Serum vitamin D levels and acute kidney injury: a systemic review and meta-analysis.

Numerous researches have evaluated the prevalence and clinical outcome of vitamin D deficiency in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). But the quantitative vitamin D status in acute kidney injury (AKI) patients and its relationship with prognosis remains controversial. We conducted this systemic review and meta-analysis to assess the quantitative difference of vitamin D status, including serum 25(OH) D and 1,25(OH)2D levels, between AKI patients and non-AKI controls, and further explore whether vitamin D status can be clearly correlated with the mortality of AKI. Major databases, including PubMed, Web of Science and EBSCO, were searched until 1st September 2021. All published observational studies related to vitamin D and AKI According to predefined inclusion and exclusion criteria were extracted. Meta-analyses were performed using Review Manager 5.3.5. Four studies including five cohorts were included with a total of 413 patients. The serum 25(OH)D levels showed no statistically significant difference in AKI patients and non-AKI controls. On the other hand, the serum 1,25(OH)2D levels were significant lower in AKI patients than in non-AKI controls (MD =  - 17.79, 95% CI =  - 32.73 to - 2.85, P = 0.02). As for the relationship between serum vitamin D status and AKI patients' mortality, we were unable to give a consistent conclusion based on current limited and conflict study results. Our meta-analysis suggested that serum 1,25(OH)2D levels, rather than 25(OH)D, is significantly lower in AKI patients. The relationship between vitamin D status and clinical outcome of AKI remains controversial based on current evidence. Future comprehensive studies are required to confirm these relations and to elucidate potential mechanisms.