Peritoneal equilibration testing: Your questions answered

The peritoneal equilibration test (PET), first described in 1987, is a semiquantitative assessment of peritoneal transfer characteristics in patients undergoing peritoneal dialysis. It is typically performed as a 4-h exchange using 2.27/2.5% dextrose dialysate with serial measurements of blood and dialysate creatinine, urea, and glucose concentrations. The percentage absorption of glucose and D/P creatinine ratio are used to determine peritoneal solute transfer rates. It is used to both help guide peritoneal dialysis prescriptions and to prognosticate. There are several derivative tests which have been described in the literature. In this review, we describe the original PET, the various iterations of the PET, the information gleaned, and the use in the setting of poor solute clearance and in the diagnosis of membrane dysfunction, and limitations of the PET.

Automated Peritoneal Dialysis: Patient Perspectives and Outcomes

A steadily increasing number of end stage kidney disease (ESKD) patients are maintained on automated peritoneal dialysis (APD) worldwide, in long-standing as well as in more recently established peritoneal dialysis (PD) programs. A better understanding of the technique, paralleled by progress in involved technology, sustained this growth to the point that APD has become the prevalent mode of PD delivery in most high-income countries. While APD is now regarded to be at least as efficient as continuous ambulatory peritoneal dialysis (CAPD) with regard to major biomedical outcomes, its impact on patient-reported outcomes has been less investigated. This paper reviews the main outcomes of APD from a clinical point of view and from the person on dialysis perspective.

The prognosis and risk factors of baseline high peritoneal transporters on patients with peritoneal dialysis

The relationship between baseline high peritoneal solute transport rate (PSTR) and the prognosis of peritoneal dialysis (PD) patients remains unclear. The present study combined clinical data and basic experiments to investigate the impact of baseline PSTR and the underlying molecular mechanisms. A total of 204 incident CAPD patients from four PD centres in Shanghai between 1 January 2014 and 30 September 2020 were grouped based on a peritoneal equilibration test after the first month of dialysis. Analysed with multivariate Cox and logistic regression models, baseline high PSTR was a significant risk factor for technique failure (AHR 5.70; 95% CI 1.581 to 20.548 p = 0.008). Baseline hyperuricemia was an independent predictor of mortality (AHR 1.006 95%CI 1.003 to 1.008, p < 0.001) and baseline high PSTR (AOR 1.007; 95%CI 1.003 to 1.012; p = 0.020). Since uric acid was closely related to high PSTR and adverse prognosis, the in vitro experiments were performed to explore the underlying mechanisms of which uric acid affected peritoneum. We found hyperuricemia induced epithelial‐to‐mesenchymal transition (EMT) of cultured human peritoneal mesothelial cells by activating TGF‐β1/Smad3 signalling pathway and nuclear transcription factors. Conclusively, high baseline PSTR induced by hyperuricaemia through EMT was an important reason of poor outcomes in CAPD patients.

APD or CAPD: one glove does not fit all

The use of Automated Peritoneal Dialysis (APD) in its various forms has increased over the past few years mainly in developed countries. This could be attributed to improved cycler design, apparent lifestyle benefits and the ability to achieve adequacy and ultrafiltration targets. However, the dilemma of choosing the superior modality between APD and Continuous Ambulatory Peritoneal Dialysis (CAPD) has not yet been resolved. When it comes to fast transporters and assisted PD, APD is certainly considered the most suitable Peritoneal Dialysis (PD) modality. Improved patients’ compliance, lower intraperitoneal pressure and possibly lower incidence of peritonitis have been also associated with APD. However, concerns regarding increased cost, a more rapid decline in residual renal function, inadequate sodium removal and disturbed sleep are APD’s setbacks. Besides APD superiority over CAPD in fast transporters, the other medical advantages of APD still remain controversial. In any case, APD should be readily available for all patients starting PD and the most important indication for its implementation remains patient’s choice.

Icodextrin Versus Glucose Solutions for the Once-Daily Long Dwell in Peritoneal Dialysis: An Enriched Systematic Review and Meta-analysis of Randomized Controlled Trials

RATIONALE & OBJECTIVE

The efficacy and safety of icodextrin versus glucose-only peritoneal dialysis (PD) regimens is unclear. The aim of this study was to compare once-daily long-dwell icodextrin versus glucose among patients with kidney failure undergoing PD.

STUDY DESIGN

Systematic review of randomized controlled trials (RCTs), enriched with unpublished data from investigator-initiated and industry-sponsored studies.

SETTING & STUDY POPULATIONS

Individuals with kidney failure receiving regular PD treatment enrolled in clinical trials of dialysate composition.

SELECTION CRITERIA FOR STUDIES

Medline, Embase, CENTRAL, Ichushi Web, 10 Chinese databases, clinical trials registries, conference proceedings, and citation lists from inception to November 2018. Further data were obtained from principal investigators and industry clinical study reports.

DATA EXTRACTION

2 independent reviewers selected studies and extracted data using a prespecified extraction instrument.

ANALYTIC APPROACH

Qualitative synthesis of demographics, measurement scales, and outcomes. Quantitative synthesis with Mantel-Haenszel risk ratios (RRs), Peto odds ratios (ORs), or (standardized) mean differences (MDs). Risk of bias of included studies at the outcome level was assessed using the Cochrane risk-of-bias tool for RCTs.

