Assessment of Early GFR, Tubular Function and Pathology Changes Early and Late After Renal denervatioN

The purpose of this clinical study is to better understand how renal denervation (RDN) affects kidney function, both shortly after and up to a year after the procedure. Renal denervation is a minimally invasive treatment used for patients with high blood pressure that does not respond well to medication ("resistant hypertension"). It works by reducing the activity of nerves that run along the arteries supplying the kidneys, which helps lower blood pressure. To understand how RDN affects the kidneys, we will measure kidney function in detail and analyse blood and urine samples collected before and after the procedure. This will help researchers see whether the procedure causes changes in the kidneys, and whether some of these changes are linked to better kidney health over time.

Inclusion Criteria: * ≥18 years * eGFR \>30 ml/min/1.73m2 (CKD stages 3b and less severe) * Informed consent for study participation provided by the patient or the legal guardian * Patient information and consent to the processing of personal data * Stable therapy in the previous three months * All patients undergoing RDN for clinical indications Exclusion Criteria: * Patients in emergency situations * Turbid urine sample on admission * Visible haematuria in the urine sample on admission * Pregnancy * Allergy to contrast media (visipaque, omnipaque, iohexol) * Any problem, which, in the investigator's opinion, might jeopardize the participant's compliance with the protocol.