ABSTRACT

Technological advances including those that allow the delivery of an adequate dialysis dose to a larger percentage of patients, and minimization of peritoneal membrane damage with more biocompatible solutions, along with lower peritonitis rates, will undoubtfully improve retention of patients on PD for longer periods. Currently only 15% of the world dialysis population is managed by PD. Peritoneal dialysis has many advantages over hemodialysis and if ESRD patients are fully informed about them, the proportion of patients who would prefer this treatment will rise to 25%-30%.

An integrated approach to the treatment of ESRD could start with peritoneal dialysis in a large percentage of patients, especially those who will receive a kidney transplant within 2-3 years. In the present epidemic of ESRD, this approach could lead to a significant saving, relieve the pressure on dialysis units and allow a larger number of ESRD patients being treated.

INTRODUCTION

Until kidney transplantation becomes widely available, patients with end-stage renal disease (ESRD) who require renal replacement treatment (RRT) will have to be maintained on either hemodialysis (HD) or peritoneal dialysis (PD). Various medical, social and demographic factors make one treatment preferable to the other.

Since its introduction by Popovich and Moncrief in 1975, CAPD and various forms of automated peritoneal dialysis (APD) have established themselves as acceptable alternatives to HD and, since then, the use of PD has been increasing steadily throughout the world. In 1998 approximately 120,000 ESRD patients were maintained on various forms of PD worldwide.

Utilization of PD varies among various countries depending on such local factors as reimbursement issues, availability of HD, distance from a center, physician and nurse biases etc. Thus, in the USA, 13% of ESRD patients were on PD in 1998. The corresponding figure in Canada is 37%, United Kingdom 42%, Mexico 91%, Hong Kong 81% and Japan 6% [1].

This paper will concentrate on patient and technique survivals, morbidity, quality of life, some medical aspects such as rate of decline of residual renal function (RRF), cardiovascular complications, post-transplant course and dialysis costs. We believe that a review of the advantages and disadvantages of each treatment and knowledge of the comparisons between the two modalities will assist physicians, nurses, patients and their families in making a decision about what treatment to select.

However at the onset it should be emphasized that these two modes of dialysis should be considered complementary with each other and along with transplantation provide the ESRD patient the best treatment alternative at each particular time of his/her life. Only a team that has extensive experience with each treatment alternative can provide its patients with a long life of high quality.

PATIENT SURVIVAL

A number of factors, such as age, diabetes, comorbid conditions, malnutrition, dialysis dose etc. may affect survival.

Therefore, when comparing the data on survival of the two modalities, one has to take into account all these factors, through a multivariate analysis. Furthermore, we should consider country-related differences such as revealed by the CANUSA study in which "being dialyzed in the USA" was one of the highest risk factors with a 93% increase in relative risk of death among those dialyzed in the USA compared to those dialyzed in Canada [2].

Recently Davies et al reviewed patient survival among long-term cohorts on PD patients for the decade between 1988 and 1998, and reported a five-year patient survival ranging between 35 and 60% (Table I), while technique success at 5 years varied between 55-72%. The majority of studies in PD patients do not provide detailed information as to how PD patients die. The best data describing the cause of death comes from Italian studies, in which sudden or cardiovascular deaths account for 45 to 47%, cachexia and malignancy for 23 to 25%, sepsis for 12 to 13%, and miscellaneous causes comprising the rest [3,4]. In their paper Davis et al described the mode of 106 consecutive deaths. Of the total number of deaths, 58% occurred when the patient was on PD and 42% after transfer to hemodialysis or transplantation.

Comparisons Between PD and HD Survivals In 1995 Bloembergen et al compared cohorts from the period - 1987 to 1989.

Using prevalent patients and Poisson regression model, they found an increased death rate among patients on CAPD relative to those on hemodialysis (RR=1.19, p<0.001); the difference was statistically significant for patients older than 55 years. The mortality risk was especially significant for older patients both those who were diabetic (RR=1.38, p<0.001) and those non-diabetic (RR=1.11, p<0.001).

This study, which was based on 170,700 patient-years of experience, covered 93% of prevalent U.S. HD and PD patients treated between 1987-1989 inclusive [5].