RESULTS

19 RCTs that enrolled 1,693 participants were meta-analyzed. Ultrafiltration was improved with icodextrin (medium-term MD, 208.92 [95% CI, 99.69-318.14] mL/24h; high certainty of evidence), reflected also by fewer episodes of fluid overload (RR, 0.43 [95% CI, 0.24-0.78]; high certainty). Icodextrin-containing PD probably decreased mortality risk compared to glucose-only PD (Peto OR, 0.49 [95% CI, 0.24-1.00]; moderate certainty). Despite evidence of lower peritoneal glucose absorption with icodextrin-containing PD (medium-term MD, -40.84 [95% CI, -48.09 to-33.59] g/long dwell; high certainty), this did not directly translate to changes in fasting plasma glucose (-0.50 [95% CI, -1.19 to 0.18] mmol/L; low certainty) and hemoglobin A_1c levels (-0.14% [95% CI, -0.34% to 0.05%]; high certainty). Safety outcomes and residual kidney function were similar in both groups; health-related quality-of-life and pain scores were inconclusive.

LIMITATIONS

Trial quality was variable. The follow-up period was heterogeneous, with a paucity of assessments over the long term. Mortality results are based on just 32 events and were not corroborated using time-to-event analysis of individual patient data.

CONCLUSIONS

Icodextrin for once-daily long-dwell PD has clinical benefit for some patients, including those not meeting ultrafiltration targets and at risk for fluid overload. Future research into patient-centered outcomes and cost-effectiveness associated with icodextrin is needed.

Peritoneal Protein Loss, Leakage or Clearance in Peritoneal Dialysis, Where do we Stand?

Peritoneal protein loss (PPL) through peritoneal effluent has been a well-recognized detrimental result of peritoneal dialysis (PD) treatment since its inception. Investigation has focused mainly on PPL quantitative and qualitative determinations and evaluation of its prognostic value.

A comprehensive review of the pathophysiology of PPL (3-pore model revisited), methods of quantification, dialysate protein composition, and impact on clinical outcomes is presented herein. The author summarizes a brief analysis of associated cardiovascular disease and nutritional consequences, exploring the controversial cause-effect on mortality and technique failure.

Therapeutic modalities aiming to reduce PPL (angiotensin-converting enzyme inhibitors [ACEI]s and vitamin D therapies) were explored, although it is unclear whether PPL represents a valid therapeutic target or, on the other hand, is solely a manifestation of endothelial dysfunction.

Impact of Glucose Exposure on Outcomes of a Nation-Wide Peritoneal Dialysis Cohort - Results of the BRAZPD II Cohort

Background: Data investigating the association of glucose exposure with technique failure and patient survival are limited to retrospective cohorts and was never tested outside Asia and considering the presence of competing risks.

Methods: Prospective multicenter cohort study of incident peritoneal dialysis patients where the association of cumulative glucose exposure in 6, 12, and 24 months with patient survival and technique failure was tested using Cox regression analysis and competing risk analysis.

Results: We analyzed 4367 incident peritoneal dialysis patients with mean age 59.0 ± 15.8 years, 43.9% were diabetics, 46.7% males and 64.4% Caucasians. Glucose exposure was not associated with patient survival independent of the time of exposure and even after adjustments for confounders. In contrast, higher glucose exposure was associated with more technique failure in the Cox and competing risk models. The higher risk for technique failure was found in the subgroup exposed to the higher amount of glucose to a maximum of 86% in the model analyzing cumulative glucose exposure for 1 year.

Conclusion: Glucose exposure was associated with technique failure but not with patient survival.

Membrane transport status does not predict peritonitis risk in patients on peritoneal dialysis

AIM

The aim of this study is to determine whether peritoneal membrane transport status (MTS) is associated with peritonitis or poor peritoneal dialysis-related outcomes.

METHODS

This retrospective cohort study analysed data of incident adult patients on peritoneal dialysis in Western Sydney between 1 October 2003 and 31 December 2012. Only patients who underwent peritoneal equilibration and adequacy tests within 6 months of commencement were included. Kaplan-Meier survival curves for time until first peritonitis and time until composite endpoint of peritonitis, death or technique failure, censored for transplant, were constructed.

RESULTS

About 397 patients, mean age 58.8(+/-2SD29) years, body mass index (BMI) 26.6(+/-5) kg/m² and serum albumin 35.4(+/-5) g/L were included. About 59.2% had high/high-average peritoneal MTS; 45.8% were past and current smokers; 51.9% developed at least one episode of peritonitis; 7.6% changed to haemodialysis; 6.3% underwent transplantation; 8.8% died; and 25.4% remained free of the aforementioned events over a mean follow-up period of 22.5 months (range 0-115 months). Peritoneal MTS was not associated with time to first peritonitis (p = 0.67) or composite endpoint of peritonitis, death or technique failure (p = 0.12). Smoking and hypoalbuminaemia independently predicted time to first peritonitis. Past and current smokers had a hazard ratio of 1.38 (95% CI 1.03-1.86) for shorter time to first peritonitis, significant after adjustment for serum albumin (p = 0.033). Serum albumin <32 g/L had a hazard ratio of 1.74 (95% CI 1.13-2.67) for shorter time to first peritonitis, significant after adjusting for smoking (p = 0.012).

