Dietary salt restriction during conservative therapy may prevent declines in residual renal function for the first year after starting peritoneal dialysis in patients with end-stage renal diseases

Background: Preservation of residual renal function (RRF) is an important factor in achieving adequate peritoneal dialysis (PD) therapy for patients with end-stage renal disease (ESRD). We investigated whether dietary salt restriction was effective during conservative therapy as a factor to prevent decreased RRF after starting PD therapy. Methods: We retrospectively observed 30 patients introduced to PD in a single center. To investigate the relationship between effects of a salt diet and decreased RRF in PD patients for the first year after starting PD, we divided patients into two groups according to salt intake before starting PD therapy: Group 1, <6 g/day; and Group 2, ≥6 g/day. Sodium intake was calculated using samples from 24-hour urinary collection and/or 24-hour peritoneal dialysate collection. Results: Before starting PD, residual renal Kt/V (rKt/V) and CCre (rCCre) were significantly lower in Group 1 than in Group 2 (p<0.001 and p<0.005, respectively). Normalized protein-equivalent of nitrogen appearance was also significantly lower in Group 1 than in Group 2 (p<0.001), suggesting that Group 1 might also maintain good control of protein. Moreover, compared with Group 2, decline rates in rKt/V and rCCre during the first year were significantly lower in Group 1 (p<0.005 and p<0.001, respectively). Conclusion: Our results suggested that restricting salt intake was not only important to preserve RRF during the conservative therapy period in ESRD patients, but also might be important to prevent early decreases in RRF among PD patients.