A criticism of this study is that the case-mix analysis considered only diabetes but no other comorbid factors. A higher comorbidity in one group would bias the results against that group. Undoubtedly the publication of this paper aroused serious concerns about the future of PD, even though analysis of a large number of Canadian patients by Fenton et al. showed, if anything, that PD patients in all categories (diabetics-elderly etc.) showed a better survival at least for the first two years.

Fenton's study, which was based on data from the Canadian Organ Replacement Register (CORR), included patients who started RRT between 1990 and 1994. These authors studied incident patients and used the Poisson regression analysis, which compensated for switches in mode of treatment; they found a significantly lower risk of death in PD patients across the various age groups and in diabetics. For ages 0-64 years, the relative risk (RR) of death was 0.54 for non diabetic PD patients (RR for HD being 1), and 0.73 (95% confidence interval, 0.68 to 0.78) for diabetics. The RR was 0.76 for non diabetics over 65 years of age and 0.88 for diabetics over 65 years [6].

In a subsequent analysis of the U.S. Renal Data System (USRDS), Vonesh et al studied mortality rates for patients treated with PD versus HD in the United States for the cohort periods 1987-to 1993 and showed a gradual improvement in PD moralities between 1989-1992; indeed the differences between HD and PD disappeared, except in older female diabetics, who still had higher mortality on PD. For the average male diabetic patient, there was little or no difference in risk between PD and HD from 1989-1993. For diabetic patients under age 50, those treated with PD had a significantly lower risk of death, than those treated with HD (1989-93: RR £ 0.89, p<0.005). Over the same period, female diabetics had a higher risk on PD than on HD (RR = 1.19, P< 0.001), as did diabetics over the age 50 (RR £ 1.30, P< 0.001).

These authors concluded that, by studying both prevalent and incident patients they found little or no difference in overall mortality between PD and HD [7].

A recent analysis of the US data by Collins et al. supports Fenton's observation concerning the higher survival of PD patients during the first two years with subsequent equalization of mortality of the two treatments thereafter. In this study, PD was associated with a significantly lower risk of death (RR=0.61 to 0.88) in all patients except diabetics older than age 55 years; in the latter group, the RR for men was comparable with that of hemodialysis (RR=1.03) and the RR for women was 21% higher. (RR=1.21).

Regarding diabetic patients, death rates followed similar trends in both women and men; Collins et al concluded that, within the first two years of follow up, nondiabetics and younger diabetic patients have a significantly better overall outcomes on CAPD/CCPD than on hemodialysis [8].

The narrowing in the mortality differences between HD and PD in the USA over the years is probably due to the increased awareness of the importance of the residual renal function and the need for individualized peritoneal dialysis prescription in large and especially anuric patients. Furthermore better control of hypertension and fluid overload with more frequent use of APD, have also played a role in the improvement of the result of PD patient. Of course a lower comorbidity among PD patients mean also amount for better survival results and that adjustment for all comorbit conditions may eliminate the superiority of PD survival as a recent Canadian study showed (9).

An even more recent analysis of 432 patients in the USA showed again that after adjustment of comorbidity, survival on PD equals or is even better than that on HD, particularly among blacks in whom the difference is maintained up to 7 years of treatment (10).

A recent paper by Schaubel et al analyzed a population of 17,900 patients, who received PD between January 1, 1981 and December 31, 1997 in Canada. Approximately 37% of patients were in the 45-64 age group upon PD initiation while about 36% were >65 years of age. The unadjusted mortality rate was 184.8 per 1000 patient/year during 1981-1997 and decreased steadily, from 230.2 deaths per 1000 patient/year during the 1981-1985 period (RR=1) to 162.2 deaths per 1000 patient/year RR=0.70 (0.64 to 0.77 95% CI) for the 1994-1997 period. They observed much stronger trends when data were adjusted for age, race, gender primary renal disease and follow-up time. The RR values decreased with calendar time, each successive period experiencing a lower mortality than the previous one.

Adjusted mortality rates decreased significantly by calendar period. The reduction in mortality was significant for each calendar period within each subgroup i.e. non diabetic patients age < 64, and for diabetic patients < 64 while for diabetic patients > 65 of age the changes between 1986-1989 (RR=1.01, P=NS) and 1981-1985 [serving as the reference period (RR = 1, fixed)] the differences where not significant [11].

We conclude from the above review that there is a little difference in the mortality between the two modalities except for the slightly higher mortality among elderly female diabetics in the USA.

