The contribution of residual renal function to overall nutritional status in chronic haemodialysis patients

Residual Kidney Function in Hemodialysis: Its Importance and Contribution to Improved Patient Outcomes

Individuals afflicted with advanced kidney dysfunction who require dialysis for medical management exhibit different degrees of native kidney function, called residual kidney function (RKF), ranging from nil to appreciable levels. The primary focus of this manuscript is to delve into the concept of RKF, a pivotal yet under-represented topic in nephrology. To begin, we unpack the definition and intrinsic nature of RKF. We then juxtapose the efficiency of RKF against that of hemodialysis in preserving homeostatic equilibrium and facilitating physiological functions. Given the complex interplay of RKF and overall patient health, we shed light on the extent of its influence on patient outcomes, particularly in those living with advanced kidney dysfunction and on dialysis. This manuscript subsequently presents methodologies and measures to assess RKF, concluding with the potential benefits of targeted interventions aimed at preserving RKF.

Longitudinal Changes in Kidney Solute Clearance in a Prospective Cohort of Patients Initiating Chronic Hemodialysis

Introduction

Longitudinal changes in residual kidney function have not been well-examined in patients starting chronic hemodialysis (HD).

Methods

We analyzed urine volume and kidney solute clearances from timed urine collections and corresponding plasma samples from 42 patients randomized to incremental HD (n = 21) and conventional HD (n = 21) in the TwoPlus pilot study. Samples were collected before HD initiation (baseline); and at 6, 12, 24, and 48 weeks. We assessed temporal trends in urine volume, kidney urea and creatinine clearance, and correlations between urine volume and kidney solute clearance.

Results

Residual kidney function parameters in all patients declined over time; the pattern of decline differed between urine volume and kidney solute clearances. Urine volume declined at a steady rate with median (quartile 1, quartile 3) percentage change relative to baseline of -10% (-36 to 29) at week 6 and -47% (-76 to 5) by week 48. Kidney urea and creatinine clearances exhibited a larger decline than urine volume at week 6, -32% (-61 to 8) and -47% (-57 to -20), respectively. The rate of decline subsequently slowed, reaching about 61% decline for both solutes by week 48. Conventional HD demonstrated larger declines in urine volume and kidney urea clearance than incremental HD at week 6. Urine volume showed moderate correlation with urea (R = 0.47) and weaker correlation with creatinine (R = 0.34).

Conclusion

Despite gradual decrement in urine volume and kidney solute clearances, residual kidney function persists nearly 1 year after HD initiation. This knowledge could motivate increased practice of individualizing HD prescriptions by incorporating residual kidney function.

Benefits of Preserving Residual Urine Output in Patients Undergoing Maintenance Haemodialysis

Introduction

Chronic kidney disease is a widespread medical problem that leads to higher morbidity, mortality, and a decrease in the overall well-being of the general population. This is especially expressed in patients with end-stage renal disease (ESRD) undergoing maintenance haemodialysis. Several variables could be used to evaluate those patients' well-being and mortality risk. One of them is the presence of residual urine output.

Materials and Methods

The study was conducted on 485 patients treated with maintenance haemodialysis. After enrollment in the study, which consisted of medical history, physical examination, hydration assessment, and blood sampling, each patient was followed up for 24 months. We used residual urine output (RUO) as a measure of residual renal function (RRF). The entire cohort was divided into 4 subgroups based on the daily urinary output (<=100mL per day, >100mL to <=500mL, >500mL to <=1000mL and >1000mL).

Results

The data show that the mortality rate was significantly higher in groups with lower RUO, which was caused mainly by cardiovascular events. Also, patients with higher RUO achieved better sodium, potassium, calcium, and phosphate balance. They were also less prone to overhydration and had a better nutritional status. Preserved RRF also had a positive impact on markers of cardiovascular damage, such as NT-proBNP as well as TnT.

Conclusion

In conclusion, preserving residual urine output in ESRD patients undergoing maintenance haemodialysis is invaluable in reducing their morbidity and mortality rates and enhancing other favourable parameters of those patients.

Early as compared to late initiation of twice-weekly hemodialysis and short-term survival among end-stage renal disease patients

INTRODUCTION

The impact of timing of hemodialysis (HD) for end-stage renal disease (ESRD) patients treated with twice-weekly HD remains unclear. We aimed to determine the effects of late initiation of HD on short-term mortality and hospitalization.

