Treat Autosomal Dominant Polycystic Kidney Disease With Oral Ketone Ester? (ADKETONE)

The investigators are running a study to see if a special drink, called a "ketone ester", can help people with a type of kidney disease named "Autosomal Dominant Polycystic Kidney Disease" or ADPKD for short. The investigators want to find out: If it's easy for patients to take this drink every day for about 2 months. If it's safe and doesn't cause any problems. If it makes a difference in the size and function of the kidneys. Who can join? People between 16 to 70 years old who have ADPKD. Those with a certain amount of kidney size and function. People who haven't been on specific diets or lost a lot of weight recently. Women who are not breastfeeding and are using birth control. People with a body weight that is not too low or too high. Who cannot join? People who've been on a high-fat diet or skipped meals for a while recently. Those with other health conditions like diabetes or certain metabolic issues. Anyone who has a problem with getting an MRI scan. If participants are in another medical study right now. The study will happen in two Belgian hospitals and is supported by the UZ Brussel's nephrology department. The investigators hope to include 20 people and start in November 2023.

Repeated measures design to register the changes before and after treatment. Non-randomized, non-blinded, multi center prospective interventional cohort trial.

Objective observance (ketone body levels ≥0.8 mmol/l in ≥75% of blood measurements and ≥60% of maximal theoretic dose determined by used packages and self-report)

Patient reported feasibility, defined as a cohen d effect size of < 0.5 in the ADPKD impact scale.Both targets (observance and self-reported feasibility) must be met to reach the endpoint.

Inclusion Criteria: - ADPKD patients (diagnosis based on genetics or imaging) ≥ 16 and ≤ 70 years. Total Kidney Volume ≥ 600 mL. eGFR (CKD-EPI) ≥ 30 ml/min/1.73m2. Normal blood glucose, HbA1C and ketones. Women of childbearing potential who are non-lactating and using an effective form of birth control. Stable disease-modifying treatment for the last 2 months. Well controlled hypertension (stable antihypertensive medications for at least 2 months). BMI > 18 < 30. Written informed consent. Exclusion Criteria: Exposure to a ketogenic diet or intermittent fasting for more than 2 weeks within 6 months before inclusion. Significant weight-loss (> 10%) within 6 months before inclusion. Diabetes mellitus. Conditions prohibiting the use of a ketogenic diet (liver damage, pancreatic failure, pyruvate-carboxylase deficiency, defects in fatty acid oxidation/gluconeogenesis/ketolysis/neogenesis, hyperinsulinism), based on patient history. Diagnosis with any disorder of fatty acid metabolism based on patient history. Eating disorder. Alcohol abuse. Contraindication for MRI. Participation in other interventional trial.