Technique Survival

Technique survival is usually lower in CAPD/APD than HD. The reported 50% technique survival on PD ranges from 3 to 5 years compared to 60-75% on HD over the same period. Similarly the number of patients maintained for longer than 7 years on PD, is below 10% compared to 40% - 50% on HD. [12]

Davies et al, who reviewed technique survival cohorts between 1988 - 1998, found a five-year technique survival over this decade of 55-70% - levels that approached those of hemodialysis [3].

Causes of Technique Failure

Recurrent or severe peritonitis episodes (especially those due to S. aureus, pseudomonas or fungi), are important causes of technique failure; this is particularly true if the peritonitis persists and the catheter has to be removed and the patient is treated "temporarily" by hemodialysis [13].

Ultrafiltration failure is the next most important cause of technique failure. It occurs with increasing frequency as the duration of PD increases [3,14]

Other causes include difficulties with the catheter, patient/family fatigue and malnutrition/calhexia. Sclerosing encapsulating peritonitis is a fatal complication that occurs with an increasing frequency as the duration of treatment increases; usually this is preceded by ultrafiltration failure [15].

Once patients with any of these complications switch from PD to HD, their survival is lower compared to that of those who remain on PD. Five-year actuarial survival for patients, who switched therapies, were lower (32% Vs 58% for peritonitis , p=0.005; and 38% Vs 58% for ultrafiltration failure, p=0.3) when compared to those who remained on PD . Those who switched because of malnutrition did worse than any other group (27% survival at 2 years vs 78% for those who remained on PD during the same period, P=0.005) [3,16] and therefore when switch to HD is considered patients should be transferred before malnutrition develops. Table III shows the causes of technique failure reported in five studies between 1991 and 1998. Long-Term Survival on CAPD

Only a small percentage of CAPD patients remain on this treatment for 10 years or more. The percentage of those who stay on CAPD for 10 years varies from 1% to 10 % among various centers. The characteristics of those who survive on PD for long periods are: young age, predominance of women, few commorbid condition at start, low weight or body surface area and low incidence of peritonitis or other complications [17,18]. Low BSA and infection rate indicate the importance of adequate dialysis and control of peritoneal infection in achieving long term PD-survival.

Development of new dialysis solutions such as those with neutral pH, non-glucose osmotic agents or agents that will improve inflammatory response may further improve long-term survival over the next decade [19]. Quality of Life (QoL)

The definition of QoL is difficult because it embraces dimensions ranging from physical well being, cognitive competence, satisfactory inter-relationships and sexual function, enjoyable occupation at work or home and possession of sufficient income to explore the world beyond that necessary for basic biological survival [20]. Unquestionably one of the goals of ESRD treatment is to allow the patient maximum psychosocial maturation and development, while at the same time helping them to adapt to the stress of therapy.

The commencement of HD or CAPD appears to trigger a decline in functional status and mobility. Patients starting dialysis also experience an increase in psychological and sexual problems, a reduction in social activities, and an increase in marital problems. [21]

Overall patients on home dialysis modalities such as CAPD/APD enjoy better health than those on hospital-based treatment, which almost certainly contributes to a better QoL. In a study by Morris and Jones, CAPD patients had an improved quality of life compared to in-center HD patients. With regards to employment status 35% of CAPD patients were employed compared to 19% of in-center HD patients [22].

Nissenson et al., confirmed these findings and also showed that CAPD patients appeared to make a superior psychosocial adaptation to their situation than did in-center HD patients. This may be due to the fact that usually CAPD attracts patients who want autonomy and want to take control of their health care, and of their lives. Also those who want to continue their jobs often prefer to be on PD [23]. In a multicenter study of 250 patients Merkus et al. found that HD patients showed lower levels of QoL than PD patients in terms of physical functioning (PF) (51 vs 61, P<0.05), role functioning emotional (RP) (28 vs 31, P=NS), mental health (MH) (63 vs 72, P<0.05) and pain (BP) (64 vs 73, P<0.05).

The results are reported on a scale of 0 to 100 with a higher score indicating a better quality of life [24].

In another study Mercus et al, showed that HD patients had lower levels of subjective well-being for physical functioning, mental health and pain.

When analyzed in a multivariate model, dialysis modality had an impact only on mental health. When the same population was analyzed on a longer term basis (18 months) the difference in subjective well-being between PD and HD tended to disappear (25).

