Preservation of residual renal function and factors affecting its decline in patients on peritoneal dialysis

The relationship between decline rate of residual renal function in the first year and mortality in peritoneal dialysis patients

INTRODUCTION

To assess the relationship between the rate of residual renal function (RRF) decline in the first year and all-cause and cardiovascular mortality in peritoneal dialysis (PD) patients.

METHODS

Incident PD patients were divided into two groups by the corresponding RRF decline value, when hazard ratio (HR) = 1 was found by the restricted cubic spline. The associations of rate of decline of RRF in the first year with mortality were evaluated.

RESULTS

Of 497 PD patients, 122 patients died. After adjusting for confounding factors, patients in fast-decline group had a significant increase risk of all-cause and cardiovascular mortality (HR: 1.97 and 2.09, respectively). Each 0.1-mL/min/1.73 m2 /month decrease in RRF in the first year of PD was associated with a 19% and 20% higher risk of all-cause and cardiovascular mortality, respectively.

CONCLUSIONS

Faster decline of RRF in the first year was independently associated with all-cause and cardiovascular mortality in PD patients.

On the importance of the interplay of residual renal function with clinical outcomes in end-stage kidney disease

Chronic kidney disease (CKD) is one of the most important public health concerns of the century, and is associated with high rates of morbidity, mortality and social costs. CKD evolving towards end-stage kidney disease (ESKD) is on the rise resulting in a greater number of patients requiring peritoneal dialysis (PD) and hemodialysis (HD). The aim of this manuscript is to review the current literature on the interplay of residual renal function (RRF) with clinical outcomes in ESKD. The persistence of RRF is one of the most important predictors of decreased morbidity, mortality, and better quality of life in both PD and HD patients. RRF contributes to the well-being of ESKD patients through various mechanisms including higher clearance of solutes, maintenance of fluid balance, removal of uremic toxins and control of electrolytes. Furthermore, RRF has beneficial effects on inflammation, anemia, malnutrition, diabetes mellitus, obesity, changes in the microbiota, and cardiac diseases. Several strategies have been proposed to preserve RRF, such as blockade of the renin-angiotensin-aldosterone system, better blood pressure control, incremental PD and HD. Several clinical trials investigating the issue of preservation of RRF are ongoing. They are needed to broaden our understanding of the interplay of RRF with clinical outcomes in ESKD.

Association of Urinary Dickkopf-3 with Residual Renal Function Decline in Patients Undergoing Peritoneal Dialysis

Background and Objectives: Urinary levels of dickkopf-3 (DKK-3) are associated with poor renal survival in patients with non-dialytic chronic kidney disease. However, it remains unknown whether urinary DKK-3 levels can predict residual renal function (RRF) decline in patients undergoing peritoneal dialysis (PD). Therefore, we investigated the correlation between urinary levels of DKK-3 and the subsequent rate of RRF decline in PD patients. Materials and Methods: This study included 36 PD patients who underwent multiple peritoneal equivalent tests during 2011–2021. The relationship between baseline clinical characteristics and the subsequent annual rate of Kt/V decline was investigated. Results: The annual rate of renal Kt/V decline was 0.29 (range: 0.05–0.48), which correlated with renal Kt/V (r = 0.55, p = 0.0005) and 24 h urinary DKK-3 excretion (r = 0.61, p < 0.0001). Similarly, 24 h urinary DKK-3 excretion (β = 0.44, p = 0.0015) and renal Kt/V (β = 0.38, p = 0.0059) were independently associated with the annual rate of renal Kt/V decline in multivariate analyses. Conclusions: Urinary DKK-3 assessment may help identify PD patients at a high risk of RRF decline.

Effects of ACEIs and ARBs on the Residual Renal Function in Peritoneal Dialysis Patients: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

In peritoneal dialysis (PD) patients, whether angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) could protect residual renal function is still controversial. To assess the effects of ACEIs and ARBs on the residual renal function and cardiovascular (CV) events in peritoneal dialysis patients, we performed a meta-analysis of randomized controlled trials.

MATERIALS AND METHODS

We searched PubMed, EMBASE, the Cochrane Library, the CNKI database, and the Wanfang database for relevant articles from database inception to November 30, 2019. Randomized controlled trials were included. The primary outcome was the decline in the residual renal function (RRF).

RESULTS

Thirteen trials with 625 participants were included in the meta-analysis. The average residual GFR declined by 1.79 ml/min per 1.73 m² in the ACEI/ARB group versus 1.44 ml/min per 1.73 m² in the placebo or active control group at 3 mo. The average residual GFR declined by 2.02 versus 2.06, 2.16 versus 2.72, and -0.04 versus 2.74 ml/min per 1.73 m² in the placebo or active control group at 6 months (mo), 12 mo, and 24 mo, respectively. The decline in residual GFR showed a significant difference between the ACEI/ARB group and the placebo or active control group at 12 mo (MD = -0.64 ml/min per 1.73 m²; 95% CI: -0.97~-0.32; I ² = 44%; P < 0.0001). No significant difference was observed in Kt/V, urinary protein excretion, weekly creatinine clearance, CV events, or serum potassium levels.

CONCLUSIONS

In the present study, we found that the use of ACEIs and ARBs, especially long-term treatment, decreased the decline of RRF in patients on PD. ACEIs and ARBs do not cause an additional risk of side effects.