METHODS

A multicenter cohort study was conducted in 11 HD centers in Northeastern Thailand (HEmodialysis Network of the NorthEastern Thailand study group). We recruited adult ESRD patients who were treated with twice-weekly HD for more than 3 months and had data on eGFR at HD initiation. Clinical and laboratory values at the time of recruitment were recorded. Late and early (eGFR at start <5 and >5 ml/min/1.73 m² ) initiations were defined. Outcomes were disease-related death (excluding any accidental deaths) and first hospitalization. Data analysis was performed by multivariable cox-regression analysis.

FINDINGS

A total of 407 patients who had data on eGFR at HD initiation (303 in late group and 104 in early group) were included for analysis. There were 56.8% male with a mean age of 55 years. During the 15.1 months of follow-up, there were 27 (6.6%) disease-related deaths. The 1-year survival rate was similar among late and early initiation groups. The incidence density of first hospitalization in the late group was significantly lower than those in the early group (HR adjusted, 0.63; 95% CI, 0.40-0.99, p = 0.047). Among 303 patients who were in the late start group, patients with diabetes had a higher mortality rate (HR, 3.49; 95% CI, 1.40-8.70, p = 0.007) when compared to non-diabetic patients.

DISCUSSION

Early initiation of HD at eGFR >5 ml/min/1.73 m² had no short-term survival benefit compared to the late group in ESRD patients treated with twice-weekly HD for at least 3 months in a resource-limited setting. A survival benefit from an early start of HD was found among diabetic patients.

Estimated Glomerular Filtration Rate in Chronic Kidney Disease: A Critical Review of Estimate-Based Predictions of Individual Outcomes in Kidney Disease

Chronic kidney disease (CKD) is generally regarded as a final common pathway of several renal diseases, often leading to end-stage kidney disease (ESKD) and a need for renal replacement therapy. Estimated GFR (eGFR) has been used to predict this outcome recognizing its robust association with renal disease progression and the eventual need for dialysis in large, mainly cross-sectional epidemiological studies. However, GFR is implicitly limited as follows: (1) GFR reflects only one of the many physiological functions of the kidney; (2) it is dependent on several non-renal factors; (3) it has intrinsic variability that is a function of dietary intake, fluid and cardiovascular status, and blood pressure especially with impaired autoregulation or medication use; (4) it has been shown to change with age with a unique non-linear pattern; and (5) eGFR may not correlate with GFR in certain conditions and disease states. Yet, many clinicians, especially our non-nephrologist colleagues, tend to regard eGFR obtained from a simple laboratory test as both a valid reflection of renal function and a reliable diagnostic tool in establishing the diagnosis of CKD. What is the validity of these beliefs? This review will critically reassess the limitations of such single-focused attention, with a particular focus on inter-individual variability. What does science actually tell us about the usefulness of eGFR in diagnosing CKD?

Incremental Versus Standard (Full-Dose) Peritoneal Dialysis

Incremental peritoneal dialysis (PD), defined as less than “standard dose” PD prescription, has a number of possible benefits, including better preservation of residual kidney function (RKF), reduced risk of peritonitis, lower peritoneal glucose exposure, lesser environmental impact, and reduced costs. Patients commencing PD are often new to kidney replacement therapy and possess substantial RKF, which may allow safe delivery of an incremental prescription, often in the form of lower frequency or duration of PD. This has the potential to help improve quality of life (QOL) and life participation through reducing time requirements and burden of treatment. Alternatively, incremental PD could potentially contribute to reduced small solute clearance, fluid overload, or patient reluctance to increase dialysis prescription when later needed. This review discusses the definition, rationale, uptake, potential advantages and disadvantages, and clinical trial evidence pertaining to the use of incremental PD.

An effective model for predicting serum albumin level in hemodialysis patients

Patients on hemodialysis (HD) are known to be at an increased risk of mortality. Hypoalbuminemia is one of the most important risk factors of death in HD patients, and is an independent risk factor for all-cause mortality that is associated with cardiac death, infection, and Protein-Energy Wasting (PEW). It is a clinical challenge to elevate serum albumin level. In addition, predicting trends in serum albumin level is effective for personalized treatment of hypoalbuminemia. In this study, we analyzed a total of 3069 records collected from 314 HD patients using a machine learning method that is based on an improved binary mutant quantum grey wolf optimizer (MQGWO) combined with Fuzzy K-Nearest Neighbor (FKNN). The performance of the proposed MQGWO method was evaluated using a series of experiments including global optimization experiments, feature selection experiments on open data sets, and prediction experiments on an HD dataset. The experimental results showed that the most critical relevant indicators such as age, presence or absence of diabetes, dialysis vintage, and baseline albumin can be identified by feature selection. Remarkably, the accuracy and the specificity of the method were 98.39% and 96.77%, respectively, demonstrating that this model has great potential to be used for detecting serum albumin level trends in HD patients.