However other studies that compared QoL between dialysis patients did not show that any one mode of treatment was superior to another.

These inconsistencies may have been due to small sample size, and the cross-sectional design of the studies. The latter produces heterogenous treatment groups with respect to the duration of therapy and divergent therapy history. Additional factors that may contribute to inconsistent results include insufficient control of background characteristics and the use of different definitions and different instruments of assessment tools of QoL [26,27]. It should be emphasized all studies on QoL attempting to compare the two modalities are not randomized and potential for selection bias is profound. Hospitalization

Studies that have compared hospitalization rates and days spent in hospital annually between PD and HD patients are difficult to compare because of differences in individual centers' policies regarding hospitalization, the availability of outpatient care and social facilities, and the close attention to cost-savings. Other factors that make comparisons between two groups difficult are the different case-mixes of the populations studied, the influence of age and diabetes on hospitalization rate and the different causes for hospital admission. Finally it is important to know whether the study includes the first hospitalization for training in dialysis [28].

Generally HD patients have a lower hospitalization rate than those on PD; among the latter, the main cause for hospitalization is peritonitis [29].

Analysis of the USRDS data showed that hospital admissions and the number of hospital days per year have been declining since 1991.

This decline is more marked for CAPD than for HD patients; perhaps it is secondary to declining peritonitis rates [30]. In earlier studies, peritonitis - a major cause of hospitalization accounted for 23% to 37% of the admissions and five to 10 hospital days per patient year. Recently Fried et al., reported that the admission rate of PD patients was 1.6 per patient year and hospitalization rate was 13.0 hospital days per patient year [31].

After adjustment for differences in patient characteristics (age, sex, presence of diabetes etc.), it appears that hospitalization rates for blacks versus whites and for those older than 60 years versus those younger than 60 were not significantly different. The admission rate was higher in men than in women (1.8 versus 1.5 admission per patient year; P<0.05). Patients with diabetes have a higher admission rate (2.2 versus 1.4 admissions per patient year; P<0.001), and a greater number of hospital days than non-diabetic patients (18.1 versus 10.9 days/pt. year; P<0.001).

Recently Collins et al performed an interval Poisson regression on incident Medicare CAPD/CCPD (23,767 patients) and HD (128,346 patients) from 1993 to 1996, with follow-up through 6-30-97, assessing the relative risk of all-cause first hospitalization in the follow-up period. They concluded that hospitalization risk at 3 months was 0.61 to 0.81 (P<0.002) in CAPD/CCPD patients, which may reflect higher early HD vascular access hospitalization. In the follow-up period CAPD/CCPD was not different from hemodialysis with regards to all causes of hospitalization. [32]

In another study Collins et al showed that hospitalization for cardiac reasons in diabetic CAPD/CCPD patients was not different from hemodialysis patients (RR:0.84 to 1.18, P=NS). Non diabetic CAPD/CCPD patients had 11 to 31% significant lower cardiac hospitalization risk (RR;0.84 - 0.97, 95% CI, P<0.05) compared to hemodialysis patients, except for non diabetic males age 20 to 44 (RR:0.95, P=NS) and patients (males and females) 75 years and older (RR:0.88 to 0.97. P=NS) who had a similar risk.

Patient selection bias may contribute to these findings. [33] Residual Renal Function

Residual renal function (RRF), when present, makes an important contribution to small and large molecule clearances, facilitates fluid balance, allows the patients to have a more liberal diet and fluid intake and reduces the risk of dialysis-related amyloidosis.

Following the initial observation of Rottenbourg and his associates, several other groups have observed that RRF is maintained better in CAPD patients than in those on HD [34,35].

There may be several possible reasons why RRF is better preserved in CAPD than in HD patients. Thus CAPD might provide positive hemodynamic stability with less abrupt fluctuations in volume and osmotic load and less modification in hemodynamic status; this may be associated with a more stable glomerular capillary pressure, leading to a more constant glomerular filtration. [36,37]

Furthermore CAPD patients probably consume a lower protein intake which might be nephropotective while the HD process produces a higher volume of cytokines, which may damage the residual renal function [38].

