Sodium toxicity in peritoneal dialysis: mechanisms and "solutions"

The major trials in peritoneal dialysis (PD) have demonstrated that increasing peritoneal clearance of small solutes is not associated with any advantage on survival, whereas sodium and fluid overload heralds higher risk of death and technique failure. On the other hand, higher sodium and fluid overload due to loss of residual kidney function (RKF) and higher transport membrane is associated with poor patient and technique survival. Recent experimental studies also show that, independently from fluid overload, sodium accumulation in the peritoneal interstitium exerts direct inflammatory and angiogenetic stimuli, with consequent structural and functional changes of peritoneum, while in patients with Chronic Kidney Disease sodium stored in interstitial skin acts as independent determinant of left ventricular hypertrophy. Noteworthy, this tissue pool of sodium is modifiable being removed by dialysis. Therefore, novel PD strategies to optimize sodium removal, including the use of bimodal and/or low-sodium solutions, are actively tested. Nonetheless, a holistic approach aimed at preserving peritoneal function and the kidney may represent the key of therapy success in the hard task of preserving adequate sodium balance in PD patients. In this review, we describe the available evidence on sodium toxicity in PD, either related or unrelated to fluid overload, and we also discuss about possible "solutions" to preserve or restore sodium balance in PD patients.