The impact of body mass index on the stone composition of 191 patients who received percutaneous nephrolithotomy in a single hospital

Abstract

Objective: We aimed to analyze the renal stone composition and evaluate the epidemiology of body mass index (BMI) and renal stones. Materials and Methods: We conducted a retrospective, single-center study of patients with large stones (ɮ cm) who underwent percutaneous nephrolithotomy for renal stones between 2010 and 2015. We performed stone analysis using stereomicroscopy and infrared spectroscopy to determine the chemical composition of these stones. Chi-square analysis was used to determine the relationship between BMI and renal stone formation. Results: We examined stones from 191 procedures. Among these stones, we classified 58.6% as having “pure” composition and 40.8% as having “mixed” composition. Most stones (68.1%) were composed of calcium oxalate monohydrate (COM), followed by carbonate apatite (50.8%), calcium oxalate dihydrate (COD) (36.6%), uric acid (14.1%), struvite (8.9%), ammonium hydrogen urate (2.1%), and brushite (1.0%). Chi-square analysis revealed that stones in obese patients (BMI >27 kg/m2) were more likely to contain COM (hazards ratio [HR]: 1.66, 95% confidence interval [CI]: 1.10–2.49, P = 0.008) and less COD (HR: 0.77, 95% CI: 0.60–0.99, P = 0.049) than stones in nonobese patients (BMI ≦27 kg/m2). Conclusion: COM is the most frequently occurring compound in renal stones. Obese patients were significantly more likely to develop COM-containing renal stones. One must consider these factors when choosing a treatment modality.

Keywords

• Percutaneous nephrolithotomy
• renal stones
• stone analysis