MO688: Peritoneal Protein Clearance, Inflammation, Nutrition and Overhydration in PD Patients: Looking for the Culprit
Authors: Malho Guedes Anabela , Calças Marques Roberto , Ribeiro Brigitte , Fernandes Mónica , Faísca Marília , Silva Ana , Bragança José , Rodrigues Anabela 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Peritoneal protein loss has been for many years seen as a detrimental consequence of peritoneal dialysis (PD). Many studies correlated this leakage with mortality, malnutrition and inflammation. More recent knowledge has brought overhydration to this equation. This study aims to review classic and recent factors associated with peritoneal protein clearance and its consequences on overall mortality.

METHOD
Prevalent and incident PD patients were included. Interleukin 6 (IL-6; dialysate and serum) was obtained during a 3.86% glucose peritoneal equilibration test. Hydration and nutritional status was assessed by bioimpedance. Linear and Cox regression were performed.

RESULTS
A total of 78 patients were included (54 incident, 24 prevalent), the mean age was 54.6 ± 18.1 years, 65% were males, and the mean follow-up was 33.9 ± 29.3 months. The mean Charlson comorbidity index (CCI) was 4.4 ± 2.4. The residual GFR was 6.7 ± 3.6 mL/min/1.73 m2 and the D/P creatinine 0.65 ± 0.12. The IL-6 concentration in the dialysate was 24.9 ± 30.8 pg/mL and in serum was 37.3 ± 5.1 pg/mL. The phase angle was 5.4 ± 1.1°, overhydration 0.88 ± 0.94 L and peritoneal protein clearance 85.6 ± 54.7 mL/24 h. Overall, eight patients died.
Linear univariable analysis showed positive associations between peritoneal protein clearance and (i) small solute transport, as measured by D/P creatinine, (ii) body composition, as measured by phase angle and overhydration and (iii) CCI. The peritoneal protein clearance also correlated positively with dialysate IL-6, but not with serum IL-6. By linear multivariable analysis, using the backward method, a significant positive association between peritoneal protein and overhydration (P &lt; 0.001; IC:26.665–71.694) and also phase angle (P = 0.032; IC: 1.845–39.330) were validated.
In the exploratory survival analysis, no relationship was found between mortality and peritoneal protein clearance. A univariable positive association was shown with serum IL-6 concentration, overhydration and CCI. A higher phase angle was associated with lower mortality. No relationship with dialysate IL-6 or D/P creatinine was found. In this early-stage PD population, with globally preserved residual kidney function, an effect of this variable on mortality was not evident.
Cox regression, conditional backward method, showed CCI (OR: 1.896, IC: 1.235–2.913, P = 0.003), overhydration (OR: 10.034, IC: 1.426–70.587, P = 0.021) and peritoneal protein clearance (OR: 0.576, IC: 0.339–0.978, P = 0.041) were predictors for mortality.

CONCLUSION
A better nutrition status and overhydration are the major determinants of peritoneal protein clearance. The survival analysis showed that mortality is higher in overhydrated patients, with higher CCI, but not with higher peritoneal protein clearance. Inflammation, local or systemic, as assessed by IL-6 concentration, did not reveal to be such a strong prognosis predictor as overhydration in these PD patients.