Novel options for failing allograft in kidney transplanted patients to avoid or defer dialysis therapy

PURPOSE OF REVIEW

Despite improvement in short-term renal allograft survival in recent years, renal transplant recipients (RTR) have poorer long-term allograft outcomes. Allograft function slowly declines with periods of stable function similar to natural progression of chronic kidney disease in nontransplant population. Nearly all RTR transitions to failing renal allograft (FRG) period and require transition to dialysis. Conservative chronic kidney disease management before transition to end-stage renal disease is an increasingly important topic; however, there is limited data in RTR regarding how to delay dialysis initiation with conservative management.

RECENT FINDINGS

Since immunological and nonimmunological factors unique to RTR contribute to decline in allograft function, therapies to slow progression of FRG should take both sets of factors into account. Renal replacement therapy either incremental dialysis or rekidney transplantation should be explored. This required taking benefits and risks of continuing immunosuppressive medications into account when allograft nephrectomy may be necessary.

SUMMARY

FRG may benefit from various interventions to slow progression of worsening allograft function. Until there are stronger evidence to guide interventions to preserve renal function, extrapolating evidence from nontransplant patients and clinical judgment are necessary. The goal is to provide individualized care for conservative management of RTR with FRG.

Factors affecting the relationship between ionized and corrected calcium levels in peritoneal dialysis patients: a retrospective cross-sectional study

BACKGROUND

Chronic kidney disease-mineral and bone disorder (CKD-MBD) management in patients with end-stage renal disease is important owing to the risk of cardiovascular diseases. In clinical practice, we manage patients not by monitoring the levels of biologically active ionized calcium (iCa) but by monitoring total serum calcium or corrected calcium (cCa). We previously reported that iCa/cCa ratio was different between patients with hemodialysis and those with peritoneal dialysis (PD). In PD patients, several factors are expected to affect iCa/cCa ratio. Therefore, modifying the strategy to achieve better CKD-MBD management might be necessary; however, no reports have studied this to date. Therefore, we investigated the factors influencing iCa/cCa ratio in PD patients.

METHODS

This retrospective cross-sectional study examined background and laboratory data, including iCa, collected at routine outpatient visits. The patients were divided into the first, second, and third tertile of iCa/cCa ratio groups to compare patient background and laboratory data. Multiple regression analysis was used to investigate the factors influencing iCa/cCa ratio. We used multiple imputation to deal with missing covariate data.

RESULTS

In total, 169 PD patients were enrolled. In PD patients with lower iCa/cCa ratio, PD duration was longer and pH was higher. Urine volume and weekly renal Kt/V were lower in the patients with lower iCa/cCa ratio than in those with higher iCa/cCa ratio. iCa/cCa ratio and weekly renal Kt/V were directly correlated (r = 0.41, p < 0.01), and weekly renal Kt/V and pH were independent factors affecting iCa/cCa ratio (t = 2.86, p < 0.01 and t = - 5.42, p < 0.01, respectively).

CONCLUSIONS

iCa levels were lower in PD patients with lower residual renal function (RRF) even though their cCa levels were equal to those with maintained RRF, warranting caution in the assessment and management of CKD-MBD in PD patients.

Metabolic and volume status evaluation of hemodialysis patients with and without residual renal function in the long interdialytic interval

Introduction:

It is unclear whether residual renal function (RRF) in dialysis patients can attenuate the metabolic impact of the long 68-hour interdialytic interval, in which water, acid, and electrolyte accumulation occurs.

Objective:

to evaluate serum electrolyte levels, water balance, and acid-base status in dialytic patients with and without RRF over the long interdialytic interval (LII).

Methodology:

this was a single-center, cross-sectional, and analytical study that compared patients with and without RRF, defined by diuresis above 200 mL in 24 hours. Patients were weighed and serum samples were collected for biochemical and gasometric analysis at the beginning and at the end of the LII.

