  Computed tomography (CT) scans were analyzed; adipose tissue was identified according to Hounsfield units (HU) and separated into subcutaneous (SAT) and visceral (VAT) components.  The pixels were averaged at three levels to calculate fat distribution: %VAT = (VAT)/(VAT + SAT).  SSD was measured and HU were used as a surrogate for stone hardness.  Obesity-related hormones leptin and adiponectin were measured by ELISA.
  
  
  RESULTS
  Seventy-nine patients were prospectively enrolled.  Mean BMI and %VAT were 30.02 kg/m2 and 40.13 kg/m2.  Mean leptin and adiponectin levels were 17.5 ng/mL and 7.67 mcg/mL indicating high risk for metabolic consequences of obesity.  Females had greater proportions of subcutaneous fat than males (%VAT 28.4 versus 46.94, p < 0.001) and greater SSD (11.26 cm versus 9.86 cm, p = 0.025).  Among obese patients, subcutaneous fat correlated with SSD independently of BMI (r = 0.454, p = 0.008).  Obese patients with %VAT > 40 versus < 40 had SSD of 11.35 cm versus 13.7 cm (p = 0.005).  Diabetics had harder stone compositions as measured by HU than non-diabetics (982.86 versus 648.86, p = 0.001).
  
  
  CONCLUSIONS
  Obesometric parameters such as BMI, body fat distribution, and the presence of diabetes mellitus are important considerations in the management of renal stone disease.  A large proportion of subcutaneous fat, which can be estimated by physical examination, predicts SSD among obese patients and may aid treatment decisions in patients, particularly those without pre-treatment CT scans.  Further studies are needed to refine the role of obesometrics in personalizing treatment decisions.
authors.affiliation: Department of Urology, St. Joseph's Healthcare, Hamilton, Ontario, Canada.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Allard
authors.forename: Anatoly
authors.initials: A
authors.lastname: Shuster
authors.forename: Jehonathan H
authors.initials: JH
authors.lastname: Pinthus
authors.forename: Forough
authors.initials: F
authors.lastname: Farrokhyar
authors.forename: A
authors.initials: A
authors.lastname: Raees
authors.forename: Michael
authors.initials: M
authors.lastname: Patlas
authors.forename: Edward D
authors.initials: ED
authors.lastname: Matsumoto
authors.forename: J Paul
authors.initials: JP
authors.lastname: Whelan
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D050218:Body Fat Distribution; D015992:Body Mass Index; D002170:Canada / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D050152:Intra-Abdominal Fat; D007669:Kidney Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology*; D011379:Prognosis; D011446:Prospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D050151:Subcutaneous Fat; D014057:Tomography, X-Ray Computed / Q000379:methods; D014894:Weights and Measures; D055815:Young Adult