CONCLUSION

Smoking and hypoalbuminaemia, but not MTS, were associated with shorter time to first peritonitis and composite endpoint of peritonitis, death and technique failure.

What PD Research in China Tells Us

Peritoneal dialysis (PD) was introduced in China later than in most Western countries, and PD research activity was quite limited until the 1990s. However, in the 2000s, and even more so during the last decade, there has been an unsurpassed increase in the number of PD patients, paralleled by a substantial increase in PD research activity reflected by an increasing number of PD papers from China. In this brief review, we describe some of the factors that may explain the dramatic developments in PD research in mainland China, such as the focus on basic research using scientific approaches that subsequently could be applied also in clinical studies. Another important factor was the growing interactions with international PD research centers in Hong Kong and in Western countries. Thanks to strong support from Chinese national and regional funding sources, a growing number of young Chinese researchers went to key international PD centers to learn about novel advanced research techniques. This paved the way for long-lasting, productive collaborations with benefits also for the foreign host institutions. Finally, we present some current research projects, including basic research that may contribute to the understanding of mechanisms behind complications such as peritonitis, and clinical projects aiming at improving PD management guidelines and better understanding of the potential of PD in China. Because of the size of the PD population, now the largest in the world, and the increasing number, and quality, of researchers in the PD field, PD research in China is destined to be a major contributor to advancements in PD in the near future.

Does Peritoneal Protein Transport Increase with Peritoneal Dialysis Therapy Duration and Lead to Extracellular Water Overload in Peritoneal Dialysis Patients?

Faster peritoneal transport status has been associated with adverse outcomes for peritoneal dialysis (PD) patients. Peritoneal protein clearance, through large pores, may be a surrogate marker of local inflammation. We wished to determine whether peritoneal protein transport increased with PD duration or was associated with extracellular water (ECW) expansion. We studied the relationships between 4 h Dialysate (D)/Serum (S) protein and ECW excess, using multifrequency bioelectrical impedance assessments, in 103 PD patients with up to 4 years of prospectively collected peritoneal equilibrium test (PET) results. 4 h PET D/S total protein and creatinine ratios were stable over time (K-W test, P = 0.063 and P = 0.3357, respectively). The initial PET 4 h D/S creatinine and D/S total protein correlated with ECW excess (r = 0.33, P = 0.003, and r = 0.27, P = 0.019, respectively), but thereafter there was no association. CRP and albumin did not correlate with 4 h D/S creatinine or total protein. Serial 4 h D/S total protein and 4 h D/S creatinine correlated all time points (P < 0.001). At the start of PD therapy, over-hydration (ECW excess) was observed with higher 4 h D/S creatinine and 4 h D/S total protein ratios, suggesting initial exposure to PD fluids causes faster transport. Thereafter changes in peritoneal creatinine and total protein transport mirrored each other suggesting that similar factors lead to changes in both small and large pore transport, and there was no sustained increase in larger pore transport with therapy time.

Influence of peritoneal transport characteristics on nutritional status and clinical outcome in Chinese diabetic nephropathy patients on peritoneal dialysis

Background:

High peritoneal transport status was previously thought to be a poor prognostic factor in peritoneal dialysis (PD) patients. However, its effect on diabetic nephropathy PD patients is unclear in consideration of the adverse impact of diabetes itself. The purpose of this study was to investigate the influence of peritoneal transport characteristics on nutritional status and clinical outcome in diabetic nephropathy patients on PD.

Methods:

One hundred and two diabetic nephropathy patients on PD were enrolled in this observational cohort study. According to the initial peritoneal equilibration test result, patients were divided into two groups: Higher transport group (HT, including high and high average transport) and lower transport group (LT, including low and low-average transport). Demographic characteristics, biochemical data, dialysis adequacy, and nutritional status were evaluated. Clinical outcomes were compared. Risk factors for death-censored technique failure and mortality were analyzed.

Results:

Compared with LT group (n = 37), serum albumin was significantly lower and the incidence of malnutrition by subjective global assessment was significantly higher in HT group (n = 65) (P < 0.05). Kaplan–Meier analyses showed that death-censored technique failure and mortality were significantly increased in HT group compared with that in LT group. On multivariate Cox analyses, higher peritoneal transport status and lower residual renal function (RRF) were independent predictors of death-censored technique failure when adjusted for serum albumin and total weekly urea clearance (Kt/V). Independent predictors of mortality were advanced age, anemia, hypoalbuminemia, and lower RRF, but not higher peritoneal transport status.

Conclusions:

Higher peritoneal transport status has an adverse influence on nutrition for diabetic nephropathy patients on PD. Higher peritoneal transport status is a significant independent risk factor for death-censored technique failure, but not for mortality in diabetic nephropathy patients on PD.

Increased peritoneal permeability at peritoneal dialysis initiation is a potential cardiovascular risk in patients using biocompatible peritoneal dialysis solution

Background

Cardiovascular disease is a frequent cause of death in peritoneal dialysis patients. Biocompatible peritoneal dialysis solutions with neutral pH have been anticipated to reduce cardiovascular disease more than conventional peritoneal dialysis solutions with low pH, but it remains unclear which factors at peritoneal dialysis initiation increase cardiovascular risk in patients using biocompatible peritoneal dialysis solutions. This study was undertaken to investigate which clinical factors at peritoneal dialysis initiation, including peritoneal transport status, are associated with cardiovascular event in patients using biocompatible peritoneal dialysis solution.