Results:

27 and 24 patients with and without RRF were evaluated, respectively. Patients without RRF had a higher increase in serum potassium during the LII (2.67 x 1.14 mEq/L, p < 0.001), reaching higher values at the end of the study (6.8 x 5.72 mEq/L, p < 0.001) and lower pH value at the beginning of the interval (7.40 x 7.43, p = 0.018). More patients with serum bicarbonate < 18 mEq/L (50 x 14.8%, p = 0.007) and mixed acid-base disorder (57.7 x 29.2%, p = 0.042), as well as greater interdialytic weight gain (14.67 x 8.87 mL/kg/h, p < 0.001) and lower natremia (137 x 139 mEq/L, p = 0.02) at the end of the interval. Calcemia and phosphatemia were not different between the groups.

Conclusion:

Patients with RRF had better control of serum potassium, sodium, acid-base status, and volemia throughout the LII.

Initiating haemodialysis twice-weekly as part of an incremental programme may protect residual kidney function

BACKGROUND

Initiating twice-weekly haemodialysis (2×HD) in patients who retain significant residual kidney function (RKF) may have benefits. We aimed to determine differences between patients initiated on twice- and thrice-weekly regimes, with respect to loss of kidney function, survival and other safety parameters.

METHODS

We conducted a single-centre retrospective study of patients initiating dialysis with a residual urea clearance (KRU) of ≥3 mL/min, over a 20-year period. Patients who had 2×HD for ≥3 months during the 12 months following initiation of 2×HD were identified for comparison with those dialysed thrice-weekly (3×HD).

RESULTS

The 2×HD group consisted of 154 patients, and the 3×HD group 411 patients. The 2×HD patients were younger (59 ± 15 versus 62 ± 15 years: P = 0.014) and weighed less (70 ± 16 versus 80 ± 18 kg: P < 0.001). More were females (34% versus 27%: P = 0.004). Fewer had diabetes (25% versus 34%: P = 0.04) and peripheral vascular disease (PVD) (13% versus 23%: P = 0.008). Baseline KRU was similar in both groups (5.3 ± 2.4 for 2 × HD versus 5.1 ± 2.8 mL/min for 3 × HD: P = 0.507). In a mixed effects model correcting for between-group differences in comorbidities and demographics, 3×HD was associated with increased rate of loss of KRU and separation of KRU. In separate mixed effects models, group (2×HD versus 3×HD) was not associated with differences in serum potassium or phosphate, and the groups did not differ with respect to total standard Kt/V. Survival, adjusted for age, gender, weight, baseline KRU and comorbidity (prevalence of diabetes, cardiac disease, PVD and malignancy) was greater in the 2×HD group (hazard ratio 0.755: P = 0.044). In sub-analyses, the survival benefit was confined to women, and those of less than median bodyweight.

CONCLUSION

2×HD initiation as part of an incremental programme with regular monthly monitoring of KRU was safe and associated with a reduced rate of loss of RKF early after dialysis initiation and improved survival. Randomized controlled trials of this approach are indicated.

The “Heart” of Peritoneal Dialysis: Residual Renal Function

The CANUSA study originally reported the importance of total small-solute clearance in predicting survival of peritoneal dialysis (PD) patients. However, subsequent reanalysis of data from the CANUSA study clearly demonstrated that the predictive power for mortality in PD patients was largely attributable to residual renal function (RRF) and not to the dose of PD. While this should not lead to the assumption that the dose of PD is unimportant, it does clearly indicate that the contribution of residual renal clearance and PD clearance to the overall survival of PD cannot be considered equivalent. In a previous study, we also demonstrated the importance of loss of RRF in predicting a heightened risk of mortality and cardiovascular death in PD patients. In this review, we focus our discussion on the different potential mechanisms that explain the important link between RRF and cardiovascular disease and survival of PD patients. We provide evidence to explain why RRF is so important to patients receiving long-term PD treatment and why it should be regarded as the “heart” of PD.

Relationship between residual kidney function and symptom burden in haemodialysis patients

BACKGROUND

Residual kidney function (RKF) has been associated with improved solute clearance and survival in haemodialysis (HD) patients. However, whether RKF impacts symptom burden in HD patients is unknown.

AIMS

To determine the prevalence of RKF in HD patients and to explore associations between higher levels of RKF with symptom burden, as well as clinical and biochemical parameters.

METHODS

This is a single-centre, retrospective, observational study. RKF was assessed as urea clearance (KRU) by interdialytic urine collection. Symptom burden was measured using the palliative care outcome scale renal questionnaire.

