Open Access

ARTICLE

Obesometric factors associated with increased skin-to-stone distances in renal stone patients

Christopher B. Allard¹, Anatoly Shuster², Jehonathan H. Pinthus³, Forough Farrokhyar⁴, A. Raees¹, Michael Patlas², Edward D. Matsumoto¹, J. Paul Whelan¹

1 Department of Urology, St. Joseph’s Healthcare, Hamilton, Ontario, Canada
2 Department of Radiology, Hamilton Health Sciences, Hamilton, Ontario, Canada
3 Department of Urology, Hamilton Health Sciences, Hamilton, Ontario, Canada
4 Department of Surgery, St. Joseph’s Healthcare, Hamilton, Ontario, Canada
Address correspondence to Dr. Paul Whelan, Departments of Urology, St Joseph’s Healthcare, 50 Charlton Avenue East, Hamilton, Ontario L8N 4A6 Canada

Canadian Journal of Urology 2012, 19(6), 6554-6559.

Abstract

Introduction: 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.
Materials and 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).
Conclusion: 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.

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