Methods

This retrospective cohort study of peritoneal dialysis patients using biocompatible solutions with neutral pH assessed relations of clinical parameters at peritoneal dialysis initiation to cardiovascular event during the subsequent five years.

Results

Of 102 patients who started peritoneal dialysis, cardiovascular event occurred in 18. Age, history of cardiovascular disease before peritoneal dialysis initiation, hemoglobin, serum albumin, C-reactive protein, peritoneal permeability defined by the ratio of dialysate to plasma creatinine concentration at 4 hr (D/Pcre) in peritoneal equilibration test (PET), number of patients in each PET category defined by D/Pcre, and peritoneal protein clearance significantly differed between patients with and without cardiovascular event. For patients divided according to PET category using Kaplan–Meier method, the group of high average to high peritoneal transporters exhibited significantly high incidence of cardiovascular event and mortality compared with the groups of low and low-average peritoneal transporters (Log rank; p = 0.0003 and 0.005, respectively). A Cox proportional hazards model showed independent association of PET category classification with cardiovascular event.

Conclusions

Peritoneal permeability expressed as PET category at peritoneal dialysis initiation is an independent cardiovascular risk factor in peritoneal dialysis patients using biocompatible peritoneal dialysis solution with neutral pH. Greater peritoneal permeability at peritoneal dialysis initiation might reflect subclinical vascular disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2369-15-173) contains supplementary material, which is available to authorized users.

High peritoneal transport status was not associated with mortality in peritoneal dialysis patients with diabetes

BACKGROUND

Continuous ambulatory peritoneal dialysis (CAPD) patients with diabetes are at increased risk of mortality and high peritoneal transporters appear to contribute to poor survival. However, little is known about the combined impacts of high peritoneal transporters and diabetes on mortality.

METHODS

This was a prospective observational cohort study. 776 incident CAPD patients were enrolled. Unadjusted and adjusted Cox proportional regression models were used to evaluate the association and interaction of peritoneal transport and diabetic status with mortality.

RESULTS

In the entire cohort, high peritoneal transport status was associated with an increased risk of all-cause mortality in unadjusted model [hazard ratio (HR) 2.35, 95% confidence interval (CI) 1.30 to 4.25, P = 0.01], but this association was not significant in multivariable model. There was an interaction between peritoneal membrane transport status and diabetes (P = 0.028). Subgroup analyses showed that compared to low and low average transporters, high transporters was associated with a higher risk of all-cause mortality (adjusted HR 1.78, 95% CI 1.07 to 4.70, P = 0.04) in CAPD patients without diabetes, but not in those with diabetes (adjusted HR 0.79, 95%CI 0.33 to 1.89, P = 0.59). Results were similar when transport status was assessed as a continuous variable.

CONCLUSIONS

The association between high peritoneal transport and all-cause mortality was likely to vary with diabetes status. High peritoneal transport was associated with an elevated risk of death among CAPD patients without diabetes, but not in those with diabetes.

Relative survival of peritoneal dialysis and haemodialysis patients: effect of cohort and mode of dialysis initiation

INTRODUCTION

Epidemiological studies consistently show an initial survival advantage for PD patients compared to HD. It has recently been suggested that this is due to the fact that many HD patients are referred late, and start dialysis on an acute, in-patient basis. The present study was performed to investigate (1) whether, and if so, how, PD and HD prognosis had changed in recent years, (2) whether a potential survival advantage of PD versus HD is constant over dialysis duration, and (3) whether differences in prognosis could be explained by patient age, renal diagnosis of diabetic nephropathy, or mode of dialysis initiation.

PATIENTS AND METHODS

12095 patients starting dialysis therapy between 1990 and 2010 in Denmark were studied. Prognosis was assessed according to initial dialysis modality on an intention-to-treat basis, censored for transplantation. Results were adjusted for age, sex, renal diagnosis, Charlson Comorbidity Index (CCI), and mode of dialysis initiation.

RESULTS

Overall adjusted prognosis improved by 34% (HD 30%, PD 42%). PD prognosis relative to HD improved, and was 16% better at the end of the period. Final PD prognosis improved consistently from 1990-99 to 2000-10 in all subgroups. PD was associated with a significant initial survival advantage, both overall and for all subgroups For the latter cohort, overall PD prognosis was better than HD for the first 4 years, after which it was insignificantly worse. The initial survival advantage was also present in a subgroup analysis of patients with early & routine ESRD initiation.

CONCLUSIONS

Dialysis survival has increased during the past 20 years. PD survival since 2000 has been better than HD, overall and for all subgroups. The difference in survival is not explained by mode of dialysis initiation.

Automated peritoneal dialysis in Hong Kong: there are two distinct groups of patients

AIM

To compare the clinical outcome between continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD) in specific subgroups of patients.

METHODS

We reviewed the clinical outcome of 90 consecutive incident APD patients and 180 CAPD patients in our centre.