RESULTS

A total of 90 maintenance HD patients was recruited; 31.9% had KRU ≥1 mL/min/1.73 m² . Patients with KRU ≥1 mL/min/1.73 m² reported fewer symptoms (5.3 ± 3.5 vs 7.7 ± 3.8) (P = 0.011), including less shortness of breath (15% vs 55%) (P = 0.0013) and vomiting (0% vs 30%) (P = 0.0016). Higher RKF was associated with lower β₂ -microglobilin (P < 0.0001), and lower serum potassium (P = 0.02), but no difference in phosphate, haemoglobin, C-reactive protein or serum albumin.

CONCLUSION

Higher RKF was significantly associated with fewer symptoms, and lower serum β₂ -microglobulin and potassium, suggesting that strategies to preserve RKF may be beneficial.

Association of Mineral Bone Disorder With Decline in Residual Kidney Function in Incident Hemodialysis Patients

Abnormalities of mineral bone disorder (MBD) parameters have been suggested to be associated with poor renal outcome in predialysis patients. However, the impact of those parameters on decline in residual kidney function (RKF) is uncertain among incident hemodialysis (HD) patients. We performed a retrospective cohort study in 13,772 patients who initiated conventional HD during 2007 to 2011 and survived 6 months of dialysis. We examined the association of baseline serum phosphorus, calcium, intact parathyroid hormone (PTH), and alkaline phosphatase (ALP) with a decline in RKF. Decline in RKF was assessed by estimated slope of renal urea clearance (KRU) over 6 months from HD initiation. Our cohort had a mean ± SD age of 62 ± 15 years; 64% were men, 57% were white, 65% had diabetes, and 51% had hypertension. The median (interquartile range [IQR]) baseline KRU level was 3.4 (2.0, 5.2) mL/min/1.73 m² . The median (IQR) estimated 6-month KRU slope was -1.47 (-2.24, -0.63) mL/min/1.73 m² per 6 months. In linear regression models, higher phosphorus categories were associated with a steeper 6-month KRU slope compared with the reference category (phosphorus 4.0 to <4.5 mg/dL). Lower calcium and higher intact PTH and ALP categories were also associated with a steeper 6-month KRU slope compared with their respective reference groups (calcium 9.2 to <9.5 mg/dL; intact PTH 150 to <250 pg/mL; ALP <60 U/L). The increased number of parameter abnormalities had an additive effect on decline in RKF. Abnormalities of MBD parameters including higher phosphorus, intact PTH, ALP and lower calcium levels were independently associated with decline in RKF in incident HD patients. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

Individualized Hemodialysis Treatment: A Perspective on Residual Kidney Function and Precision Medicine in Nephrology

Background: Residual kidney function (RKF) is often expected to inevitably and rapidly decline among hemodialysis patients and, hence, has been inadvertently ignored in clinical practice. The importance of RKF has been revisited in some recent studies. Given that patients with end-stage renal disease now tend to initiate maintenance hemodialysis therapy with higher RKF levels, there seem to be important opportunities for incremental hemo­dialysis by individualizing the dose and frequency according to their RKF levels. This approach is realigned with precision medicine and patient-centeredness. Summary: In this article, we first review the available methods to estimate RKF among hemodialysis patients. We then discuss the importance of maintaining and monitoring RKF levels based on a variety of clinical aspects, including volume overload, blood pressure control, mineral and bone metabolism, nutrition, and patient survival. We also review several potential measures to protect RKF: the use of high-flux and biocompatible membranes, the use of ultrapure dialysate, the incorporation of hemodiafiltration, incremental hemodialysis, and a low-protein diet, as well as general care such as avoiding nephrotoxic events, maintaining appropriate blood pressure, and better control of mineral and bone disorder parameters. Key Message: Individualized hemodialysis regimens may maintain RKF, lead to a better quality of life without compromising long-term survival, and ensure precision medicine and patient-centeredness in nephrology practice.

The protective effect of different dialysis types on residual renal function in patients with maintenance hemodialysis: A systematic review and meta-analysis

BACKGROUND

Residual renal function (RRF) is an important determinant of mortality and morbidity in patients undergoing hemodialysis. Different dialysis types may have different effects on RRF. We therefore conducted this meta-analysis to examine the RRF protective effect of different dialysis types for hemodialysis patients.

METHODS

A systematic search was performed on PubMed, EMbase, Web of Science, Chinese Biomedical Literature Database, Wanfang database, and China National Knowledge Infrastructure for randomized controlled trials and cohort studies. Dialysis types included low-flux hemodialysis (LFHD), high-flux hemodialysis (HFHD), hemodiafiltration (HDF), and hemodialysis and hemoperfusion (HD+HP). The mean of endogenous creatinine clearance rate (CCR) and urea clearance rate (Curea), or urine volume was used to estimate RRF [95% confidence interval (95% CI), 6.05-16.80].

