SPP1 and urolithiasis: Shape of funnel plots and results of Egger’s test (as depicted in Fig. 2, and Additional files 7 and 8) rendered calculation of the publication bias where absence of any significant publication bias was evident except for the analysis of SPP1 rs11439060 polymorphism and urolithiasis (Additional file 8, parts c and d); however, the Egger’s test was not significant (p = 0.19 for dominant model and p = 0.15 for recessive model) in that case too.