Residual renal function contributes significantly to the survival of CAPD patients and better preserves their nutritional status. Several studies have examined the relative contribution of RRF to Kt/Vurea and to weekly creatinine clearance normalized to body surface area (nKcr). [39] These show that RRF has a great influence on adequacy indexes. In 64 CAPD patients, who were treated with CAPD 2 litres X 4 exchanges per day,

Heimburger et al found that RRF accounted for 25% of Kt/Vurea and 38% of nKcr. Furthermore, the total (peritoneal plus renal) of Kt/Vurea and nKcr showed a strong correlation with 24-hour urinary volume (r=0.65and r=0.68 respectively, p<0.001). This strong correlation is not unexpected because dialysate urea concentration is close to equilibration with plasma for a substantial part of the CAPD dwell time and thus the RRF will have a great impact on the interindividual differences in Kt/Vurea (because all patients were treated with the same dialysate volume). [40]

The CANUSA study indicates that each 5 liters per week of RRF brought a 5% reduction in the relative risk of death.[2]

The better preservation of RRF in CAPD patients has important clinical implications. It can be assumed that, in the presence of a preserved excretory renal function, the non-excretory endocrine function also will be better preserved, thus maintaining erythropoietin synthesis, converting vitamin D to its active form, and giving a better elimination of b2 microglobulin. Reportedly serum b2 microglobulin levels are lower in PD patients with RRF, and several workers have demonstrated an inverse correlation between serum b2 microglobulin levels and serially measured creatinine clearances or residual diuresis [2,41,42,43]. It is hypothesized that biologically active substances, involved in the progression of glomerular sclerosis are eliminated by PD and not by HD, because of their high M.W. or because of protein binding.

Thus Niwa et al has shown that indoxylsulphate, one of the many circulating uremic toxins, stimulates the progression of glomerular sclerosis and is eliminated, at least in part, by PD. [44,45] Cardiovascular Disease

Recent studies to evaluate contrasting effects of HD and PD on cardiac function, suggest that CAPD has hemodynamic advantages over HD, due primarily to minimal variation in intravascular volume and reduction of cardiovascular stress based on the absence of an arteriovenus fistula. Also hypertension is common in dialysis patients and undoubtedly contributes to the development of cardiovascular disease. Approximately 80% of patients are hypertensive at the initiation of dialysis; however, in hemodialysis the prevalence falls to 25 to 30% and in peritoneal dialysis to 40% by the end of the first year largely due to better blood volume control [46].

The early correction of hypertension in both peritoneal and hemodialysis patients and the observation that low blood pressure in the presence of heart failure (a strong predictor of mortality), probably explains why hypertension was not an independent risk factor of death in most of the comparative studies [47].

Left ventricular hypertrophy and left ventricular geometry have a distinct impact on mortality in both hemodialysis and peritoneal dialysis patients.

Besides left ventricular hypertrophy a high prevalence of left atrial dilatation and abnormal left ventricular diastolic filling have been found in CAPD patients (48,49,50). Using echocardiography in a study of 16 CAPD patients with normal systolic function followed for an average of 35 months, Huting and Acpert reported an increase in LV mass from 251g to 342g and a decrease in LV volume mass from 0.73 to 0.54. [48] Predictors of LVH were higher mean blood pressure and higher cardiac output. Eisenstein et al had previously reported progression of LVH in CAPD patients due primarily to inadequate control of systolic blood pressure. [49] Studies by Franklin et al demonstrated that dialysate volumes in excess of 2L may produce impairment of systolic function in patients with severe LVH. The clinical significance of these observations is uncertain at this time [50].

Recent studies have addressed the issue of diastolic LV function in CAPD patients. Huting et al performed echocardiography and cardiac Doppler studies on 48 CAPD patients. Twenty five patients (52.1%) had LV hypertrophy (defined as LV wall posterior thickness > 13mmHg) and 23 (47%) had an LV posterior wall thickness. Also a "trial filling fraction" was significantly greater in CAPD patients without LV hypertrophy than in CAPD patients with LV hypertrophy or non renal failure hypertensive patients [51]. These results suggest that LV diastolic dysfunction is common in CAPD patients with and without LV hypertrophy, but is more consistently abnormal in those with LV hypertrophy. LVH is also common in HD patients. Thus Dahan et al who studied 80 hemodialysis patients treated for more than 6 months, found that sixty two patients (78%) had LVH. Forty one patients had no or mild LVH (i.e. LVM of less than 175gr/m2 in men and less than 150gr/m2 in women) and 39 patients had severe LVH [52].

