Introduction

Diabetes mellitus is the fastest growing cause of end-stage renal disease (ESRD). Among patients requiring renal replacement therapy (RRT) worldwide, diabetes has become the leading cause of ESRD. Between 1984 and 1997, the percentage of new patients starting RRT whose ESRD was due to diabetes increased from 27% to 42.9% in United States [1].

The first and two-year mortality for diabetic patients in PD between the years 1989 to 1998 have been decreased by 26.6% and 20% per 1000 patient years, respectively [1]. Similar improvement has also been observed in our diabetic patient population in Toronto [2]. However long-term mortality rates in diabetic patients are still twice as high as in nondiabetic dialysis patients and actuarial rates of patient and only a small number of diabetic patients on PD have been followed for more than 5 years.

This may be due to that diabetic patients are vulnerable to considerable morbidity, which has been linked to diabetic nephropathy neuropathy and retinopathy. These devastating complications that increase with age and duration of diabetes as well as the presence of various comorbid conditions at the start of dialysis, may increase diabetic patients’ morbidity and mortality rates.

Comorbidity at the initiation of dialysis

Diabetics are at a higher risk of developing concurrent illnesses than the general population, while among ESRD patients, comorbidity is more common in diabetic than in nondiabetic patients. The presence, at the initiation of RRT, of a variety of comorbid conditions such as peripheral vascular disease, cerebrovascular disease, cardiovascular disease, hypoalbuminemia and hyperparathyroidism, may adversely affect outcomes and increase the mortality of diabetic patients undergoing dialysis.

Technique Survival Results of diabetic patients on PD

Although peritonitis remains the major cause of "drop out" (discontinuation of CAPD) among all CAPD patients, there is no evidence that diabetic patients are at increased risk of peritonitis and catheter-related infection. In our study [2], technique survival rates for the first, third, and fifth year of CAPD treatment were 93%, 72%, and 44% respectively; type 1 diabetic patients had better technique survival than type 2 diabetic patients.

Survival of diabetic patients on CAPD

The published [2–15] short-term survival rates for diabetic PD patients range from 74% – 95% (mean: 85%) for the first year, 52% – 84% (mean: 71%) for the second year, and 37% – 72% (mean: 51%) for the third year. After the third year, the reported [2–4,6–12,15] survival rates for diabetic patients on CAPD vary from 17% – 72% (mean: 39%) for the fourth year of survival and from 19% – 63% (mean: 35%) for the fifth year (Figure 1). These values are markedly lower than those of non-diabetic patients undergoing CAPD (Figure 2).

Survival comparison of diabetic ESRD patients on PD and HD

Numerous studies of dialysis populations with varying proportions of diabetic patients attempted to compare long-term clinical outcomes between PD and HD. Despite a disparity in results, most medium and long-term studies concluded that the overall survival rates of patients undergoing peritoneal dialysis and hemodialysis are not statistically significantly different [4,16–19]. Other studies favoured HD [20–22] or PD [23–25], (Table I). It must be noted that whenever an adjustment was made for comorbid factors, the comparison between the two dialysis modalities either showed no statistically significant difference or favoured CAPD.

Table 1. Comparison of long-term survival between continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD), from studies including varying proportions of CAPD diabetic patients

Collins et al [25] evaluated incident Medicare patients from 1994–1996. They used Poisson regression and compared death rates, adjusting for age, sex, race, and primary renal diagnosis. They showed that CAPD/CCPD patients have outcomes comparable to or significantly better than HD patients, although results varied with time. The Cox regression showed a lower mortality in diabetic patients less than 55 years of age on PD (either CAPD or CCPD) than on HD. In contrast, the risk of death (all causes) for female patients with diabetes who were 55 years of age and over was 1.21 for CAPD/CCPD; the risk was lower (1.03) in male patients 55 years of age and over. A more recent reanalysis by Krishnan [26] of the HD versus PD mortality in Canada showed that the previously reported results were holding true over the period from 1990 to 1998 with 7,581 patients on PD and 18,031 on HD. The overall adjusted mortality rate ratio (RR) for PD relative to HD was 0.85 (95% CI 0.81 – 0.89), whereas for the diabetic patients the differences were significant only for younger (< 64 years) males (RR 0.80 (0.71 – 0.91)). Diabetic females on PD had a significantly higher mortality rate than males in both age groups, whereas in non-diabetic females on PD the significantly higher mortality rate than males was seen in the ³ 65 years age group.

In general comparisons of clinical outcomes in HD and PD diabetic patients have been marked by inconsistent results depending on the population studied and the methods used.

Conclusion

Although several clinical studies have evaluated the factors affecting survival rates of diabetic dialysis patients, only a few studies have followed diabetic PD patients for more than five years. Moreover, despite the more sophisticated statistical methods being used to compare survival rates -either for diabetic patients between the two major dialysis modalities, or between CAPD patients with and without diabetes-methods and patient selection biases conceal potential problems, influence results, and make comparisons difficult. The higher incidence of multiple comorbid factors at dialysis initiation, older age, nutritional status, and technique limitations over the long-term (such as episodes of peritonitis, ultrafiltration "failure," loss of residual renal function, inadequate dialysis, and the peritoneal membrane failure) may shorten PD longevity in ESRD patients with diabetes mellitus undergoing CAPD. However, as long as the peritoneal membrane maintains its ability to adequately purify blood for a long time, CAPD remains a viable form of long-term renal replacement therapy for diabetic patients with end-stage renal disease.

References

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Corresponding author:
Ploumis S. Passadakis, MD,
26 Vizvizi Street, Alexandroupolis, Greece.
ploumis@hol.gr