Peritoneal Dialysis Should be the First Choice of Initial Renal Replacement Therapy for More Patients With End-Stage Renal Disease

Ganter 1 performed the first peritoneal dialysis (PD) in a human being in 1923, long before any clinical hemodialysis was done. However, only when the problems of securing long lasting access to the peritoneal cavity were resolved, 2 and the concept of continuous ambulatory peritoneal dialysis (CAPD) were introduced 3 and tested, 4 did PD become a viable treatment for individuals with end-stage renal disease (ESRD). The therapy saw phenomenal growth for almost two decades and, at the end of 1997, it was estimated that there were 115,000 patients on PD worldwide. 5 Even then, wide disparities in the use of PD were noted between countries and within different regions of the same country. 6 These differences have stimulated a wide range of investigations, and it can be reasonably concluded that in most of the cases, nonmedical factors dictate the choice of dialysis modality. 7–11 Yet, beginning with the mid-1980s and up until the mid-1990s, nearly 14% of all incident and prevalent patients with ESRD were being treated with peritoneal dialysis. 12 During the past 5 years, while the absolute number of patients being treated with PD has remained constant in the United States (US), the proportion of incident and prevalent patients on PD has declined to approximately 10%. 12 This has been a cause for tremendous concern among the supporters of peritoneal dialysis, and we present our thoughts about the process and why we believe it is incumbent upon the nephrology community to reverse the trend. We want to take this advocacy a step further and propose that PD could be and should be the first choice of dialysis therapy for many more patients commencing maintenance dialysis than is reflected by current practises. Peritoneal Dialysis in the United States: Forever the Stepchild The utilization of PD in the US has never exceeded 14–15% of the incident or prevalent patients with ESRD. 12 Is there evidence that the therapy is under utilized? Not only do we believe that such is the case, our belief is shared by practicing nephrologists in the US and Canada. A recent survey of US nephrologists conducted by Mendelssohn et al.13 with 240 respondents concluded that if survival, wellness, and quality of life were the goal, they would recommend the utilization of PD in almost 33% of patients and, if cost-effectiveness were the goal, they would recommend PD for 40% of patients. In an earlier survey, Canadian nephrologists had echoed similar sentiments. 14 This would seem to suggest that the practice in Canada is close to what is perceived as optimal by Canadian nephrologists, whereas the practice in the US is far from what US nephrologists consider optimal. What are the reasons behind these major discrepancies? We believe that deficits in patient education and physician training explain substantial proportions of the difference. The diagnosis of ESRD is a life altering event for the patient. Many hours are needed to educate patients about the disease process and the options for renal replacement therapy. Several studies have demonstrated that a patient who is referred to a nephrologist early 10,15,16 and is educated about his/her options 11,17,18 is more likely to choose a home treatment modality, particularly peritoneal dialysis. There is overwhelming evidence that a significant proportion of patients are referred late to a nephrologist, 15,16 and delayed commencement of dialysis is the norm. Under these circumstances, there is little opportunity for patient education. However, nephrologists need to share a significant proportion of blame for either providing limited or no education for the patients with ESRD. The data reported by the Dialysis Morbidity and Mortality Study, Wave 2 are shocking: only 25% of patients who chose HD reported that PD was discussed with them, whereas 68% of patients who chose PD reported that HD was discussed with them. 16 Are we systematically denying equal access to both dialytic modalities to our patients? In our opinion, these data can be interpreted in only two ways: either the educational tools and methods used by physicians for a large portion of patients who commenced maintenance hemodialysis were completely ineffective, or the nephrologists assume a patronizing role in regard to modality selection. We maintain that both of these situations are wrong and need to be rectified. There has always been a suspicion that major deficits exist in training fellows in the field of dialysis, particularly PD, in programs across the US. The results of a survey of 271 practicing nephrologists conducted by Thamer and colleagues 19 clearly suggest that major deficits in physician training may exist in the United States: while 61% of respondents reported that they received training primarily in HD, only 35% reported that they received training in both PD and HD. Hence, it is incumbent upon the nephrology community that all training programs provide training in all aspects of clinical nephrology. Is it not paradoxical that the Accreditation Committee for Graduate Medical Education insists that a training program needs to expose each fellow to at least 10 new transplants every year, while no such precise quantitative requirements exist for either HD or PD procedures. The anomaly becomes more pronounced when one considers that while only a small fraction of nephrology trainees entering practice will take care of patients within the first week of a renal transplant, almost all will take care of patients on dialysis. Indeed, almost a third or more of all nephrology practice involves care of dialysis patients. Peritoneal Dialysis: Its Time Has Come It is paradoxical that in an era in which the advantages of PD have been so well documented that the proportion of ESRD patients being treated with PD has declined. In this section, we present arguments to support our contention that PD should be the first line therapy for many more patients beginning maintenance dialysis than is currently seen, especially in the US. PD is associated with superior survival in the first few years of dialysis. During the period of 1980–1995, numerous studies were conducted that compared the survival of patients being treated with HD and PD. Although there were several studies that touted the superiority of either HD or PD over the other therapy, the vast majority of studies were unable to demonstrate any difference in survival between the two therapies. In 1995, the study from the United States Renal Data System (USRDS) by Bloembergen et al.20 demonstrated that patients treated with PD had a 13% greater risk of death than those treated with HD, and the authors attributed the higher mortality in patients treated with PD as a modality-effect. These