Continuous Ambulatory Peritoneal Dialysis is Better than Automated Peritoneal Dialysis as First-Line Treatment in Renal Replacement Therapy

This article examines the roles of continuous ambulatory peritoneal dialysis (CAPD) versus automated peritoneal dialysis (APD) as first-line renal replacement therapy. To date, no high-quality large-scale randomized controlled studies have compared CAPD with APD as first-line therapy. However, a discussion on this issue is important so that nephrologists can decide and patients can have a choice of modality on which to start dialysis, especially in the context of health care economics. We review the literature and present Hong Kong as the model of a “CAPD first” policy, an appealing, cost-effective approach for any country.

An ideal renal replacement therapy should provide optimal survival, lowest possible risk for comorbidity, highest level of quality of life, and equally important, acceptable cost to society. When we consider this subject in the context that all patients should be started on one first-line modality, the data suggest that a “CAPD first” policy has all these advantages, with APD probably having the edge only with regard to patient preference. The present review highlights preservation of residual renal function, removal and balancing of sodium, incidence of peritonitis, peritoneal membrane transport status, patient rehabilitation, and financial issues in demonstrating that a “CAPD first” policy is the model that should be adopted.

Automated Peritoneal Dialysis Has Significant Effects on Systemic Hemodynamics

Objectives

Maintenance of residual renal function (RRF) is an important determinant of outcome in peritoneal dialysis patients. It remains contentious as to whether automated peritoneal dialysis (APD) leads to an increased rate of decline of RRF compared with continuous ambulatory peritoneal dialysis (CAPD). We studied whether APD was associated with significant systemic hemodynamic changes that may play a role in the accelerated loss of RRF.

Methods

As a follow-on from a previous study, 8 well-established CAPD patients underwent a 4-hour APD treatment consisting of 3 drain/fill cycles using 2 x 2.5 L 1.36% glucose and 1 x 3.86% glucose dialysate. Each dwell phase lasted 76 minutes. Blood pressure (BP) and a full range of hemodynamic variables, including pulse (HR), stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR), were measured noninvasively using continuous arterial pulse wave analysis.

Results

BP fell during 2 of the 3 drain/fill periods when dialysate was drained from the peritoneal cavity, but then rose upon instillation of dialysate fluid. The fall in BP was associated with a fall in TPR, matched by an inadequate rise in SV and CO. Over the entire study period, TPR progressively rose to +53.4% above baseline ( p = 0.032). Both SV and CO fell over the same period, to -21.1% ( p = 0.060) and -22.4% from baseline ( p = 0.037) respectively. This did not result in any significant difference between start and end BP.

Conclusions

This study demonstrates that APD is associated with significant systemic hemodynamic effects. The increased number of drain/fill cycles compared to CAPD, or the progressive rise in TPR and reduction in CO (possibly due to a cooling effect), may potentially be factors that adversely affect RRF in APD patients.

Prescribing high-quality peritoneal dialysis: The role of preserving residual kidney function

Maintenance of residual kidney function (RKF) is independently associated with increased survival in patients with end-stage renal disease. Presence of RKF is also associated with improved volume status, better nutritional status, reduced erythropoietin requirement, and decreased rate of peritonitis in patients on peritoneal dialysis (PD). Thus, the preservation of RKF is an important therapeutic end point in the management of patients on PD. Measurement of RKF in PD patients should be based on the mean of 24-h urinary creatinine and urea clearances, and ideally, this should be done quarterly. Compared to those started on hemodialysis, patients initiated on PD appear to have slower decline in RKF. The choice of PD modality should be based on patient preference, as there is no clear evidence to date showing one modality is superior than the other in preserving RKF. Peritoneal dialysates with neutral pH and low glucose degradation products seem to have a favorable effect on RKF. An angiotensin-converting enzyme inhibitor or angiotensin receptor blocker should be used whenever possible to preserve RKF and reduce cardiac mortality. Both loop diuretics and icodextrin can be utilized to maintain fluid balance in PD patients. However, caution should be taken to avoid volume depletion which could accelerate RKF decline. Short-term use of aminoglycosides does not have a detrimental impact on RKF, but prolonged use (>3 weeks) should be avoided to minimize the risk of ototoxicity. Lastly, potential nephrotoxic agents such as intravenous contrast should be used judiciously.

The Effect of Automated versus Continuous Ambulatory Peritoneal Dialysis on Mortality Risk in China

Background

There is an emerging practice pattern of automated peritoneal dialysis (APD) in China. We report on outcomes compared to continuous ambulatory peritoneal dialysis (CAPD) in a Chinese cohort.

Methods

Data were sourced from the Baxter Healthcare (China) Investment Co. Ltd Patient Support Program database, comprising an inception cohort commencing PD between 1 January 2005 and 13 August 2015. We used time-dependent cause-specific Cox proportional hazards and Fine-Gray competing risks (kidney transplantation, change to hemodialysis) models to estimate relative mortality risk between APD and CAPD. We adjusted or matched for age, gender, employment, insurance, primary renal disease, size of PD program, and year of dialysis inception. We used cluster robust regression to account for center effect.

