Sodium removal by peritoneal dialysis: a systematic review and meta-analysis

Achievement of sodium and fluid balance is considered a major determinant of dialysis adequacy in peritoneal dialysis (PD). However, the contribution of different PD modalities to dialytic sodium removal (DSR) remains ill-defined. We performed a systematic review and meta-analysis to compare DSR by manual (continuous ambulatory PD, CAPD) versus automated PD (APD). Alternative PD strategies to remove sodium were also analyzed. Seven cohort studies, including 683 patients, 406 in CAPD and 277 in APD, were meta-analyzed out of the 30 studies selected based on DSR data availability. Overall, the unstandardized mean difference between CAPD and APD was significant [- 56 mmol/day (95% CI - 106, - 6), p = 0.027]. Heterogeneity was high (I² 87.2%; p < 0.001). Meta-regression showed a strict correlation of DSR difference with creatinine dialysate/plasma ratio (D/P) (p = 0.04). DSR was significantly lower in APD than CAPD [86.2 (57.3-115.1) vs. 141.3 (107.6-174.9) mmol/day, p = 0.015]. Conversely, ultrafiltration (UF) did not differ [1122.6 (891.2-1354.0) in CAPD and 893.6 (823.0-964.2) ml/day in APD, p = 0.064]. A very strong correlation between DSR and achieved UF was found in CAPD (R = 0.94; p < 0001) while no relationship was detected in APD (R = - 0.07; p = 0.85). CAPD allows a higher DSR than APD, even though UF is not different. APD removes more water than sodium; therefore, DSR should be measured rather than estimated from the achieved UF. The difference in DSR between the two modalities decreases in high transporters. Novel strategies proposed to increase DSR, e.g. lower sodium dialysate or adapted-APD, are promising, but ad hoc studies are necessary.