Cachexia is common in patients with chronic kidney disease (CKD) and is associated with increased morbidity and mortality. Cachexia is a complex syndrome, in which inflammation and retention of uremic toxins are two main contributing factors. In this context, the role of the gut microbiome in CKD cachexia and the potential benefit of increasing the dialysis dose have been poorly explored. Here the investigators propose to study the links between cachexia and the gut microbiome, in association with inflammation and uremic toxins, in dialysis.

The specific objectives are the followings:

1. Set up a prospective cohort of deeply characterized kidney failure patients treated with hemodialysis (in-center, self-care dialysis in a satellite unit and at home) and peritoneal dialysis, including evaluation of cachexia, body composition, collection of feces and blood to characterize the gut microbiota, measure serum levels of uremic toxins and inflammatory markers, with a longitudinal follow-up.
2. To compare cachectic versus non-cachectic dialysis patients in terms of gut microbiota, inflammatory markers, level of uremic toxins, muscle transcriptome, dialysis dose and modality. In a subgroup analysis, the investigators plan to compare the different techniques of dialysis (in-center vs home-hemodialysis vs peritoneal dialysis).

Inclusion Criteria:

• Age ≥ 18 years
• Diagnosis of kidney failure (stage V)
• Maintenance dialysis for at least 3 months
• Understanding of the trial procedures and ability to adhere to the trial protocol

Exclusion Criteria:

• Severe nonadherence to the dialysis procedure
• Life expectancy below 1 year
• Chronic inflammatory disease of the digestive tract (Crohn's disease, ulcerative colitis)
• Bariatric surgery
• Active cancer
• Pregnancy
• Antibiotics consumption in the month preceding the inclusion
• Gastro-intestinal surgery, colonoscopy, or probiotics consumption in the 3 months preceding the inclusion
• Drugs influencing body composition initiated ≤ 1 month : systemic corticosteroids, anabolic drugs as insulin or testosterone, post-menopausal hormone therapy, injectable contraceptives.
• Known endocrinological disorders potentially leading to hypo- or hypermetabolism, untreated or treated for ≤ 1 month : disorders of thyroid gland, adrenal glands...
• Patients under weight loss drugs : GLP1 agonists, orlistat

The patient population studied is adult kidney failure patients treated with hemodialysis (in-center, self-care dialysis in a satellite unit or at home) or with peritoneal dialysis for more than 3 months.

The principal investigator, who is a Nephrologist and works at the Nephrology Department, in Cliniques universitaires Saint-Luc, in contact with dialysis patients, will check patient eligibility, collect the consent from the subjects who agree to participate and allocate an ID number.