RESULTS

The median follow up was 21.9 months (inter-quartile range, 9.5 to 46.5 months). The APD group was younger and had a lower Charlson's score than the CAPD group. Furthermore, the APD group had a highly skewed distribution of the Charlson's score, indicating the possibility of two different groups of patients. Multivariate analysis showed that in addition to the treatment mode (APD vs CAPD) and Charlson's score, there was a significant interaction between the two (P = 0.043) on patient survival. For patients with Charlson's score ≤6, the APD group had a significantly better patient survival than the CAPD group (78.3% vs. 65.4% at 5 years, P = 0.039), while for patients with Charlson's score ≥7, the APD group had a worse patient survival than the CAPD group (16.3% vs. 48.4% at 5 years, P = 0.028). Similarly, Charlson's score and its interaction with treatment mode, but not the APD group per se, were independent predictors of technique survival (P = 0.013). For patients with Charlson's score ≥7, the APD group had a significantly lower technique survival than the CAPD group (8.8% vs. 34.3%, P = 0.001), while for patients with Charlson's score ≤6, the technique survival was similar (44.4% vs. 42.5%, P = 0.15). Peritonitis-free survival was 35.2% and 32.2% for APD and CAPD groups, respectively (P = 0.021), and the difference was not affected by Charlson's score.

CONCLUSIONS

Comorbid diseases had a significant interaction with the mode of PD on patient and technique survival of incident PD patients. Our result suggests that APD may offer benefit in, and only in, young patients with minimal comorbid diseases.

Independent effects of systemic and peritoneal inflammation on peritoneal dialysis survival

Systemic inflammation, as evidenced by elevated inflammatory cytokines, is a feature of advanced renal failure and predicts worse survival. Dialysate IL-6 concentrations associate with variability in peritoneal small solute transport rate (PSTR), which has also been linked to patient survival. Here, we determined the link between systemic and intraperitoneal inflammation with regards to peritoneal membrane function and patient survival as part of the Global Fluid Study, a multinational, multicenter, prospective, combined incident and prevalent cohort study (n=959 patients) with up to 8 years of follow-up. Data collected included patient demographic characteristics, comorbidity, modality, dialysis prescription, and peritoneal membrane function. Dialysate and plasma cytokines were measured by electrochemiluminescence. A total of 426 survival endpoints occurred in 559 incident and 358 prevalent patients from 10 centers in Korea, Canada, and the United Kingdom. On patient entry to the study, systemic and intraperitoneal cytokine networks were dissociated, with evidence of local cytokine production within the peritoneum. After adjustment for multiple covariates, systemic inflammation was associated with age and comorbidity and independently predicted patient survival in both incident and prevalent cohorts. In contrast, intraperitoneal inflammation was the most important determinant of PSTR but did not affect survival. In prevalent patients, the relationship between local inflammation and membrane function persisted but did not account for an increased mortality associated with faster PSTR. These data suggest that systemic and local intraperitoneal inflammation reflect distinct processes and consequences in patients treated with peritoneal dialysis, so their prevention may require different therapeutic approaches; the significance of intraperitoneal inflammation requires further elucidation.

The influence of initial peritoneal transport characteristics, inflammation, and high glucose exposure on prognosis for peritoneal membrane function

BACKGROUND

Fast transport status, acquired with time on peritoneal dialysis (PD), is a pathology induced by peritoneal exposure to bioincompatible solutions. Fast transport has important clinical consequences and should be prevented.

OBJECTIVE

We analyzed the repercussions of initial peritoneal transport characteristics on the prognosis for peritoneal membrane function, and also whether the influence of peritonitis and high exposure to glucose are different according to the initial peritoneal transport characteristics or the moment when such events occur.

METHODS

The study included 275 peritoneal dialysis patients with at least 2 peritoneal function studies (at baseline and 1 year). Peritoneal kinetic studies were performed at baseline and annually. Those studies consist of a 4-hour dwell with glucose (1.5% during 1981 - 1990, and 2.27% during 1991 - 2002) to calculate the peritoneal mass transfer coefficients of urea and creatinine (milliliters per minute) using a previously described mathematical model.

RESULTS

Membrane prognosis and technique survival were independent of baseline transport characteristics. Fast transport and ultrafiltration (UF) failure are reversible conditions, provided that peritonitis and high glucose exposure are avoided during the early dialysis period. The first year on PD is a main determining factor for the membrane's future, and the mass transfer coefficient of creatinine at year 1 is the best functional predictor of future PD history. After 5 years on dialysis, permeability frequently increases, and UF decreases. Icodextrin is associated with peritoneal protection.

CONCLUSIONS

Peritoneal membrane prognosis is independent of baseline transport characteristics. Intrinsic fast transport and low UF are reversible conditions when peritonitis and high glucose exposure are avoided during the early dialysis period. Icodextrin helps in glucose avoidance and is associated with peritoneal protection.

Low-protein diet supplemented with keto acids is associated with suppression of small-solute peritoneal transport rate in peritoneal dialysis patients

Objective. We investigate whether low-protein diet would show benefits in suppressing peritoneal transport rate in peritoneal dialysis (PD) patients. Methods. This is a supplemented analysis of our previously published trial, which randomized 60 PD patients to receive low- (LP: dietary protein intake of 0.6–0.8 g/kg/d), keto-acid-supplemented low- (sLP: 0.6–0.8 g/kg/d with 0.12 g/kg/d of keto acids), or high- (HP: 1.0–1.2 g/kg/d) protein diet and lasted for one year. In this study, the variations of peritoneal transport rate were assessed. Results. While baseline D/P_cr (dialysate-to-plasma concentration ratio for creatinine at 4 hour) and D/D0_glu (dialysate glucose at 4 hour to baseline dialysate glucose concentration ratio) were similar, D/P_cr in group sLP was lower, and D/D0_glu was higher than those in the other two groups (P < 0.05) at 12th month. D/D0_glu increased (P < 0.05), and D/P_cr tended to decrease, (P = 0.071) in group sLP. Conclusions. Low-protein diet with keto acids may benefit PD patients by maintaining peritoneum at a lower transport rate.

