Advances in peritoneal dialysis

New peritoneal dialysis (PD) patients have a better survival than new haemodialysis (HD) patients in the first years on dialysis. During long-term treatment, this changes into a survival advantage for HD. The superior initial survival on PD is related to a better preservation of residual renal function of PD patients compared to HD. The importance of residual renal function is probably due to additional properties of native kidneys, such as a better removal of organic acids and low molecular weight proteins than occurs during dialysis. The magnitude of the residual glomerular filtration rate (rGFR) in PD patients is not only associated with better survival, but also with less uraemic symptoms, such as loss of appetite, and also with higher scores on quality of life tests. These relationships are absent for peritoneal clearance. Consequently measures to preserve rGFR are extremely important. Studies on an effect of peritoneal transport status on survival have given variable RESULTS: A large meta-analysis showed that fast transport patients have a 15% increased risk of death, but this is only the case for continous ambulatory peritoneal dialysis (CAPD) with conventional dialysis solutions. This suggests that the development of overhydration may be the link between transport status and mortality. A fast transport status can be inherent or acquired. The inherent form can either be due to an inflammatory state or to a large mesothelial cell mass. In both situations vasoactive mediators may be locally released. A permanent acquired fast transport status, leading to severe ultrafiltration failure develops in about one third of the patients. It is conceivable that the excess mortality in fast transport patients is caused by the types associated with an inflammatory status and with the acquired type of long-term PD. The latter, linked to morphological peritoneal alterations, is mainly caused by exposure to conventional dialysis solutions. An icodextrin based solution is especially indicated to treat ultrafiltration failure. The aim of the ''biocompatible'' solutions is to prevent the peritoneal changes. The results of animal and clinical studies are promising so far. The objective of modern PD is to extent its initial survival advantage to long-term treatment. Recent advances in knowledge of mechanisms and new dialysis solutions are likely to make this possible