results shocked the PD community. However, a critical review of the study design reveals that the pooling of prevalent and incident patients is a major flaw. Furthermore, using the same USRDS database, Vonesh et al.21 compared the survival of patients being treated with PD and HD in subsequent years and demonstrated that PD was associated with a similar survival to HD. The study by Vonesh rehabilitated the reputation of PD. Since then, Collins et al.22 and Fenton et al.23 have published comparative data on the survival of a large number of incident patients treated with HD and PD from the US and Canada, respectively. A consistent theme emerges from both sides of the border: in the first 2 years of therapy, all nondiabetic and young diabetic patients treated with PD have a survival advantage. The results of the two studies diverge with respect to the survival of older diabetics: while the study by Collins et al.22 reported a poorer survival in older, diabetic women with PD, the study by Fenton et al.23 demonstrated a superior survival in all sub-groups of patients studied, including older, diabetic women. Given the consistency of findings in large databases, we believe that the evidence for the superior survival for all nondiabetic and young diabetic patients treated with PD in the first 2 years of treatment is strong and noteworthy. These patient groups constitute more than two-thirds of patients that begin maintenance dialysis in the US every year, yet only 10% of patients use PD. PD is associated with superior preservation of residual renal function and forms the ideal therapy for incremental dialysis. Numerous studies, during the past two decades, have demonstrated that PD is associated with a superior preservation of residual renal function. 24–26 For years it has been argued that this could be an artifact created by informative censoring: as residual renal function is required to maintain adequate dialysis in a large proportion of patients on PD, individuals that lose residual renal function faster are more likely to be transferred to HD. However, recent data from the University of Missouri has demonstrated that even when informative censoring is taken into account, the advantage of PD, relative to preservation of residual renal function, is still suggested. 27 If the sole advantage that was accrued from the superior preservation of residual renal function was that the kidneys continued to remove water and small molecular weight uremic toxins and, hence, played an additive role to dialysis, it could be argued that for HD, with its greater efficiency, preservation of residual renal function was not important. However, there are at least two additional advantages of the better preservation of residual renal function. First, practitioners of PD have recognized and intensively studied the importance of residual renal function. To our knowledge, no evidence exists to support the thesis that residual renal function does not play an important role in patients treated with HD. In fact, several investigators have documented progressive decline in various measures of nutritional status in patients on long-term HD. 28 The relationship of this nutritional decline to changes in residual renal function needs to be delineated in future studies. Second, better preservation of residual renal function and the continuous nature of the therapy permits PD to be the ideal therapy for incremental dialysis in “healthy starters” (individuals who commence maintenance dialysis when the residual renal Kt/Vurea is approximately 2.0). Several nomograms have been constructed to determine how to practice incremental dialysis. 29 It is apparent that for patients on HD, once-weekly HD is adequate only for 5 months for most patients, and even during this period, the duration of dialysis has to keep increasing to keep pace with declining renal function. 29 Moreover, given the short-term viability of once-weekly HD, and the wide swings in serum chemistries, it is recommended that patients be started on twice-weekly HD with a switch to thrice-weekly HD at an appropriate time. On the other hand, for the patient on PD, only nocturnal exchanges are required for up to 18 months from initiation, thus allowing the patient freedom to pursue daytime activities. 29 Incremental exchanges can then be added without the need for additional retraining. Timely initiation and incremental dialysis may therefore be easier and associated with less disruption of life with PD than with HD. Patients Treated with PD have a Superior Outcome After Renal Transplantation. The advantages of preservation of renal function with the use of PD may extend beyond the period of dialysis. Evidence is accumulating that suggests that individuals treated with PD prior to transplantation have superior graft function when compared with individuals treated with HD. 30 This would make PD particularly advantageous in individuals who are likely to be on dialysis for a short period before a renal transplant is performed, as would be the case for living related transplantation. PD is Associated with Superior Salt and Water Balance and Permits a more Liberal Diet. Since the introduction of PD, it has been observed that patients treated with PD maintain a more neutral salt and water balance than individuals treated with HD. Indeed, whereas only 50–60% of patients treated with PD require antihypertensive therapy to maintain normotension, more than 90% of patients treated with HD require antihypertensive therapy. There are likely to be several reasons for these observations. First, PD is a continuous treatment modality, and salt and water removal occurs 24 hours a day, 7 days a week. On the other hand, there is only a window of 10–15 hours per week, for patients on thrice weekly HD, during which salt and water removal can be accomplished. Second, the sodium concentration used in the peritoneal dialysis solution (132 meq/L) is significantly lower than that in the dialysate used for hemodialysis (140–142 meq/L). This permits a greater amount of sodium removal. As a consequence of greater salt and water removal, the requirements for antihypertensive therapy are lower for patients on PD, and this allows a more liberal diet when compared with patients on HD. To conclude, we believe that the underutilization of PD in the US is the result of educational deficits in both nephrologists and patients. PD offers tremendous advantages in terms of survival, preservation of residual renal function, outcomes following renal transplantation, and salt and water removal. This leads us to strongly recommend PD as the first choice dialysis therapy for many more patients with ESRD than is currently being seen, especially in the US.Harbor-UCLA Medical Center and Research and Education Institute,

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