RESULTS

There were 12 articles involving 1224 patients, including 11 random controlled trials and 1 cohort study. Meta-analysis showed that the RRF protective effect of HFHD [mean difference (MD) = 1.48, 95% CI (2.11 to 0.86), P < .01] and HD+HP [MD = 0.41, 95% CI (0.69 to 0.12), P = .005] was better than that of LFHD, and the RRF decline rate was the lowest in HFHD group [MD = 0.13, 95% CI (0.17 to 0.09), P < .01]. Descriptive analysis showed that HDF could better protect RRF when compared with LFHD. However, there was no consistency among other interventions when removing LFHD due to limited data.

CONCLUSION

For patients undergoing maintenance hemodialysis, the HFHD, HD+HP and HDF may better protect RRF, compared with LFHD.

Incremental dialysis for preserving residual kidney function-Does one size fit all when initiating dialysis?

While many patients have substantial residual kidney function (RKF) when initiating hemodialysis (HD), most patients with end stage renal disease in the United States are initiated on 3-times per week conventional HD regimen, with little regard to RKF or patient preference. RKF is associated with many benefits including survival, volume control, solute clearance, and reduced inflammation. Several strategies have been recommended to preserve RKF after HD initiation, including an incremental approach to HD initiation. Incremental HD prescriptions are personalized to achieve adequate volume control and solute clearance with consideration to a patient's endogenous renal function. This allows the initial use of less frequent and/or shorter HD treatment sessions. Regular measurement of RKF is important because HD frequency needs to be increased as RKF inevitably declines. We narratively review the results of 12 observational cohort studies of twice-weekly compared to thrice-weekly HD. Incremental HD is associated with several benefits including preservation of RKF as well as extending the event-free life of arteriovenous fistulas and grafts. Patient survival and quality of life, however, has been variably associated with incremental HD. Serious risks must also be considered, including increased hospitalization and mortality perhaps related to fluid and electrolyte shifts after a long interdialytic interval. On the basis of the above literature review, and our clinical experience, we suggest patient characteristics which may predict favorable outcomes with an incremental approach to HD. These include substantial RKF, adequate volume control, lack of significant anemia/electrolyte imbalance, satisfactory health-related quality of life, low comorbid disease burden, and good nutritional status without evidence of hypercatabolism. Clinicians should engage patients in on-going conversations to prepare for incremental HD initiation and to ensure a smooth transition to thrice-weekly HD when needed.

Association Between Comprehensive Nutritional Scoring System (CNSS) and Outcomes of Continuous Ambulatory Peritoneal Dialysis Patients

BACKGROUND/AIMS

The presence of protein-energy wasting (PEW) among dialysis patients is a crucial risk factor for outcomes. The complicated pathogenesis of PEW makes it difficult to assess and treat. This single-center retrospective study focuses on the association between nutritional markers and the outcomes of continuous ambulatory peritoneal dialysis(CAPD) patients, aiming to establish a practical comprehensive nutritional scoring system for CAPD patients.

METHODS

924 patients who initiated peritoneal dialysis in our center from January 1st,2005 to December 31st,2015 were enrolled. Comprehensive nutritional scoring system(CNSS) was based on items including SGA, BMI, ALB, TC, MAC and TSF. We divide patients into 3 groups according to their CNSS score. Outcomes including mortality, hospitalization days and hospitalization frequency were compared between 3 grades.

RESULTS

The CNSS grade correlated significantly with hospitalization days (P<0.05). Both categorized CNSS grade (HR:0.56; 95% CI:0.41-0.78; P = 0.001) and continuous CNSS score (HR:0.87; 95% CI: 0.80-0.94; P = 0.001) independently protect PD patients from all-cause mortality.

CONCLUSION

CNSS provides an integrated scoring system with significant associations with hospitalization and mortality in PD patients. The CNSS grade differentiates patients with malnutritional risk and independently predicts high risk of morbidity and mortality.

Vascular calcification and cardiac function according to residual renal function in patients on hemodialysis with urination

Background

Vascular calcification is common and may affect cardiac function in patients with end-stage renal disease (ESRD). However, little is known about the effect of residual renal function on vascular calcification and cardiac function in patients on hemodialysis.

