Peritoneal Protein and Albumin Excretion as Markers of Cardiovascular Risk and Systemic Endothelial Dysfunction

Abstract

Microalbuminuria is a marker of systemic endothelial dysfunction. We studied the relationship between peritoneal protein loss in peritoneal dialysis (PD) patients, which is conceptually analogous to microalbuminuria in non-uremic patients, and pre-existing vascular disease in new PD patients. Peritoneal total protein and albumin loss were quantified within 2 months of initiation of dialysis in 44 consecutive new PD patients, together with a standard peritoneal equilibration test. The results were compared according to the presence of cardiovascular disease (CVD) prior to initiation of dialysis, lean body mass, and serum albumin and C-reactive protein (CRP) concentrations. The dialysate albumin concentration was closely correlated with the creatinine dialysate-to-plasma ratio at 4 hours ( r = 0.601, p < 0.001). It was higher in patients with pre-existing CVD than in those without, when patients were analyzed according to diabetic status (one-way ANOVA, p = 0.004). In diabetic patients, the dialysate albumin concentration was significantly higher in patients with pre-existing CVD than in those without (0.754 ± 0.273 vs 1.088 ± 0.280 mg/μmol creatinine, p = 0.04). Multivariate analysis showed that only diabetic status and dialysate albumin concentration, but not peritoneal transport status or serum CRP, were independent predictors of pre-existing CVD. Although dialysate protein loss accounted for only 10.5 ± 4.4% of total protein catabolism, the dialysate protein level was significantly correlated with serum albumin concentration ( r = −0.457, p = 0.002), percentage of lean body mass ( r = −0.558, p < 0.001), and serum CRP concentration ( r = 0.434, p = 0.003). Patients with CVD prior to initiation of dialysis have higher levels of dialysate albumin and total protein excretion, indicating that dialysate protein loss is a marker of underlying CVD. Dialysate protein and albumin excretion may provide a simple and convenient measure of vascular disease and endothelial dysfunction in PD patients.