DKK3 as a Biomarker of Peritoneal Fibrosis in Peritoneal Dialysis Patients

Peritoneal dialysis (PD) uses the peritoneal membrane as a natural filter to remove waste products from the blood in patients with kidney failure. Over time, the peritoneal membrane can become scarred and less functional - a process called peritoneal fibrosis - which eventually leads to ultrafiltration failure and loss of the PD technique. Currently, there is no reliable early biomarker to detect this process before it causes clinical problems. PERIMARK is a prospective, single-center, observational study investigating whether DKK3 (Dickkopf-3), a protein involved in fibrosis signaling, can serve as an early biomarker of peritoneal membrane deterioration. DKK3 will be measured in urine, peritoneal dialysate and serum at four time points over 12 months (T0: catheter insertion; T1: 12 weeks; T2: 6 months; T3: 12 months). At each follow-up visit, peritoneal membrane function will be assessed by the Modified Peritoneal Equilibration Test (Modified PET) with 3.86% glucose, measuring the sodium dip (ΔDNa) as a marker of aquaporin-1-mediated water transport and D/P creatinine as a marker of small solute transport. The primary endpoint is the intraindividual change in DKK3/creatinine ratio in urine, dialysate and serum from baseline to 12 months. Secondary endpoints include the correlation of DKK3 with the sodium dip, longitudinal changes in peritoneal transport parameters, and the exploratory question of whether an early DKK3 rise predicts a later decline in aquaporin-1 function. The study also includes a biobank of serum, urine, dialysate supernatant and cell pellets for possible future analyses. Target enrollment is 25-30 patients.