The goal of this observational study is to learn about the role of thoracic and whole body bioimpedance in the hemodynamic profile of patients with chronic kidney disease.

The main question it aims to answer is:

- Is bioimpedance-determined fluid status associated with kidney function decline in patients with chronic kidney disease stage 3 - 5 (non dialysis).

Participants will be measured during their regular visit to their treating nephrologist.

During a follow up of one year, 3 or 4 visits will be scheduled.

• Bioimpedance and blood pressure measurements will be achieved by non-invasive techniques.
• Blood sampling will as much as possible coincide with regular blood samplings for clinical purposes.
• All subjects will undergo echocardiography at baseline and after one year follow up.

Inclusion Criteria:

• Prevalent non-dialysis patients with estimated glomerular filtration rate < 60 ml/min (for chronic kidney disease subjects)
• Age > 18 years
• Signed informed consent

Exclusion Criteria:

• Acute kidney injury
• estimated glomerular filtration rate < 20ml/min directly post-nephrectomy
• Clinical conditions affecting bioimpedance measurements: limb amputation, impaired skin integrity, brain stimulator, pacemaker with low threshold or unipolar pacemaker.
• Clinical conditions affecting body composition: liver cirrhosis, active infectious disease or any acute cardiovascular event (defined as cerebrovascular event, myocard infarction, heart failure) during the 3 months before screening for inclusion
• Pregnancy

206 patients with CKD stages 3-5 will be included from the outpatient clinic of Ziekenhuis Zuid-Oost Limburg in Genk (Belgium).

A healthy control group for the cross-sectional part will be recruited through visitors and/or personnel of Ziekenhuis Oost-Limburg in Genk (Belgium).