However in many of the above studies, a variety of methods are used to calculate LVM and volumes and the formula used to calculate LVM overestimates values in patients with substantial left ventricular dilatation.

Dyslipidemia also is a risk factor for cardiovascular disease and CAPD is associated with a more atherogenic lipoprotein profile than is HD. PD patients have more adverse lipid profiles than HD patients with higher levels of cholesterol, triglycerides and LDL. [53] However Avram et al found that in PD patients, there was no correlation between lipid profiles and cardiovascular risk. [54] This might be due to the fact that hypocholesterolemia can be a sign of malnutrition which is an independent risk factor for mortality in PD patients. Several authors have found that LP(a) levels were an independent risk factor for cardiovascular events. [55,56] However, LP(a) is also related with malnutrition and inflamation and these factors may be the real culprits for the observed increase in cardiocascular risk. [57] New PD solutions may block mechanisms that cause lipid abnormalities in CAPD patients. Jones et al. have shown that amino-acid-containing solutions can be used to replace amino-acid-protein losses into dialysate, and that might have a beneficial impact on lipids [58]. Gokal et al., also have shown that use of icodextrin solution could reduce glucose load and improve the lipid profile in PD patients. The addition of icodextrin, once a day, produced a decline in total cholesterol and LDL after six months [19].

Despite the atherosenic profile that would make one believe that CAPD/CCPD will have a higher mortality rate and heart failure than HD, recent review by Collins et al of the mortality risks of PD and HD patients concluded that "both male and female non-diabetic patients on CAPD/CCPD had lower risk of cardiac mortality" than those on HD. Also on CAPD both diabetic men and women had a lower risk of cardiac death compared to those on HD. [8]

PD is particularly useful in patients with congestive heart failure. Its advantages include excellent and continuous ultrafiltration, prevention of arrhythnias better volume and blood pressure control, which may lead to regression of left ventricular hypertrophy and better control of anemia (although, with the use of erythropoietin, this is not so critical).

Complications of Peritoneal Dialysis Access Related

Infections are a frequent cause of morbidity and hospitalization for both dialysis modalities.

In peritoneal dialysis exit site infections, especially those due to s.aureus have been decreased significantly with the use of Mupirocin at the exit-site. [59] Similarly the overall peritonitis rates have decreased significantly after the introduction of the various disconnect systems to levels of 1/24-1/36 patient months. However this improvement involves mainly the mild cases of peritonitis whereas the incidence of the serious ones i.e. fungal, pseudomonas, other gram negative have remained at the same rates, fortunately a lower one.

A frequent complication in both HD and PD is malnutrition.[2] Both hypoalbuminemia and a decrease in lean body mass or subjective global assessment are strong predictions of poor outcome. [60]

Though a low protein and calorie intake may contribute to malnutrition, recent investigation [61] has indicated a strong correlation between malnutrition and inflammation and possibly atherosclerosis (MIA Syndrome). Therefore treatment of malnutrition with increased protein and calorie intake will be ineffective in the presence of inflammation that can be rejected by an increase in CRP.

Similarly, malnutrition can develop in underdialyzed patients and restoration of an adequate (or even increased) dose of dialysis should be the first step in the treatment of malnutrition. Intraperitoneal aminoacids have a place in such patients once the question of adequacy has been addressed.

Inadequate dialysis usually is of a concern in large muscular patients, especially when they become anuric. However, recent developments such as increase use of large exchange volumes (2.5L or 3L) and a combination of APD at night with one or two day exchanges will provide adequate dialysis in almost any size of patient. One should also remember that overweight obese patients do not necessarily require a corresponding increase in the dialysis dose because their volume of body water (v) is not proportionately increased; because fat tissue does not carry water as muscle tissue. CAPD and the Elderly

Only few studies have compared the survival of elderly patients on PD and HD. The Canadian experience indicate that on PD the non-diabetic elderly have a lower mortality than those on HD. In diabetics, the mortality rates were similar [6]. In a recent analysis of USA data, Collins et al [8] showed that, among diabetics older than 55, the risk of death was similar with the two modalities but, among women older than 55 on PD, it was higher by 21%.