Results

We modeled 100,351 subjects from 1,178 centers over 240,803 patient-years. Of these, 368 received APD at some time. Compared with patients on CAPD, those on APD were significantly younger, more likely to be male, employed, self-paying, and from larger programs. Overall, APD was associated with a hazard ratio (HR) for death of 0.79 (95% confidence interval [CI] 0.64 – 0.97) compared with CAPD in Cox proportional hazards models, and 0.76 (0.62 – 0.95) in Fine-Gray competing risks regression models. There was prominent effect modification by follow-up time: benefit was observed only up to 4 years follow-up, after which risk of death was similar.

Conclusion

Automated peritoneal dialysis is associated with an overall lower adjusted risk of death compared with CAPD in China. Analyses are limited by the likelihood of important selection bias arising from group imbalance, and residual confounding from unavailability of important clinical covariates such as comorbidity and Kt/V.

Combination therapy of exendin-4 and allogenic adipose-derived mesenchymal stem cell preserved renal function in a chronic kidney disease and sepsis syndrome setting in rats

Combined therapy with exendin-4 (Ex4) and allogenic adipose-derived mesenchymal stem cells (ADMSC) was tested against either therapy alone for protecting kidney function against chronic kidney disease (CKD) complicated by sepsis syndrome (SS) [i.e., by intraperitoneal injection of cecal-derived bacteria (1.0 × 104) cells/milliliter/total 5.0 cc].Adult-male-Sprague Dawley rats (n=36) were equally divided into group 1 (sham-control), group 2 (CKD), group 3 (CKD-SS), group 4 (CKD-SS-Ex4), group 5 (CKD-SS-ADMSC) and group 6 (CKD-SS-Ex4-ADMSC). At day 42 after CKD induction SS was induced. Thirty-minutes after SS induction, ADMSCs (2.0 ×106 cells) were intravenously administered to groups 5 and 6. Ex4 (10 μg/kg) was intraperitoneally administered groups 4 and 6 at 30 min and days 1 to 5 after SS induction. Animals were euthanized at day 47 after CKD induction. Kidney-injury score, collagen-deposition area, and creatinine/BUN levels were lowest in group 1, highest in group 3 and significantly higher in group 2 than in groups 4 to 6 in a progressively increasing manner (all P<0.0001). Protein expressions of inflammatory (MMP-9/TNF-α/NF-κB/IL-1ß/ICAM-1), oxidative-stress (NOX-1/NOX-2/oxidized protein), apoptotic (mitochondrial-Bax/cleaved-caspase-3/cleaved-PARP) and fibrotic/DNA-damaged (Smad3/TGF-ß/γ-H2AX) biomarkers showed an identical pattern, whereas anti-fibrotic (BMP-2/Smad1/5), anti-apoptotic/endothelial-integrity (Bcl-2/eNOS) and podocyte-integrity (ZO-1/p-cadherin) biomarkers exhibited an opposite pattern of kidney-injury score among the six groups (all P>0.0001). Cellular expressions of inflammatory (CD14/CD68) and glomerulus/tubular-injury (WT-1/KIM-1) biomarkers displayed an identical pattern, whereas glomerulus/podocyte-component (dystroglycan/nephrin/ZO-1/fibronectin/p-cadherin) biomarkers showed an opposite kidney-injury score among the six groups (all P<0.0001). In conclusion, Ex4-ADMSC therapy effectively preserved renal function in the CKD-SS setting.

Comparison of Change in Peritoneal Function in Patients on Continuous Ambulatory PD vs Automated PD

Background

Patients on automated peritoneal dialysis (APD) may have greater exposure to glucose in the PD fluid than those on continuous ambulatory PD (CAPD). If this causes long-term damage to the peritoneal membrane, it will have implications for a patient's choice of modality.

Methods

Membrane function of long-term APD or CAPD patients was followed prospectively. The data were collected from electronic patient records in our unit from 2000 to 2014. The rate of change in membrane transport status (D/Pcr) and ultrafiltration (UF4) for each patient was calculated using the least square regression line equation.

Results

We identified 106 APD and 123 CAPD patients who had a mean of 8.4 peritoneal equilibration test (PET) over 5.6 years. No differences were found in the rate of changes in D/Pcr or UF4. Baseline solute clearance (Kt/V) was lower in APD patients (1.66 vs 1.76, p = 0.04). However, APD patients experienced incremental changes to dialysis prescription that resulted in a greater increase in Kt/V compared with CAPD patients.

Conclusion

This is the largest study comparing the long-term effect of APD vs CAPD prescriptions. Despite more glucose being prescribed, there were no differences in the evolution of peritoneal membrane transport characteristics. The lower baseline Kt/V of APD patients might be explained by our aggressive use of incremental APD (tidal with dry day). Despite greater glucose prescriptions, initiating patients on APD based on patient preference appears to be safe for the long-term integrity of the peritoneal membrane.

Predictors of Residual Renal Function Decline in Peritoneal Dialysis Patients: The balANZ Trial

Objective

Preservation of residual renal function (RRF) is associated with improved survival. The aim of the present study was to identify independent predictors of RRF and urine volume (UV) in incident peritoneal dialysis (PD) patients.

Methods

The study included incident PD patients who were balANZ trial participants. The primary and secondary outcomes were RRF and UV, respectively. Both outcomes were analyzed using mixed effects linear regression with demographic data in the first model and PD-related parameters included in a second model.

