This single-center randomized controlled trial evaluated the effects of natural probiotic and synbiotic supplementation on clinical and biochemical characteristics in adults with end-stage renal disease receiving maintenance hemodialysis at the Urology and Nephrology Center, Mansoura University, Egypt. Participants were randomized into three groups (control, probiotic, and synbiotic), with supplementation given for 6 months in the intervention groups. The study assessed changes in uremic toxins (including p-cresyl sulfate) as the primary outcome, and cardiovascular parameters, quality of life, and cognitive function as secondary outcomes. The trial aimed to determine whether modulation of gut microbiota with probiotics or synbiotics can improve outcomes in hemodialysis patients

End-stage renal disease patients receiving hemodialysis commonly have intestinal dysbiosis and accumulation of gut-derived uremic toxins. Probiotic and synbiotic supplementation may help modulate gut microbiota and reduce uremic toxin burden, but direct comparative data between probiotic and synbiotic strategies in hemodialysis patients are limited. This study was designed to assess the effects of natural probiotic and synbiotic administration on the clinical and biochemical characteristics and uremic toxin levels of hemodialysis patients at the Urology and Nephrology Center (UNC), Mansoura University, Egypt.

This was a single-center randomized controlled trial with single-blind allocation. Sixty adult patients with end-stage renal disease on regular hemodialysis were included (dropout-inflated sample size; calculated minimum sample size was 48). Participants were randomized into three groups: a control group (20 patients), a probiotic group (20 patients), and a synbiotic group (20 patients). The probiotic and synbiotic groups received supplementation for 6 months; the synbiotic intervention included natural probiotic supplementation combined with prebiotic fibers (oat). Regular hemodialysis was standardized during the trial (3 sessions/week, 4 hours/session).

The primary outcome was the effect of probiotic and synbiotic supplementation on uremic toxin levels, including p-cresyl sulfate. Secondary outcomes included cardiovascular-related parameters and comorbid clinical measures, including body mass index, anemia/ESA resistance, quality of life, and cognitive function. Assessments included laboratory testing (biochemical parameters and uremic toxins), echocardiographic evaluation by blinded cardiologists, and psychological assessment using cognitive testing (MOCA) and quality-of-life evaluation (KDQOL-36).

The completed thesis reports that both probiotic and synbiotic supplementation reduced serum p-cresyl sulfate compared with control, with a more pronounced reduction in the synbiotic group, and that some cardiovascular and quality-of-life parameters improved, while cognitive and other secondary outcomes were less pronounced. Baseline characteristics were comparable across groups, supporting successful randomization.

Inclusion Criteria:

• Adults aged 18 years or older.
• End-stage renal disease patients on regular maintenance hemodialysis
• Not under active preparation for kidney transplantation within the next year (i.e., not planned for transplantation for more than one year)

Exclusion Criteria:

• Age less than 18 years
• Under active preparation for kidney transplantation
• Pregnancy
• Active malignancy
• Known structural gastrointestinal tract disease

Individual participant data (IPD) will not be shared because the dataset contains sensitive clinical information collected for a single-center academic thesis, and consent and local ethics approval did not include public IPD sharing. Aggregate results will be reported in the thesis and related publications.

This was a single-blind randomized trial. Outcome assessors were blinded to group assignment. Echocardiography was performed and interpreted by cardiologists who were unaware of the intervention allocation.