SPP1 and urolithiasis: Currently, there is only one meta-analysis available on the subject which revealed positive association of SPP1 coding region genetic variant (rs1126616:C > T) and lower serum and urine osteopontin levels with increased risk of developing urolithiasis [40], however, they did not include any other SPP1 polymorphism (including SPP1 promoter polymorphisms investigated in this study) in the analysis, which limits the usefulness and broader applicability of that study.