Results

The study included 161 patients (mean age 57.9 ± 14.1 years, 44% female, 33% diabetic, mean follow-up 19.5 ± 6.6 months). Residual renal function declined from 7.5 ± 2.9 mL/min/1.73 m2 at baseline to 3.3 ± 2.8 mL/min/1.73 m2 at 24 months. Better preservation of RRF was independently predicted by male gender, higher baseline RRF, higher time-varying systolic blood pressure (SBP), biocompatible (neutral pH, low glucose degradation product) PD solution, lower peritoneal ultrafiltration (UF) and lower dialysate glucose exposure. In particular, biocompatible solution resulted in 27% better RRF preservation. Each 1 L/day increase in UF was associated with 8% worse RRF preservation ( p = 0.007) and each 10 g/day increase in dialysate glucose exposure was associated with 4% worse RRF preservation ( p < 0.001). Residual renal function was not independently predicted by body mass index, diabetes mellitus, renin angiotensin system inhibitors, peritoneal solute transport rate, or PD modality. Similar results were observed for UV.

Conclusions

Common modifiable risk factors which were consistently associated with preserved RRF and residual UV were use of biocompatible PD solutions and achievement of higher SBP, lower peritoneal UF, and lower dialysate glucose exposure over time.

Risk Factors for Decline of Residual Renal Function in Children Treated With Peritoneal Dialysis

♦ BACKGROUND: The aim of the study was to assess risk factors for residual renal function (RRF) decline in children during the first/second year of chronic peritoneal dialysis (PD). ♦ METHODS: The study group included 56 children with end-stage renal disease (ESRD) (age 10.13 ± 4.86 years), including 18 on continuous ambulatory PD (CAPD) and 38 on automated PD (APD), in whom we evaluated RRF (daily diuresis [mL/m2/24 h], residual glomerular filtration rate (rGFR) [mL/min/1.73 m2]), etiology of ESRD, PD fluid volume (mL/m2/24 h), glucose load (g/m2/24 h), ultrafiltration (mL/m2/24 h), peritoneal permeability (D/PCrea 4h, D/D0 Glu 4h), dialysis adequacy (twKt/V, twCCr [L/week/1.73 m2]), blood pressure (BP), biochemical parameters, and medications used. Duration of follow-up was 24 months. ♦ RESULTS: Mean diuresis before initiation of PD was 1,394.93 ± 698.37 (mL/m2/24 h), and mean rGFR was 7.41 ± 3.96 (mL/min/1.73 m2). The rate of daily diuresis decline was -529.34 ± 546.28 in the first year and -107.10 ± 291.54 (mL/m2/24 h) in the second year (p = 0.005), and the rate of rGFR decline was -3.35 ± 3.73 in the first year and -1.63 ± 1.85 (mL/min/1.73 m2) in the second year (p = 0.118). Eleven (19.64%) patients became anuric. In univariate analysis, the rate of daily diuresis decline in the first year was related to baseline diuresis (r = -0.29, p = 0.031), proteinuria (r = -0.43, p = 0.001), and systolic BP (r = -0.31, p = 0.020); 12-month changes (Δ0 - 12) in PD fluid volume (r = -0.37, p = 0.004), glucose load (r = -0.28, p = 0.035), and ultrafiltration (r = -0.38, p = 0.004); serum calcium-phosphorus product (r = -0.41, p = 0.002); and Δ0 - 12 body mass index (BMI) Z-score (r = 0.30, p = 0.024); while the rate of rGFR decline in the first year was related only to baseline rGFR (r = -0.57, p < 0.001). In multivariate analysis, significant predictors of the rate of daily diuresis decline in the first year were baseline diuresis (β = -0.386, p < 0.001) and proteinuria (β = -0.278, p = 0.017), mean systolic BP Z-score (β = -0.237, p = 0.027), and age at the onset of PD (β = -0.224, p = 0.037), while predictors of the rate of rGFR decline were baseline rGFR (β = -0.607, p < 0.001) and baseline proteinuria (β = -0.225, p = 0.046). In the second year, the only predictors of the rate of rGFR decline were D/D0 Glu 4h (r = 0.44, p = 0.033, univariate analysis) and rGFR at 12 months (β = -0.499, p = 0.044). ♦ CONCLUSION: The most important risk factors for rapid RRF decline in children during the first year of chronic PD include higher baseline daily diuresis and proteinuria, and additional factors are systolic BP and age at the onset of PD; while high baseline GFR and low peritoneal transport status may be the only important factors during the second year.

Advances in Understanding and Management of Residual Renal Function in Patients with Chronic Kidney Disease

BACKGROUND

Residual renal function (RRF), defined as the ability of native kidneys to eliminate water and uremic toxins, is closely correlated with mortality and morbidity rates among patients receiving either peritoneal dialysis (PD) or hemodialysis (HD) via continuous clearance of middle-sized molecules and protein-bound solutes. Therefore, preserving RRF is considered to be one of the primary goals in managing patients with end-stage renal disease (ESRD).

SUMMARY AND KEY MESSAGES

In this article, we provide a review on the understanding and management of RRF in patients on dialysis. RRF may be estimated and measured by calculating the mean 24-hour urine creatinine level and urea clearance. Currently, several middle-sized molecules are reported but rarely used in practice. Many risk factors such as original renal diseases, dietary intake, and nephrotoxic agents impair RRF. Targeting such factors may halt the decline in RRF and offer better outcomes for patients on PD or HD. Except for in PD patients, RRF is a powerful predictor of survival in HD patients. RRF requires more clinical and research attention in the care of patients with ESRD on dialysis.

