Relationship between residual renal function, inflammation, and anemia in peritoneal dialysis

In peritoneal dialysis (PD) patients, we analyzed the relationship between residual renal function (RRF) and well-known predictors of mortality such as anemia, inflammation, and nutrition. We also investigated possible associations between the foregoing parameters and cardiovascular comorbidity, peritoneal transport rate, statin and antihypertensive treatments, and ultrafiltration volume. Our study enrolled 24 patients (17 men, 7 women; mean age: 56 +/- 12 years) who had started PD at our hospital between 1998 and 2004. Patients who had been hospitalized or had had peritonitis before the study were excluded. Nutrition status, inflammation, anemia, RRF and dialysis adequacy were assessed after 1-2 months. We found that RRF was positively correlated with normalized protein equivalent of nitrogen appearance (nPNA: r = 0. 52, p = 0. 03) and negatively correlated with C-reactive protein (CRP: r = -0.47, p < 0.01) and peritoneal ultrafiltration (r = -0.42, p < 0.05). Only the nPNA and CRP correlations remained statistically significant on multivariate logistic regression analysis (CRP: r = 0.8, p = 0.011; nPNA: p = 0.013). Moreover, as compared with patients without inflammation, patients with inflammation had significantly lower hemoglobin (Hgb) levels (11.8 +/- 1.1 g/dL vs. 13.2 +/- 1.2 g/dL, p < 0.02), serum prealbumin levels (27.3 +/- 8 mg/dL vs. 36.6 +/- 9 mg/dL, p < 0.05), and serum transferrin levels (168 +/- 34 mg/dL vs. 202 +/- 31 mg/dL, p < 0.05), and a higher erythropoietin resistance index (ERI: 10 +/- 4 vs. 6 +/- 3.5, p < 0. 02). We observed no differences in RRF or nutrition status between the patients with high and with low peritoneal transport. Regarding comorbidity, patients with pre-existing cardiovascular disease had higher CRP levels (0.8 +/- 0.4 mg/dL vs. 0.4 +/- 0.4 mg/dL, p < 0.05) and lower mean Hgb levels (13.3 +/- 1 g/dL vs. 14.4 +/- 1 g/dL, p < 0.05) than did patients without such pre-existing disease. A strong, predictable association exists between RRF and inflammation and nutrition status in incident patients on PD. Serum CRP is a good indicator of inflammation, which correlates well with nutrition status, anemia, and responsiveness to erythropoietin therapy.