The Continuum of Chronic Kidney Disease and End-Stage Renal Disease: Challenges and Opportunities for Chronic Peritoneal Dialysis in the United States

End-stage renal disease (ESRD) patients undergoing renal replacement therapy have a high mortality rate and suffer from considerable morbidity. Degree of nutritional decline, disordered mineral metabolism, and vascular calcification are some of the abnormalities that predict an adverse outcome for ESRD patients. All these abnormalities begin early during the course of chronic kidney disease (CKD), long before the need for maintenance dialysis. Thus, CKD represents a continuum of metabolic and vascular abnormalities. Treatment of these abnormalities early during the course of CKD and a timely initiation of dialysis have the potential of improving patient outcomes. However, the thesis that successful management of these abnormalities will favorably modify the outcomes of dialysis patients remains untested.

The proportion of incident USA ESRD patients starting chronic peritoneal dialysis (CPD) has historically been low. Limited physician training and inadequate predialysis patient education appear to underlie the low CPD take-on in the USA. Furthermore, two key changes have occurred in the USA: steep decline in CPD take-on and progressive increase in the use of automated peritoneal dialysis. The decline in CPD take-on has afflicted virtually every subgroup examined and has occurred, paradoxically, when the CPD outcomes in the country have improved. Understanding the reasons for historically low CPD take-on and recent steep declines in utilization may allow the development of plans to reverse these trends.

Is the declining use of long-term peritoneal dialysis justified by outcome data?

In the past decade, peritoneal dialysis use among patients with end-stage renal disease has declined in many countries. Studies from the United States indicate that many academic centers do not have adequate resources to train fellows, most incident dialysis patients are not offered peritoneal dialysis, and more than half of dialysis clinics do not have the infrastructure to support peritoneal dialysis. Some are concerned that the outcomes of peritoneal dialysis and maintenance hemodialysis patients may not be equivalent, a notion that is not supported by outcome studies. Given the effect of modality selection on patients' lifestyle, attempts to conduct a randomized, controlled comparison of maintenance hemodialysis and peritoneal dialysis have been unsuccessful. Most observational studies showed that peritoneal dialysis is associated with a survival advantage that diminishes over time; it is unclear whether any of the differences over time are attributable to the modality. Between 1996 and 2003, the early outcomes of peritoneal dialysis patients further improved, whereas those for maintenance hemodialysis patients remained unchanged. Differences in outcomes may be due to residual statistical confounding; however, several biologic mechanisms can be postulated: The early survival advantage may be related to the better preservation of residual renal function with peritoneal dialysis, and the diminution of the survival advantage may be related to worsened volume control. There is a need for large observational and interventional studies among peritoneal dialysis patients to sustain and enforce the improvements in both dialysis therapies.

Chronic peritoneal dialysis in the United States: declining utilization despite improving outcomes

In the United States, chronic peritoneal dialysis take-on has declined among incident ESRD patients. Although increasing age, co-morbidity, and body size may explain part of this decline, other factors likely contribute. Among incident ESRD patients in the United States, we found that peritoneal dialysis take-on significantly decreased from 11% in 1996 to 1997 to 7% in 2002 to 2003 (P < 0.001 for the trend). This decrease remained after adjusting for patient demographics, case-mix, and laboratory data, suggesting the involvement of other factors. This decline in utilization occurred during a time of improving outcomes for incident peritoneal dialysis patients, measured as reduced hazards for death or for the need to transfer to hemodialysis. In contrast, among patients initially treated with hemodialysis, the 12-month adjusted hazards for death or transfer to peritoneal dialysis slightly worsened or were unchanged over this same period. Therefore, the decline in peritoneal dialysis take-on cannot be entirely explained by increasing age, co-morbidity and body size of incident ESRD patients. The decline in utilization has occurred at a time when the early outcomes of CPD patients have improved.