Rate of Decline of Residual Kidney Function Before and After the Start of Peritoneal Dialysis

♦

BACKGROUND

There is a paucity of information on whether peritoneal dialysis (PD) slows the decline of residual kidney function (RKF) compared to the natural slope of RKF decline prior to dialysis start. Our aim was to analyze the RKF decline before and after initiating PD, and to determine the principal factors affecting this decline during the PD period. ♦

METHODS

We determined individual glomerular filtration rates (GFR) for approximately 12 months before and after PD in 77 new PD patients in a large academic medical center (2008 - 2012). The GFR was estimated by the Modification of Diet in Renal Disease (MDRD) equation in the predialysis period and by averaging 24-hour urine creatinine and urea clearances in the PD period. The rate of RKF decline was calculated using unadjusted linear regression analysis. Wilcoxon signed rank test was used to compare RKF decline before and after PD initiation. Multivariate linear regression was used to identify independent risk factors for RKF decline in the PD phase. ♦

RESULTS

A significantly slower mean rate of RKF decline was observed in the PD period compared with the predialysis period (-0.21 ± 0.30 vs -0.59 ± 0.55 mL/min/1.73 m(2)/month, p < 0.01). Higher baseline RKF, higher serum phosphate, and older age were independently associated with faster decline of RKF (all p < 0.01). ♦

CONCLUSIONS

In patients with advanced chronic kidney disease, initiating PD was associated with a slower rate of RKF decline compared to the rate in the predialysis period.

Risk factors for loss of residual renal function in children treated with chronic peritoneal dialysis

In dialyzed patients, preservation of residual renal function is associated with better survival, lower morbidity, and greater quality of life. To analyze the evolution of residual diuresis over time, we prospectively monitored urine output in 401 pediatric patients in the global IPPN registry who commenced peritoneal dialysis (PD) with significant residual renal function. Associations of patient characteristics and time-variant covariates with daily urine output and the risk of developing oligoanuria (under 100 ml/m²/day) were analyzed by mixed linear modeling and Cox regression analysis including time-varying covariates. With an average loss of daily urine volume of 130 ml/m² per year, median time to oligoanuria was 48 months. Residual diuresis significantly subsided more rapidly in children with glomerulopathies, lower diuresis at start of PD, high ultrafiltration volume, and icodextrin use. Administration of diuretics significantly reduced oligoanuria risk, whereas the prescription of renin–angiotensin system antagonists significantly increased the risk oligoanuria. Urine output on PD was significantly associated in a negative manner with glomerulopathies (−584 ml/m²) and marginally with the use of icodextrin (−179 ml/m²) but positively associated with the use of biocompatible PD fluid (+111 ml/m²). Children in both Asia and North America had consistently lower urine output compared with those in Europe perhaps due to regional variances in therapy. Thus, in children undergoing PD, residual renal function depends strongly on the cause of underlying kidney disease and may be modifiable by diuretic therapy, peritoneal ultrafiltration, and choice of PD fluid.

Effect of hypertension and antihypertensive medications on residual renal function in children treated with chronic peritoneal dialysis

PURPOSE

To evaluate the effect of hypertension (HTN) and antihypertensive medications (AHM) on residual renal function (RRF) in children on CAPD and APD.

MATERIAL/METHODS

We retrospectively evaluated underlying kidney disease, systolic and diastolic blood pressure (SBP/DBP), presence and control of HTN (SBP/DBP≥95th percentile), AHM, RRF (daily diuresis, residual glomerular filtration rate [rGFR]), biochemical parameters, BMI Z-score, and dialysis parameters during 12-month follow-up in 87 children (38 CAPD, 49 APD) aged 10.22±4.31 years. The rate of RRF loss was expressed as absolute and relative [%] reduction.

RESULTS

At baseline, HTN was found in 74.7% patients (CAPD/APD: 84.2%/67.3%, P=0.06), most commonly in HUS and least frequently in CAKUT. The proportion of CAPD/APD patients with poorly controlled HTN was 70.0%/63.3% (P=0.50). Relative daily diuresis loss in children with uncontrolled HTN was higher (P=0.017) compared to children with SBP/DBP <95th percentile. No effect of AHM on the rate of RRF loss was found. In multivariate analysis, absolute daily diuresis loss was related to baseline diuresis (β=-0.30, P<0.001) and proteinuria (β=-0.31, P=0.004); absolute rGFR loss to baseline rGFR (β=-0.73, P<0.001) and glucose load after 12 months (β=-0.36, P=0.02); relative daily diuresis loss to mean BMI Z-score (β=-0.44, P=0.04); and relative rGFR to baseline rGFR (β=-0.37, P<0.001) and SBP percentile (β=-0.21, P=0.045).