Initial high peritoneal transport status is not a predictor of mortality in peritoneal dialysis patients

OBJECTIVE

Initial high peritoneal permeability in peritoneal dialysis (PD) patients was previously thought to be a poor prognostic factor. We aimed to study the factors that determine the initial transport status and prognosis in PD patients.

METHODS

This was an observation cohort study that enrolled 551 fresh uremic patients who commenced PD in a single PD center from January 1994 to December 2004. Patients with different initial peritoneal transport status were analyzed and determinants of the initial peritoneal transport status were evaluated. All patients were followed up to investigate the risks of mortality.

RESULTS

At the start of PD, only age and sex were determinants of the initial peritoneal transport status upon multiple linear regression analysis. The average duration of the study follow-up was 45.4 +/- 29.4 months. In the follow-up, a regression toward mean of transport status was found. About 107 patients died during the observation period. Cox-multivariate analysis revealed only age (RR = 1.06, p < 0.001), comorbidity index (RR = 2.31, p < 0.001), serum albumin (RR = 0.58, p = 0.008), and percentage of lean body mass (RR = 0.97, p = 0.008) to be independent predictors of mortality.

CONCLUSION

We observed that the initial peritoneal transport status is not a determinant factor of long-term mortality. The reason may be due to a consequence of regression toward mean of the transport status. Whether the observed longitudinal regression-to-mean phenomenon change represent any physiologic relevance is hard to define. Further studies on the underlying mechanisms are needed.

Peritoneal albumin and protein losses do not predict outcome in peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

Peritoneal clearance of albumin-unlike the transport of small molecules-is defined by both vascular surface area and size-selective permeability. Few studies have supported a positive correlation between peritoneal albumin loss and mortality. The aim of this study was to investigate whether baseline peritoneal loss and clearance of albumin and other proteins is a risk factor of death in peritoneal dialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

All incident peritoneal dialysis patients in our center during the last 15 years were included. Mass-transfer area coefficient of creatinine and peritoneal clearances of albumin, β₂-microglobulin, α₂-macroglobulin, and immunoglobulin G were calculated during a standard peritoneal permeability analysis. The total amount of albumin loss in the dialysate was also calculated. Overall mortality was studied with an intention-to-treat analysis.

RESULTS

Two hundred fifty-seven patients were included. High baseline albumin clearance was associated with fast transport status, the presence of peripheral arterial disease, and a high comorbidity index, whereas C-reactive protein levels did not differ from the patients with low albumin clearance. Age, high comorbidity score, C-reactive protein levels >10 mg/L, and a low serum albumin were associated with mortality. Peritoneal albumin clearances and albumin loss were not associated with death in crude and adjusted analysis. Similarly, peritoneal clearances of immunoglobulin G, α₂-macroglobulin, and β₂-microglobulin were not determinants of survival.

CONCLUSIONS

Baseline peritoneal albumin and protein clearances are associated with signs of comorbidity, but this does not have a measurable effect on patient survival.

High peritoneal transport status is not an independent risk factor for high mortality in patients treated with automated peritoneal dialysis

We undertook this study to elucidate whether baseline peritoneal membrane transport characteristics are associated with high mortality in incident automated peritoneal dialysis (APD) patients. This retrospective study includes 117 patients who started APD at Yonsei University Health System from 1996 to 2008 and had a PET within 3 months of APD initiation. High transporters were significantly older and had a higher incidence of cardiovascular disease. Patient survival for years 1, 3, and 5 were 85%, 64%, and 35% for high transporter and 94%, 81%, and 68% for non-high transporter group (P<0.01). Multivariate analysis revealed that age, diabetes, cardiovascular disease, serum albumin level, and residual renal function were independently associated with high mortality in APD patients. In contrast, high transport status was not a significant predictor for mortality in this population when the other covariates were included. Even though high transport was significantly associated with mortality in the univariate analysis, its role seemed to be influenced by other comorbid conditions. These findings suggest that the proper management of these comorbid conditions, as well as appropriate ultrafiltration by use of APD and/or icodextrin, must be considered as protective strategies to improve survival in peritoneal dialysis patients with high transport.

Plasma volume, albumin, and fluid status in peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

Peritoneal dialysis (PD) patients may be overhydrated especially when inflammation is present. We hypothesized that patients with a plasma albumin below the median value would have measurable overhydration without a proportional increase in plasma volume (PV).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We investigated a cross-sectional sample of 46 prevalent PD patients powered to detect a proportional increase in PV associated with whole body overhydration and hypoalbuminemia. PV was determined from (125)I-labeled albumin dilution, absolute total body water from D dilution (TBW(D)), and relative hydration from multifrequency bioimpedance analysis (BIA; Xitron 4200) expressed as the extracellular water (ECW):TBW(BIA) ratio.

