MO713: Changes in Peritoneal Water and Solute Transport in the First 2 Years of Peritoneal Dialysis: A Prospective Study
Authors: Roldão Marisa , Escoli Rachele , Gonçalves Hernâni , Ferrer Francisco , Vila Lobos Ana 
Published: May 2022

Abstract

BACKGROUND AND AIMS
The reduction of peritoneal removal of salt and water over time is an important cause of dropout in peritoneal dialysis (PD). The aim of this study was to analyse changes of fluid and solute transport parameters in incident PD patients over the first 2 years of treatment, using the peritoneal equilibration test (PET).

METHOD
Prospective single-center study of incident PD patients who underwent 4-h 3.86% glucose PET with additional measurement of ultrafiltration at 1 h, at 3 timepoints: 1 month after PD initiation, 1 and 2 years later. Classical parameters of peritoneal transport such as dialysate-to-plasma ratio of creatinine (D/Pcreat) and ultrafiltration (UF) were analysed over time. In addition, the absolute dip of dialysate sodium concentration (ΔDNa) at 1 h, as an expression of sodium sieving, free water transport (FWT), small-pore ultrafiltration (SPUF) and sodium removal were also studied. Cancer antigen 125 (CA-125) was also assessed. Clinical and demographic data were collected. Statistical analysis was performed using SPSS (Version 23 for Mac OSX).

RESULTS
Twenty-five patients were recruited: 17 (68%) were male and 8 (32%) were diabetic. Eighteen patients (72%) were on automated peritoneal dialysis. Mean age was 56.76 ± 9.65 years. One month after PD initiation, membrane characteristics were: D/P = 0.68 ± 0.09, UF at 4 h = 0.91 ± 0.36 L, SPUF = 0.33 ± 0.14 L, FWT = 0.22 ± 0.08 L, %FWT = 50.22 ± 11.33%, sodium removal = 42.88 ± 17.72 mmol/L and ΔDNa = 11.24 ± 3.9 mmol/L. Mean serum CA-125 was 47.34 ± 21.78 U/mL. One year later, ΔDNa showed a statistically significant decrease of 1.80 ± 2.77 (P = 0.003), %FWT of 9.01 ± 12.97% (P = 0.002) and sodium removal an increase of 13.29 ± 0.20 mmol/L (P = 0.032). SPUF also showed an increase of 0.08 ± 0.20 L and UF at 4 h a mild decrease of −0.01 ± 0.61 L, however, without statistical significance. D/Pcreat showed an increase of 0.04 ± 0.11 and CA-125 a decrease of 3.30 ± 20.37 U/mL although not statistically significant. Thirteen patients completed the 2-year follow-up. From second to third PET, only ΔDNa and FWT showed statistically significant reductions of 0.54 ± 1.36 (P = 0.003) and 0.03 ± 0.05 L (P = 0.031), respectively. SPUF (−0.10 ± 0.19 L), sodium removal (−13.55 ± 27.37 mmol/L), UF at 4 h (−0.21 ± 0.55 L) and CA-125 (−1.22 ± 12.54 U/mL) also decreased over this time but did not reach statistically significance. D/Pcreat (0.01 ± 0.09) presented a mild increase.

CONCLUSION
In our study, during the first year of PD there was an increase in water and solute transport through small pores, which balanced an early drop in water transport across aquaporins, keeping UF stable. From the first year onwards, transport across small pores also began to decrease, making UF decline more evident. Early reduction of ΔDNa as a sodium sieving measure suggests that fibrosis may begin soon after PD initiation and indicates that ΔDNa can be used to access fibrotic peritoneal alterations earlier than other conventional parameters such as D/Pcreat.