PurposeGut dysbiosis has been described in advanced, but not in initial stages of CKD. Considering the relevant impact of gut dysbiosis on renal and cardiovascular risk, its diagnosis and treatment are clinically relevant.MethodsWe designed, open-label, placebo-controlled intervention study (ProbiotiCKD) to evaluate gut microbiota metabolism in a cohort of KDIGO CKD patients (n = 28) at baseline and after a randomly assigned treatment with probiotics or placebo. Gut microbiota status was evaluated on:.ResultsBasal mean fecal Lactobacillales and Bifidobacteria concentrations were abnormally low in both groups, while urinary indican and 3-MI levels were, indicating a mixed (fermentative and putrefactive) dysbiosis. After treatment, mean fecal Lactobacillales and Bifidobacteria concentrations were increased, only in the probiotics group (p < 0.001). Conversely, mean urinary indican and 3-MI levels only in the group treated with probiotics (p < 0.001). Compared to placebo group, significant improvements of C-reactive protein (p < 0.001), iron (p < 0.001), ferritin (p < 0.001), transferrin saturation (p < 0.001), β2-microglobulin (p < 0.001), serum iPTH and serum calcium were observed only in the probiotics group.ConclusionsProbiotiCKD is the first intervention study demonstrating that an intestinal mixed dysbiosis is present even in early CKD stage and can be effectively corrected by the novel mode of administration of high-quality probiotics with improvement of inflammatory indices, iron status and iPTH stabilization.