RESULTS

Whereas patients with plasma albumin below the median (31.4 g/dl) were overhydrated as determined both by BIA alone (ECW:TBW(BIA) 0.49 versus 0.47, P < 0.036) and the difference between estimated TBW(BIA) and measured TBW(D) (3.55 versus 0.94 L, P = 0.012), corrected PV was not different (1463 versus 1482 ml/m(2), NS). Mean PV was not different from predicted, and its variance did not correlate with any other clinical measures. Multivariate analysis showed that the only independent predictor of whole body overhydration was reduced plasma albumin.

CONCLUSIONS

Hypoalbuminemia is an important determinant of tissue overhydration in PD patients. This overhydration is not associated with an increased plasma volume. Attempts to normalize the ECW:TBW ratio in hypoalbuminemic, inflamed PD patients may lead to hypovolemia and loss of residual renal function.

Superior survival of high transporters treated with automated versus continuous ambulatory peritoneal dialysis

BACKGROUND

Automated peritoneal dialysis (APD) is widely recommended for the management of high transporters by the International Society of Peritoneal Dialysis (ISPD), although there have been no adequate studies to date comparing the outcomes of APD and continuous ambulatory peritoneal dialysis (CAPD) in this high risk group.

METHODS

The relative impact of APD versus CAPD on patient and technique survival rates was examined by both intention-to-treat (PD modality at Day 90) and 'as-treated' time-varying Cox proportional hazards model analyses in all patients who started PD in Australia or New Zealand between 1 April 1999 and 31 March 2004 and who had baseline peritoneal equilibration tests confirming the presence of high peritoneal transport status.

RESULTS

During the study period, 4128 patients commenced PD. Of these, 628 patients were high transporters on PD at Day 90 (486 on APD and 142 on CAPD). Compared to high transporters treated with CAPD, APD-treated high transporters were more likely to be younger and Caucasian, and less likely to be diabetic. On multivariate intention-to-treat analysis, APD treatment was associated with superior survival [adjusted hazard ratio (HR) 0.56, 95% confidence interval (CI) 0.35-0.87] and comparable death-censored technique survival (HR 0.88, 95% CI 0.64-1.21). Superior survival of high transporters treated with APD versus CAPD was also confirmed in supplemental as-treated analysis (HR 0.72, 95% CI 0.54-0.96), matched case-control analysis (HR 0.60, 95% CI 0.36-0.96) and subgroup analysis of high transporters treated entirely with APD versus those treated entirely with CAPD (HR 0.29, 95% CI 0.14-0.60). There were no statistically significant differences in patient survival or death-censored technique survival between APD and CAPD for any other transport group, except for low transporters, who experienced a higher mortality rate on APD compared with CAPD (HR 2.19, 95% CI 1.02-4.70).

CONCLUSIONS

APD treatment is associated with a significant survival advantage in high transporters compared with CAPD. However, APD treatment is associated with inferior survival in low transporters.

Effects of Twice-Daily Icodextrin Administration on Blood Pressure and Left Ventricular Mass in Patients on Continuous Ambulatory Peritoneal Dialysis

Background

Hypervolemia is a risk factor for left ventricular hypertrophy and hypertension in peritoneal dialysis patients. Icodextrin improves volume control by increasing ultrafiltration in peritoneal dialysis patients.

Aim

To examine the effects of twice-daily icodextrin administration on blood pressure and left ventricular hypertrophy in peritoneal dialysis patients with hypervolemia and ultrafiltration failure.

Method and Results

Administration of icodextrin twice daily resulted in a significant reduction in the left ventricular mass index (LVMI) of patients by the end of the third month ( p < 0.05). The reduction in LVMI was also significant for the once-daily icodextrin group ( p < 0.05). Mean blood pressure of patients receiving icodextrin twice daily was significantly reduced ( p < 0.05). By the end of the third month no significant changes were observed in mean blood pressure of the patients using once-daily icodextrin ( p > 0.05). No statistically significant changes were observed in weekly total creatinine clearances or Kt/V of patients in either group at the end of 3 months (NS).

Conclusion

Twice-daily icodextrin administration was clinically beneficial as shown by reduced blood pressure and prevention of the progress of left ventricular hypertrophy without causing any decrease in dialysis adequacy or any side effects. The icodextrin metabolite results did not suggest any further increase in their values when comparing once- to twice-daily administration of icodextrin. Although prescription of icodextrin once daily may yield good clinical results in the long term, this study showed that it may be more efficient to use twice-daily icodextrin for at least a specific period for the purpose of obtaining quicker results in patients with ultrafiltration failure, serious hypervolemia, or hard-to-control blood pressure conditions.

Peritoneal protein clearance and not peritoneal membrane transport status predicts survival in a contemporary cohort of peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

Fast peritoneal membrane transport status may be due to inflammation or increased peritoneal membrane surface area. We evaluated the ability of peritoneal protein clearance (Pcl) to distinguish fast peritoneal membrane transport status as a consequence of peritoneal membrane inflammation and assess its impact on patient survival.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients who initiated peritoneal dialysis at our center since January 1998 and had a baseline peritoneal equilibration test, measurement of dialysis adequacy, and 24-h dialysate Pcl were included. Demography, comorbidities, and biochemical data were prospectively collected. Follow-up was until death or the end of the period studied. Multivariate regression analysis identified factors that were associated with Pcl. A Cox proportional hazards model was used to identify factors that were associated with survival.