Methods

This study was conducted between January 2014 and January 2017. One hundred six patients with residual renal function on maintenance hemodialysis for 3 months were recruited. We used residual renal urea clearance (KRU) to measure residual renal function. First, abdominal aortic calcification score (AACS) and brachial-ankle pulse wave velocity (baPWV) were measured in patients on hemodialysis. Second, we performed echocardiography and investigated new cardiovascular events after study enrollment.

Results

The median KRU was 0.9 (0.3–2.5) mL/min/1.73m². AACS (4.0 [1.0–10.0] vs. 3.0 [0.0–8.0], p = 0.05) and baPWV (1836.1 ± 250.4 vs. 1676.8 ± 311.0 cm/s, p = 0.01) were significantly higher in patients with a KRU < 0.9 mL/min/1.73m² than a KRU ≥ 0.9 mL/min/1.73m². Log-KRU significantly negatively correlated with log-AACS (ß = -0.29, p = 0.002) and baPWV (ß = -0.19, P = 0.05) after factor adjustment. The proportion of left ventricular diastolic dysfunction was significantly higher in patients with a KRU < 0.9 mL/min/1.73m² than with a KRU ≥ 0.9 mL/min/1.73m² (67.9% vs. 49.1%, p = 0.05). Patients with a KRU < 0.9 mL/min/1.73m² showed a higher tendency of cumulative cardiovascular events compared to those with a KRU ≥ 0.9 ml/min/1.73m² (P = 0.08).

Conclusions

Residual renal function was significantly associated with vascular calcification and left ventricular diastolic dysfunction in patients on hemodialysis.

Renin-angiotensin system blockers and residual kidney function loss in patients initiating peritoneal dialysis: an observational cohort study

Background

Although angiotensin-converting enzyme inhibitors (ACEI) and angiotensin-II receptor blockers (ARB) have been shown to preserve residual kidney function in a select group of Asian patients undergoing continuous ambulatory peritoneal dialysis (PD) in two small randomized clinical trials, the effectiveness of these drugs has yet to be demonstrated in a more diverse population of patients with multiple comorbid conditions. We investigated the association between ACEI/ARB use and development of recorded anuria in a cohort of patients initiating PD in the U.S.

Methods

We conducted a retrospective observational cohort study using the US Renal Data System and electronic health records data from a large national dialysis provider. We identified adult patients who initiated PD from 2007 to 2011. Only patients who participated in the federal prescription drug benefit program, Medicare Part D, for the first 90 days of dialysis were included. Patients who filled a prescription for an ACEI or ARB during those 90 days were considered users. We applied Cox proportional hazards models to an inverse probability of treatment-weighted (IPTW) cohort to estimate the hazard ratio (HR) for anuria (24-h urine volume < 200 ml) in ACEI/ARB users vs. non-users.

Results

Among 886 patients, 389 (44%) used an ACEI/ARB. Almost a third of these patients were black or Hispanic, and more than a quarter had comorbidities that would have excluded them from the randomized clinical trials of ACEI/ARB. Two hundred eighty patients reached anuria over 840 person-years of follow-up, for a composite event rate of 33 events per 100 person-years. We found no clear association between ACEI/ARB use and progression to anuria [HR: 0.86, 95% CI: 0.73–1.02].

Conclusions

ACEI/ARB use is common in patients initiating PD in the U.S. but was not associated with a lower risk of anuria. Residual confounding by unmeasured variables is an important limitation of this observational study. Still, these findings suggest that pragmatic clinical trials are warranted to test the effectiveness of ACEI/ARB in slowing the decline of residual kidney function in a diverse population of peritoneal dialysis patients with multiple comorbid conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0616-4) contains supplementary material, which is available to authorized users.

Hemodialysis is associated with higher serum FGF23 level when compared with peritoneal dialysis

BACKGROUND

Considering the growing relevance of fibroblast growth factor-23 (FGF23) and increased cardiovascular mortality in dialysis population, an analysis was performed to assess the influence of dialysis modality (peritoneal dialysis and hemodialysis) on level of FGF23.

METHODS

A cross-sectional study was performed in 80 continuous ambulatory peritoneal dialysis (CAPD) and 65 hemodialysis (HD) patients without residual renal function. Levels of calcium, phosphate, parathyroid hormone and FGF23 were measured, and their correlations were analyzed. Data on demographics, dialysis modality and FGF23 level were also analyzed.

