Chronic kidney disease (CKD) is characterized by a irreversible decrease of kidney functions. It is characterized by accumulation of solutes called uremic toxins. Uremic toxins levels are implicated in cardiovascular complications associated with CKD. Several protein-bound toxins have been implicated in the increased cardiovascular risk such as indoxyl sulfate (IS), p cresol sulfate (pCS) and more recently the indole acetic acid (IAA). All clinical studies are performed with a single measurement at baseline assuming that the toxin levels are stable over time. The variability of uremic toxins level is not known. Furthermore, little is known concerning determinants of serum toxins level.

Colonic absorption play a major role in IS (indoxyl sulfate) and pCS level. IS and pCS level are significantly reduced in patient with colectomy. To validate the measurement of uremic toxins level in serum as biomarkers for cardiovascular risk, we need to know about intra-individual variability over time and the impact of diet or digestive disorders on uremic toxin serum level. We propose a prospective study evaluating the intra-individual variability in 3 uremic toxins serum levels the SI, the pCS and IAA.

The main objective is to study the kinetics of three serum uremic toxins: the indoxyl sulfate, p cresyl sulfate and indole acetic acid (and thus determine the intra-individual variability) in a population of chronic hemodialysis patients during 1 year.

Inclusion Criteria:

• Major subjects of both sexes aged 18 and over
• Topics affiliates or beneficiaries of a social security scheme
• Haemodialysis patients whatever the etiology of renal failure for more than 3 months
• Patients not under antibiotic
• Agreeing to participate in the study and who signed a consent
• Patient able to understand a written questionnaire

Exclusion Criteria:

• Pregnant or lactating women
• Detainees
• Adults under legal protection or unable to consent
• Patient's refusal to sign the informed consent for participation
• Possibility of recovery of renal function (eg scleroderma)
• Patients carrying a replicating viral infection (HCV, HIV).
• Taking antibiotics in the previous month by 1 sampling