Elderly patients on HD frequently have difficulties with vascular access, have more intradialytic complications and often require cessation of dialysis to control hypotension [62].

Finally CAPD/APD offers a better option for elderly patients living in a nursing home or those living away from the center, especially if they have some assistance from home-care nurses trained in the simple technique of CAPD/APD. CAPD and Transplantation

The use and selection of alternative modes of treatment in ESRD particularly the difference in the rate of transplantation among countries, could distort the results of these comparisons.

From country to country, the ratio between the number of patients transplanted per year varies widely ranging from 3% in Japan, to 25%-29% in the US and in Canada [63]. Although initial experience suggested that renal transplantation might be hazardous for PD patients, due to the risk of peritonitis and to a possible high incidence of rejection, we now know that global results of renal transplantation are similar in patients on PD and HD [64]. Perez Fontan et al compared 56 transplanted PD patients with 58 transplanted HD patients. PD patients had received fewer blood transfusions (5.8 ± 5.6 Vs 9.2 ± 8.6, p<0.05), and were transplanted after a shorter cold ischemia time than HD patients (19.4 ± 6.8 Vs 22.3 ± 7.5, p <0.05).

Initial graft function was present in 76% of PD patients versus 50% of HD patients (p<0.05). In addition the time until dialysis independence was 7.8 ± 3.9 days in PD patients versus 16.8 ±8.0 days in HD patients (p<0.025).

They found no significant differences between the two groups regarding hospitalization for renal transplantation (p<0.1 NS), or regarding technical or medical noninfectious complications (0.62/patient in PD group Vs 0.77/patient in HD group). Finally the incidence of early infection (first month) was similar in both groups (0.57/patient in PD group Vs 0.48/patient in HD group). [65]

Compared to HD patients, patients on PD, who undergo renal transplantation, show a lower incidence of delayed graft function, suffer a lower incidence of infections, and have a similar incidence of dialysis-related complications. [66]

With regards to cadaveric kidney transplantation many studies have demonstrated that PD, compared to HD, has a beneficial effect on the immediate recovery of renal function. [67,68] In a study by Van Biesen et al, the incidence of acute renal failure, of delayed graft function and of the need for post transplantation dialysis was lower in the patients treated with peritoneal dialysis as pre-transplantation dialysis modality. [69]

Hepatitis C infection

The prevalence of anti-HCV among patients on dialysis is higher than in a healthy population, ranging from 8% to 36% in North America, 39% in South Africa, 10% to 54% in Europe and 17% to 51% in Asia. In Saudi Arabia, the prevalence of anti-HCV among HD units ranged from 15.4% to 94.7% [70].

There is a steady decline in the overall incidence and prevalence of HCV infection among patients on dialysis due to reduction in post - transfusion HCV infection. Centers that compared the prevalence of anti-HCV in PD and HD patients have observed a consistently lower prevalence of anti-HCV among PD patients [71].

In a group of 129 anti-HCV-negative patients on chronic dialysis, the rate of seroconversion was 0.15/patient - year on HD compared with 0.03/patient - year on PD patients (p<0.05). Furthermore, most HCV - positive PD patients may have acquired HCV infection while on HD [72].

Indeed, Huang et al reported a 15.4% prevalence of HCV among PD patients. However, when patients with prior HD were excluded, the prevalence decreased to 5.9% [73]. Factors that account for the lower risk of HCV infection among PD patients include a lower requirement for blood transfusion in PD than HD patients and the absence of an access site and extracorporeal blood circuit, which reduce the risk to exposure to the virus. Finally, because PD is primarily a home procedure, it offers a more isolated environment. Indeed, the prevalence of HCV in patients receiving home HD is also lower than those receiving center - HD [74].

HIV Infection

The incidence of HIV infection has been rising worldwide. Six to 10% of HIV-infected patients show renal manifestations of HIV infection and 40% of these patients will require renal replacement therapy (RRT) [75]. The prevalence of HIV infection among dialysis patients varies widely among different countries and within different regions of each country. A large multicenter study involving dialysis units in 12 US states, observed a 0.3% to 2.6% prevalence of HIV-infection [76]. The current prevalence of HIV infection among dialysis patients in the US is approximately 1.5%.

