Cognitive function and uremic toxins in patients with severe renal failure: a pilot study

A vast proportion of patients on dialysis still suffer from the uremic syndrome
despite achieving their dialysis targets. The uremic syndrome can be defined as
a modification of biochemical or physiologic functions as a result of the
accumulation of a large number of compounds due to a deficient renal clearance.
As a consequence uremic complaints in this population (i.e. anorexia,
inflammation, and cardiovascular diseases) are not uncommon. In addition, we
noticed the presence of cognitive disorders in this group of patients. This is
supported by literature demonstrating that dialysis patients present with mild
to moderate impairment in multiple domains of cognitive function. On the
contrary, transplant patients show normal or near normal cognitive function. We
hypothesize that uremic toxins play a major role in the development of
cognitive impairment, and therefore, we expect that decreasing uremic toxin
levels will improve cognitive function.
The aim of this study is to assess the degree of cognitive impairment in
dialysis patients in comparison with non-dialyzed patients with renal
insufficiency and to determine to what extent this impairment improves after a
kidney transplantation. In addition, we want to investigate which (group of)
uremic toxins are associated with developing cognitive impairment.
If the contributing uremic toxins can be determined, it is conceivable that
modifying the uremic toxins levels, i.e. by dietary adaptations or probiotics,
could improve cognitive function in patients on dialysis.

Primary Objective:
- to determine cognitive impairment in patients with severe renal failure

Secondary Objective(s):
- to determine to what extent this impairment improves after a kidney
transplantation
- to evaluate changes in uremic toxins after transplantation

This is an observational cohort and pilot study in which several
neuropsychological tests, examining the main cognitive domains (intelligence,
memory, attention and concentration, executive functions) and suboptimal
performance (i.e. malingering), will be performed in three different groups of
patients with severe renal insufficiency. In addition to the neuropsychological
tests, four questionnaires will be used to assess subjective cognitive
complaints, quality of life, mood, and the degree of fatigue.
In addition, blood samples will be drawn from the patients in order to
determine the presence of uremic toxins.

The neuropsychological tests and questionnaires will be administered by a
trained neuropsychologist. The blood samples will be taken by trained nurses.

Participants will be subjected to a neuropsychological assessment 3 times. Each
assessment will take 1,5 hour and will be administered during either a regular
outpatient clinic visit or hospital admission. In addition, participants will
be asked to fill in four questionnaires that will take about 15 minutes to
complete. Finally, an extra sample of blood will be drawn during regular blood
taking moments.