RESULTS

A total of 192 patients (56% men, mean age 54.3 +/- 15.3; 32% with diabetes) were included. On univariate analysis, Pcl was negatively correlated with serum albumin and positively correlated with age, dialysate/plasma creatinine ratio (D/Pcr), the presence of peripheral vascular disease, and urine volume. On multivariate analysis, serum albumin, D/Pcr, urine volume, and peripheral vascular disease remained significant. Predictors of mortality were age, comorbidity grade, and Pcl but not D/Pcr.

CONCLUSIONS

In this cohort, peritoneal transport status no longer predicted survival, whereas Pcl remained a predictor. Increased large-pore protein loss may reflect the severity of underlying cardiovascular disease, portending a poor prognosis for these patients.

A Strict Low Protein Diet during the Predialysis Period Suppresses Peritoneal Permeability at Induction of Peritoneal Dialysis

Background

The factors that predict baseline peritoneal permeability remain largely unknown. We noticed that patients that adhered to a strict low protein diet (LPD) during the predialysis period seldom showed high peritoneal permeability on the peritoneal equilibration test (PET) at the introduction of peritoneal dialysis (PD). Therefore, we investigated whether a strict LPD during the predialysis period affects peritoneal permeability.

Method

We retrospectively analyzed 37 patients that started PD in a single Japanese center. Patients were divided into group A and group B by the median amount of daily protein intake (PI) during the predialysis period using urine collected over 24 hours.

Results

There were no differences between groups A and B in age, gender, proportion of diabetic nephropathy, blood pressure, body mass index, or body surface area. There were also no differences between the groups in laboratory findings, including hematocrit, serum albumin, and serum creatinine. The PETs showed a significantly lower dialysate-to-plasma ratio of creatinine at 4 hours (Cr D/P) for group A than for group B ( p = 0.02). Furthermore, a significant positive correlation between Cr D/P and PI was observed ( r = 0.53, p < 0.01).

Conclusion

It is suggested that a strict LPD during the predialysis period may suppress peritoneal permeability at induction of PD.

Association of Peritoneal Dialysis Clinic Size with Clinical Outcomes

Objective

Very few studies have addressed the relationship between number of peritoneal dialysis (PD) patients treated at a clinic (PD clinic size) and clinical outcomes. In a national prospective cohort study of incident PD patients ( n = 236, from 26 clinics), we examined whether being treated at a larger PD clinic [>50 PD patients ( n = 3 clinics) vs <50 PD patients ( n = 23 clinics)] was associated with better patient outcomes, including fewer switches to hemodialysis, fewer cardiovascular events, lower cardiovascular mortality, and lower all-cause mortality.

Methods

Multivariable Cox models were used to assess relative hazards (RHs) for modality switches, cardiovascular events, cardiovascular deaths, and all-cause deaths by PD clinic size. All models were adjusted for demographics, comorbidities, laboratory values, and clinic years in operation.

Results

Being treated at a clinic with >50 patients was associated with fewer switches to hemodialysis (RH = 0.13, 95% CI 0.06 – 0.31) and fewer cardiovascular events (RH = 0.62, 95% CI 0.06 – 0.98). No associations of PD clinic size with cardiovascular or all-cause mortality were seen.

Conclusion

PD patients treated at clinics with greater numbers of PD patients may have better outcomes in terms of technique failure and cardiovascular morbidity. PD clinic size may act as a proxy of greater PD experience, more focus on the modality, and better PD practices at the clinic, resulting in better outcomes.

Patient Selection for Automated Peritoneal Dialysis: For Whom, When?

The use of the various forms of automated peritoneal dialysis (APD) has increased considerably in the past few years. This increase has in part been driven by technology, through improved cycler design. Other contributing factors include better adjustment of APD to patient lifestyle, the flexibility that APD offers to patients, and the increased ability of APD to achieve adequacy and ultrafiltration targets. For high transporters and for patients unable to perform peritoneal dialysis (PD) on their own (for example, pediatric and elderly patients), APD is considered the most suitable PD modality. Furthermore, APD has been associated with improved compliance, lower intraperitoneal pressure, and lower incidences of peritonitis. On the other hand, concerns have been raised regarding increased complexity and cost, a more rapid decline in residual renal function, inadequate sodium removal, and disturbed sleep. Automated PD is an alternative to continuous ambulatory PD when a higher dialysis dose is needed, and it could be a reliable alternative for unplanned or urgent dialysis start. Other than beneficial results in high transporters, the medical advantages of APD remain controversial. Individual patient choice therefore remains the main indication for the application of APD, which should be made available to all patients starting PD.

Peritoneal membrane structural and functional changes during peritoneal dialysis

Peritoneal dialysis is now utilized as a renal replacement therapy modality in a substantial percentage of patients with end-stage renal disease, with excellent short-term patient and technique survival rates. However, the potential complications associated with longer-term therapy, such as ultrafiltration failure or encapsulating peritoneal sclerosis, have led to raise some concern about peritoneal dialysis as an adequate mode of treatment of end-stage renal disease in the long term. In the last decade, a substantial amount of information has been gathered on the characteristics of the peritoneal membrane at the onset of peritoneal dialysis, and on the anatomical and pathophysiologic changes that occur with long-term peritoneal dialysis. I will review this subject with a special focus on the various strategies that can help protect the peritoneal membrane during peritoneal dialysis so as to allow peritoneal dialysis to succeed as a long-term dialysis modality.