Strategies for preserving residual renal function in peritoneal dialysis patients

Although there have been many advancements in the treatment of patients with chronic kidney disease (CKD) over the last 50 years, in terms of reducing cardiovascular risk, mortality remains unacceptably high, particularly for those patients who progress to stage 5 CKD and initiate dialysis (CKD5d). As mortality risk increases exponentially with progressive CKD stage, the question arises as to whether preservation of residual renal function once dialysis has been initiated can reduce mortality risk. Observational studies to date have reported an association between even small amounts of residual renal function and improved patient survival and quality of life. Dialysis therapies predominantly provide clearance for small water-soluble solutes, volume and acid-base control, but cannot reproduce the metabolic functions of the kidney. As such, protein-bound solutes, advanced glycosylation end-products, middle molecules and other azotaemic toxins accumulate over time in the anuric CKD5d patient. Apart from avoiding potential nephrotoxic insults, observational and interventional trials have suggested that a number of interventions and treatments may potentially reduce the progression of earlier stages of CKD, including targeted blood pressure control, reducing proteinuria and dietary intervention using combinations of protein restriction with keto acid supplementation. However, many interventions which have been proven to be effective in the general population have not been equally effective in the CKD5d patient, and so the question arises as to whether these treatment options are equally applicable to CKD5d patients. As strategies to help preserve residual renal function in CKD5d patients are not well established, we have reviewed the evidence for preserving or losing residual renal function in peritoneal dialysis patients, as urine collections are routinely collected, whereas few centres regularly collect urine from haemodialysis patients, and haemodialysis dialysis patients are at risk of sudden intravascular volume shifts associated with dialysis treatments. On the other hand, peritoneal dialysis patients are exposed to a variety of hypertonic dialysates and episodes of peritonitis. Whereas blood pressure control, using an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB), and low-protein diets along with keto acid supplementation have been shown to reduce the rate of progression in patients with earlier stages of CKD, the strategies to preserve residual renal function (RRF) in dialysis patients are not well established. For peritoneal dialysis patients, there are additional technical factors that might aggravate the rate of loss of residual renal function including peritoneal dialysis prescriptions and modality, bio-incompatible dialysis fluid and over ultrafiltration of fluid causing dehydration. In this review, we aim to evaluate the evidence of interventions and treatments, which may sustain residual renal function in peritoneal dialysis patients.

Preserving residual renal function in dialysis: what we know

Residual renal function confers a survival benefit among dialysis patients thought to be related to greater volume removal and solute clearance. Whether the presence of residual renal function is protective or merely a marker for better health is not clear. The basic mechanisms governing the decline or persistence of residual renal function are poorly understood and few studies have examined the role of medical therapy in its preservation. Dialysis modality, inflammatory processes often associated with comorbid diseases (including diabetes mellitus and obesity), volume dysregulation, and vitamin D deficiency are predictive of residual renal function decline. We review potential mechanisms for preservation of remaining glomerular filtration rate among chronic dialysis patients.

Inflammation and myocardial damage markers influence loss of residual renal function in peritoneal dialysis patients

BACKGROUND

Residual renal function (RRF) has been identified as the most important component in dialysis adequacy and has a strong effect on clinical outcomes. This justifies any effort in understanding the mechanism behind the preservation or decline in RRF. The aim of this study was to analyze the possible association of components of cardio-renal syndrome with the rate of decline in RRF.

METHODS

A retrospective cohort study was performed in a group of prevalent adult patients on continuous ambulatory peritoneal dialysis (CAPD). Patients were analyzed at baseline and after a 30-month follow-up. Evaluations included measurements of residual renal function, dialysis adequacy parameters, cardiovascular comorbidity, and measurements of biochemical markers of cardiovascular disease (CVD) and inflammation, as well as resting electrocardiography.

RESULTS

We included 129 patients in the study who were divided into groups according to loss of RRF, considering the cut-off point as 100 mL/day of 24 h urine volume. At baseline, there were no differences between groups: patients who lost RRF showed low values of 24 h urine volume, higher levels of systolic blood pressure, N-terminal pro-brain natriuretic peptide (NT-proBNP), C-reactive protein (CRP), IL-6, and low values of serum albumin. In the multivariate analysis, age, albumin, CRP, and NT-proBNP were significant risk factors for the loss of RRF.

CONCLUSIONS

Data indicate a close relationship between heart and kidney function where chronic kidney disease (CKD) affects and is an effect of, heart function, indicative of a bi-directional influence that leads to a vicious cycle, promoting deleterious effects on both systems.

Comparative outcomes between continuous ambulatory and automated peritoneal dialysis: a narrative review

Automated methods for delivering peritoneal dialysis (PD) to persons with end-stage renal disease continue to gain popularity worldwide, particularly in developed countries. However, the endeavor to automate the PD process has not been advanced on the strength of high-level evidence for superiority of automated over manual methods. This article summarizes available studies that have shed light on the evidence that compares the association of treatment with continuous ambulatory PD or automated PD (APD) with clinically meaningful outcomes. Published evidence, primarily from observational studies, has been unable to demonstrate a consistent difference in residual kidney function loss rate, peritonitis rate, maintenance of euvolemia, technique survival, mortality, or health-related quality of life in individuals undergoing continuous ambulatory PD versus APD. At the same time, the future of APD technology appears ripe for further improvement, such as the incorporation of voice commands and expanded use of telemedicine. Given these considerations, it appears that patient choice should drive the decision about PD modality.

