Diabetes mellitus and the risk of urolithiasis: a meta-analysis of observational studies.

Diabetes mellitus (DM) might increase the risk of urolithiasis, but the results were inconsistent. Hence, we conducted a meta-analysis to assess the association between DM and the risk of urolithiasis. We searched PubMed, Embase, and Cochrane Library to identify the relevant observational studies up to November 2014. Reference lists of retrieved articles were also reviewed. Summary relative risks (RRs) and corresponding 95% confidence intervals (CIs) were used to estimate the association between DM and the risk of urolithiasis. We identified 3 case-control studies and 4 cohort studies regarding DM and the risk of urolithiasis, involving 247,531 participants. Analyses of all studies showed that DM was associated with an increased risk of urolithiasis (RR=1.24, 95% CI: 1.14-1.35). There was heterogeneity among studies (p=0.027, I2=57.9%). The association between DM and the risk of urolithiasis was not significantly differed by gender, but this association was inconsistent in the North American and Asian populations. When restricting the analysis to studies that had adjusted for body mass index (n=2) or hypertension (n=3), the RRs were 1.46 (95% CI: 1.03-2.06) and 1.22 (95% CI: 1.01-1.48), respectively. There was no significant publication bias (p=0.96 for Egger's regression asymmetry test). Our study provided evidence that there was a significant direct association of DM and the risk of urolithiasis. However, this finding was based on the observational studies, and more well-designed randomized controlled trials were needed.