Influence of residual renal function on dialysis adequacy in patients with continuous ambulatory peritoneal dialysis

Objective:To evaluate the influence of residual renal function (RRF) on dialysis adequacy in patients with continuous ambulatory peritoneal dialysis (CAPD). Methodology:One hundred and thirty patients, who were initiated on CAPD between Oct 2002 and Jan 2006 and completed at least 6 months of CAPD, were enrolled in this study. 608 times of observation were performed in those 130 stable CAPD patients to determine the relationship between the RRF and dialysis adequacy. The residual GFR (rGFR), Urea Kt/V, creatinine clearance (Ccr), Cardiothoracic ratio and left ventricular end-diastolic diameter index (LVEDDI) was examined, and the influence of RRF on dialysis adequacy in PD patients was evaluated. According to the rGFR, all of patients were divided into three groups. The rRRF 4ml/min were C group, 2-4 ml/min were B group, and 2 ml/min were A group. Results:There was a significant relationship between the RRF and the urea total Kt/V and total Ccr (r=0.62-0.84, P0.05). Among three groups, the significant differences were observer in rRRF, total Ccr and total Kt/V (P0.001). In C group, the percentage of rRRF contributing to clearance reached 45.7% of total Kt/V and 65.3% of total Ccr, and in B group, the percentage of rRRF contributing to clearance reached 27% of total Kt/V and 47.3% of total Ccr, while it was less than 20% of total Ccr and urea Kt/V in the A group (P0.001). Among three groups, except the significant differences in rRRF, total Ccr and total Kt/V, there was also significantly different in the level of serum albumin and cardiothoracic ratio, respectively (P0.001). However, there was no significant difference in blood pressure and LVEDDI. We found that patients with diabetes mellitus or lupus nephritis were associated with faster decline of rRRF. When the patients with urine volume less than 300ml/d would also be induced rRRF decreasing for short time. Conclusion: rRRF play a key role in maintenance of fluid balance, biochemical homeostasis and PD adequacy status. Therefore it must be keeping in mind that the dose and osmotic load of dialysis would be adjusted on patient's rRRF and body surface area.