Residual renal function in children treated with chronic peritoneal dialysis

Residual renal function (RRF) in patients with end-stage renal disease (ESRD) receiving renal replacement therapy is defined as the ability of native kidneys to eliminate water and uremic toxins. Preserved RRF improves survival and quality of life in adult ESRD patients treated with peritoneal dialysis. In children, RRF was shown not only to help preserve adequacy of renal replacement therapy but also to accelerate growth rate, improve nutrition and blood pressure control, reduce the risk of adverse myocardial changes, facilitate treatment of anemia and calcium-phosphorus balance abnormalities, and result in reduced serum and dialysate fluid levels of advanced glycation end-products. Factors contributing to RRF loss in children treated with peritoneal dialysis include the underlying renal disease such as hemolytic-uremic syndrome and hereditary nephropathy, small urine volume, severe proteinuria at the initiation of renal replacement therapy, and hypertension. Several approaches can be suggested to decrease the rate of RRF loss in pediatric patients treated with chronic peritoneal dialysis: potentially nephrotoxic drugs (e.g., aminoglycosides), episodes of hypotension, and uncontrolled hypertension should be avoided, urinary tract infections should be treated promptly, and loop diuretics may be used to increase salt and water excretion.

Controversies in timing of dialysis initiation and the role of race and demographics

Dialysis remains the predominant form of renal replacement therapy in the United States, but the optimal timing for the initiation of dialysis remains poorly defined. Not only clinical factors such as signs/symptoms of uremia, co-existing cardiovascular disease, and presence of diabetes but also key demographic characteristics including age, gender, race/ethnicity, and socioeconomics have all been considered as potential modifying factors in the decision for the timing of dialysis initiation. The 2012 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline for the Evaluation and Management of chronic kidney disease (CKD) suggests that dialysis be initiated when signs/symptoms attributable to kidney failure such as serositis, acid-base or electrolyte abnormalities, pruritus, poorly controlled volume status or blood pressure, deteriorating nutritional status despite dietary intervention, or cognitive impairment are visible or noted. These signs/symptoms typically occur when the glomerular filtration rate (GFR) is in the range of 5-10 ml/minute/1.73 m(2) , although they may occur at higher levels of GFR. We review recent data on the timing of dialysis initiation, their implications for managing patients with late-stage CKD, and the important role of considering key demographics in making patient-centered decisions for the timing of dialysis initiation.

Peritoneal dialysis as compared with hemodialysis is associated with higher overhydration but non-inferior blood pressure control and heart function

BACKGROUND/AIMS

Fluid overload is an important factor causing cardiovascular complications in dialysis patients. We compared fluid status, blood pressure (BP) and heart function between peritoneal dialysis (PD) patients and hemodialysis (HD) patients.

METHODS

We recruited 94 PD and 75 HD patients in our hospital. Fluid status was assessed by bioimpedance spectroscopy. Home BP was recorded. Use of antihypertensives was retrieved by chart review. In each group, 39 patients received echocardiographic examinations.

RESULTS

PD patients' fluid status was similar to that of predialysis HD patients. PD patients had lower systolic BP. E/E' and left ventricular mass index (LVMI) showed no significant intergroup difference. In multiple linear regression analyses, overhydration (OH)/extracellular water ratio >0.15 was associated with higher systolic BP, E/E' and LVMI.

CONCLUSIONS

While PD was associated with higher OH but non-inferior BP control and heart function, OH was indeed related to poor BP control, diastolic dysfunction and left ventricular hypertrophy.

Time course of peritoneal function in automated and continuous peritoneal dialysis

BACKGROUND AND OBJECTIVES

In automated peritoneal dialysis (APD), a patient's peritoneal membrane is more intensively exposed to fresh dialysate than it is in continuous ambulatory peritoneal dialysis (CAPD). Our aim was to study, in incident peritoneal dialysis (PD) patients, the influence of APD-compared with that of CAPD-on peritoneal transport over 4 years.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

Patients were included if at least 2 annual standard permeability analyses (SPAs) performed with 3.86% glucose were available while the patient was using the same modality with which they had started PD (APD or CAPD). Patients were followed until their first modality switch. Differences in the pattern of SPA outcomes over time were tested using repeated-measures models adjusted for age, sex, comorbidity, primary kidney disease, and year of PD start.

RESULTS

The 59 CAPD patients enrolled were older than the 47 APD patients enrolled (mean age: 58 ± 14 years vs 49 ± 14 years; p < 0.01), and they had started PD earlier (mean start year: 2000 vs 2002). Over time, no differences in solute (p > 0.19) or fluid transport (p > 0.13) were observed. Similarly, free water transport (p = 0.43) and small-pore transport (p = 0.31) were not different between the modalities. Over time, patients on APD showed a faster decline in effective lymphatic absorption rate (ELAR: p = 0.02) and in transcapillary ultrafiltration (TCUF: p = 0.07, adjusted p = 0.05). Further adjustment did not change the results.

CONCLUSIONS

Compared with patients starting on CAPD, those starting on APD experienced a faster decline in ELAR and TCUF. Other transport parameters were not different over time between the groups.