Likewise, the prevalence of HIV-infection among dialysis patients ranges from 0%-5% in European countries, 5% to 7% in Puerto Rico, 1.6% in Egypt, and 2.2% in Brasil [77]. The choice of RRT often is based on patient preferences and feasibility; CAPD offers the advantages to staff of a lower risk of occupational exposure to HIV and a lower risk to patients of acquiring hospital-associated communicable diseases. Kimmel et al reviewed the effectiveness of CAPD for HIV-infected patients and found no difference in mean survival time between patients treated with HD (14.7% ± 9.7% months) versus PD (17.9% ± 10.7% months) [78]. In contrast, Schoenfeld et al found a better survival among patients who where able to perform CAPD (median, 31months) compared with patients on HD (median, 12 months, p<0.05). [79] However there may be a selection bias since those who performed CAPD might have been clinically better being able to perform home-dialysis modality.

Difficulties in HIV infected patients on PD are related to infections (peritonitis) and protein loss in an already immunocompromised asthenic patient. CAPD/APD HIV infected patients have a higher incidence of fungal infections. [78] Finally CPD is potentially beneficial RRT for HIV infected patients and has advantages for both patient and technical staff. However routinely every PD unit should undertake universal precautions with barrier protection, disinfection and sterilization strategies. Costs

Many studies have demonstrated that peritoneal dialysis is significantly cheaper than in-center hemodialysis. Usually automated peritoneal dialysis is more expensive than CAPD and, depending on the volume of dialysate used, may approach the cost of home or self-care hemodialysis [80].

In countries where peritoneal dialysis solutions must be imported e.g. South America, India etc. all forms of peritoneal dialysis cost more than hemodialysis.

Pommer et al calculated that total annual costs (supplies, nursing, medication, hospital costs, overhead costs) reached about 32.411 ECU for PD versus 46.020 ECU for HD, meaning that 3 patients could be treated on PD for the cost of 2 patients on HD. [81] Rublee et al reviewed some cost-evaluating studies comparing HD and PD and concluded that PD is more economic than HD, but that the magnitude of the difference may vary between countries. [82] Another crucial factor in analyzing costs is that hospitalization charges account for nearly 41% of the total costs of dialysis therapy. Careful attention to adequate out-patient dialysis delivery and maintenance of optimal nutrition will substantially reduce hospitalization costs [83]. Dratwa calculated that in Belgium in 1996, the average total costs for a patient on HD was 1.130.064 BF (28.040 Euro) per year. These costs include the cost for nursing, technicians, depreciation of machines, dialysate and logistical support. For a PD patient, the average total cost was about 702.520 BF (17.419 Euro) [84]

We believe that, in a capitated environment, PD will have an advantage over HD. Interaction of Renal Replacement Therapies in the Treatment of ESRD Patients

Although successful transplantation offers the best quality of life and, for certain groups of ESRD patients, a better survival, dialysis is still required for those waiting for transplantation, those who are not good candidates or do not want a kidney transplant, and for those with a transplant failure. [85]

If one takes into account the advantages of each mode of dialysis, one can adapt each treatment to the needs of a particular patient at a particular time of their ESRD life, resulting in the longest survival with a high quality of life at the lowest cost.

Recently Van Biesen et al, who analyzed their experience with 417 patients (223 on HD and 194 on PD), concluded that an integrated care approach in which patients start on PD and are transferred to HD when problems arise, does not jeopardize patient outcome. These authors believe that this approach can improve RRT availability in a growing ESRD population and in the face of budgetary restrictions. [86]

It is important not to delay the transfer to HD, if complications develop, since PD patients with hypoalbuminemia transferred to HD have a higher mortality rate. [87] In a recent paper by Woodrow et al, regarding outcomes included patients survival and technique failure (with change to hemodialysis being considered as technique failure) showed that after changing to HD, survival rate of PD patients following CAPD failure was only 61% at 1 year. A contributing factor to the high mortality after treatment failure may have been the effect of nutrition, with a significantly lower serum albumin immediately after change to dialysis modality (32.4±4.7 gr/L, compared with patients remaining on CAPD at the end of follow-up or before transplantation, 37.4±4.0 gr/L, P<0.0001). [88].

Conclusion

The nephrologists should take into account all the advantages and disadvantages of both peritoneal and hemodialysis in order to best meet the needs of the patient with end stage renal disease. Such a balanced approach will lead to longer patient survival with improved quality of life at a lower cost.

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