Effects of Visceral Fat Area and Other Metabolic Parameters on Stone Composition in Patients Undergoing Percutaneous Nephrolithotomy

Purpose: Obesity is a risk factor for metabolic syndrome and urolithiasis, particularly uric acid stones. As estimated by visceral fat area, visceral obesity is a more specific measure of the risk of metabolic syndrome than body mass index. We investigated the effects of visceral fat area and other metabolic factors on uric acid stone formation in patients treated with percutaneous nephrolithotomy. Materials and Methods: We retrospectively reviewed the records of 269 patients who underwent percutaneous nephrolithotomy. Visceral fat area was measured in each patient on a CT axial slice at the umbilical level using the Aquarius (R) iNtuition (TM) fat analysis tool. Analysis was performed to determine the effect of visceral fat area and other comorbidities on uric acid stone formation. Results: Of the 269 patients analyzed there was no difference in baseline comorbidities between uric acid and nonuric acid stone formers. Patients with uric acid stones had a significantly higher mean visceral fat area (209.3 vs 161.9 cm(2), p = 0.001), and rates of hypertension (67.4% vs 47.3%) and coronary artery disease (14.3% vs 4.6%, each p = 0.011). On logistic regression analysis hypertension (OR 2.16, 95% CI 1.05-4.45, p = 0.04) and a high visceral fat area (OR 3.64, 95% CI 1.22-10.85, p = 0.02) were independent risk factors for uric acid stones. Conclusions: As a marker of visceral obesity, visceral fat area contributes to the risk of metabolic syndrome and urolithiasis. Uric acid stone formers showed a significantly higher hypertension rate and mean visceral fat area, which were independent risk factors for uric acid urolithiasis. Evaluating these characteristics in stone formers may facilitate a tailored metabolic assessment and treatment plan.