Emerging importance of residual renal function in end-stage renal failure

Residual renal function (RRF) is well recognized as an important marker of outcomes in peritoneal dialysis (PD), and contributes vitally to solute clearance. Recently, its importance in hemodialysis (HD) has emerged with evidence that it is strongly associated with improved outcomes. The presence of RRF is associated with improved nutrition, reduced erythropoetin requirements, better potassium clearance, and improved quality of life. Retrospective and observational evidence is now available, which suggests that the presence of RRF is independently associated with survival and that this benefit goes beyond what is expected simply from augmentation of small solute clearance. Preservation of RRF is now considered by many to be an important aspect of dialysis strategy. Evidence in favor of one modality over another for preservation of RRF is conflicting, as are the potential benefits of biocompatible fluids in PD. In HD, the evidence in favor of biocompatible membranes is stronger. Emerging evidence is broadly in favor of angiotensin converting enzyme inhibitors for preservation of RRF. Diuretics appear to have a neutral effect. The complexities and practical difficulties in measurement of RRF have resulted in this important parameter being largely ignored in HD. Novel markers of renal function may provide alternative, simple methods of estimating RRF, which may remove the need for urine collections and simplify its measurement.

Decline in residual renal function in automated compared with continuous ambulatory peritoneal dialysis

BACKGROUND AND OBJECTIVES

We compared the decline of RRF in patients starting dialysis on APD with those starting on CAPD, because a faster decline on APD has been suggested.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

NECOSAD patients starting dialysis on APD or CAPD with RRF at baseline were included and followed for 3 years. Residual GFR (rGFR) was the mean of urea and creatinine clearances. Differences in yearly decline of rGFR were estimated in analyses with linear repeated measures models, whereas the risk of complete loss of RRF was estimated by calculating hazard ratios (HRs) for APD compared with CAPD. As-treated (AT) and intention-to-treat (ITT) designs were used. All of the analyses were adjusted for age, gender, comorbidity, and primary kidney disease and stratified according to follow-up and mean baseline GFR.

RESULTS

The 505 CAPD and 78 APD patients had no major baseline differences. No differences were found in the analyses on yearly decline of rGFR. APD patients did have a higher risk of losing RRF in the first year (ITT crude HR 2.43 [confidence interval 95%, 1.48 to 4.00], adjusted 2.66 [1.60 to 4.44]; AT crude 1.89 [1.04 to 3.45], adjusted 2.15 [1.16 to 3.98]). The higher risk of losing all RRF was most pronounced in patients with the highest rGFR at baseline (ITT; crude 3.91 [1.54 to 9.94], adjusted 1.85 to 14.17).

CONCLUSIONS

The risk of losing RRF is higher for patients starting dialysis on APD compared with those starting on CAPD, especially in the first year.

Long-Term Outcomes in Automated Peritoneal Dialysis: Similar or Better than in Continuous Ambulatory Peritoneal Dialysis?

In many parts of the world, a progressively larger proportion of chronic peritoneal dialysis (PD) patients are being treated with automated PD (APD). Increasingly, the decision to use APD is being dictated by patient and physician preference rather than being based on medical considerations. It is important to determine if the PD modality has any effect on long-term patient outcomes. Studies examining the effects of APD on residual renal function have been inconsistent, and the effect of cycler use on native renal clearances, if any, is small and probably not clinically significant. The preponderance of the evidence suggests that peritonitis rates are somewhat lower in APD patients than in patients treated with continuous ambulatory PD (CAPD). Two of three recent studies indicated that the risk for transfer to maintenance hemodialysis may be lower in APD patients, particularly in the early period after starting chronic PD. However, the risk for death in patients treated with CAPD and APD appears to be similar in most of the studies that have looked at that question. In summary, the long-term outcomes of CAPD and APD appear to be similar, and patient and physician preference are likely to increase the utilization of APD in many parts of the world.

Is it time to revisit residual renal function in haemodialysis? (Review Article)

Residual renal function (RRF) is not currently emphasized for patients undergoing haemodialysis (HD). The role of RRF is well recognized in the peritoneal dialysis population as studies have clearly demonstrated a survival benefit with preservation of RRF. There is however, data to suggest that RRF is important in HD patients as well. Contemporary HD therapies using high flux biocompatible synthetic dialysers, bicarbonate buffered ultrapure dialysis fluids with ultrafiltration control appear to allow better preservation of RRF. The long held belief that peritoneal dialysis is better at preserving RRF than HD may no longer be true. More robust studies are required to determine the relative importance of RRF in HD and strategies to best preserve this vital asset.

Residual renal function and dialysis modality: Is it really beneficial to preserve residual renal function in dialysis patients? (Review Article)

Residual renal function (RRF) contributes to the achievement of treatment adequacy in stage 5 chronic kidney disease (CKD-5) patients. It may facilitate patients' acceptance of renal replacement therapy (RRT) in allowing reduction of treatment time duration and minimising dietary and fluid restriction. It has been confirmed to improve dialysis patient outcomes. Attempts to preserve RRF in incident Stage 5 chronic kidney disease patients are still subject to intense controversies in the nephrology community. The aim of this review is to analyse the role of renal replacement modalities in the maintenance of RRF in dialysis patients. Under the scope of this manuscript, four questions are explored: Is the preservation of residual renal function an objective for dialysis adequacy? Does dialysis modality affect the decline of RRF? What are the factors implicated by this loss of RRF? At what expense can the maintenance of RRF be achieved in dialysis patients? Preservation of RRF is undoubtedly an interesting means to enhance the efficacy of renal replacement therapy and reduce dietary fluid restriction but it should not be considered as a goal of dialysis adequacy in dialysis patients. Further, preservation of RRF must be considered as a permanent trade-off between patient comfort and chronic fluid volume overload.