RESULTS

A significant correlation was found between FGF23 and serum calcium, serum phosphate and dialysis vintage in dialysis patients. Level of FGF23 was significantly higher in hemodialysis patients than that in peritoneal dialysis population. Multivariable regression revealed that, compared to CAPD, hemodialysis was found to be a predictor for higher FGF23 level, which was independent of serum calcium and phosphate level (P < 0.05).

CONCLUSIONS

These findings demonstrate that FGF23 levels are significantly higher in hemodialysis patients than that in peritoneal dialysis patients. We demonstrate an important association between dialysis modality (HD vs CAPD) and higher FGF23, independent of classical determinants (serum calcium and phosphate level).

Incremental Hemodialysis - A European Perspective

Most patients initiating hemodialysis have residual renal function (RRF). Whereas RRF is monitored prior to commencing hemodialysis, once dialysis is started most centres simply rely on dialyzer urea clearance to determine adequate uremic toxin clearance and disregard the effect of RRF. However sustaining RRF is important for the dialysis patient, as RRF reduces inter-dialytic weight gains, increases middle molecule and protein bound toxin clearances and is associated with better quality of life assessments. Paradoxically, more frequent dialysis and longer dialysis sessions appear to be associated with more rapid loss of RRF. As such, starting patients with less frequent or shorter dialysis sessions, depending upon individual patient comorbidity, may lead to better preservation of RRF. However to prevent inadequate uremic toxin clearance or volume overload, RRF needs to be regularly monitored. Unfortunately, the 24-hour urine collection for urea and creatinine clearance remains the mainstay for RRF assessment. This measurement chiefly represents glomerular clearance rather than tubular function, but the latter may be also important for the dialysis patients. Incremental dialysis with less initial dialysis treatment may lower costs and will allow others to dialyze more frequently. The key to start a successful incremental hemodialysis approach is the regular monitoring of the patient, so that as RRF is lost an appropriate decision can be made regarding increasing dialysis session duration and frequency on an individual patient basis or consider switching modalities to hemodiafiltration.

Correlation of Residual Diuresis with MIS Score and Nutritional Status in Peritoneal Dialysis Patients: A Croatian Nationwide Study

Introduction. Residual diuresis (RD) is an important predictor of mortality and cardiovascular (CV) deaths in peritoneal dialysis (PD) patients, and contributes more to overall survival compared to PD clearance. In this study we investigated the correlation between RD and CV outcomes in PD patients.

Methods. A total of 190 PD patients from 13 dialysis centers, a national representation, were included in this analysis. Biomarkers of anemia, nutritional status [malnutrition inflammation score (MIS), subjective global assessment (SGA), serum albumin, anthropometric measurements including body mass index (BMI)], dialysis dose (Kt/V) and laboratory measurements were determined. RD was estimated using the volume of daily urine.

Results. There were 78(41.05 %) females and 112 (58.95 %) males; aged 57.35±14.41 years, on PD for 24.96±24.43 months. Fifty-six patients had diabetes type II (44 as primary kidney disease). The mean RD was 1170±673.6 ml (range 0-3000 mL). Statistically significant correlations between RD and BMI, hip circumference, time on PD, Kt/V, MIS, SGA, erythrocytes (E), Hemoglobin (Hb), PTH, and serum albumin were observed.

Conclusions. We demonstrated a significant correlation between RD and MIS score, SGA, anthropometry and albumin. Every effort should be invested to maintain RD for as long as possible to achieve optimal treatment results and to decrease CV mortality in PD population.

Changes in urine volume and serum albumin in incident hemodialysis patients

INTRODUCTION

Hypoalbuminemia is a predictor of poor outcomes in dialysis patients. Among hemodialysis patients, there has not been prior study of whether residual kidney function or decline over time impacts serum albumin levels. We hypothesized that a decline in residual kidney function is associated with an increase in serum albumin levels among incident hemodialysis patients.

METHODS

In a large national cohort of 38,504 patients who initiated hemodialysis during 1/2007-12/2011, we examined the association of residual kidney function, ascertained by urine volume and renal urea clearance, with changes in serum albumin over five years across strata of baseline residual kidney function, race, and diabetes using case-mix adjusted linear mixed effects models.

FINDINGS

Serum albumin levels increased over time. At baseline, patients with greater urine volume had higher serum albumin levels: 3.44 ± 0.48, 3.50 ± 0.46, 3.57 ± 0.44, 3.59 ± 0.45, and 3.65 ± 0.46 g/dL for urine volume groups of <300, 300-<600, 600-<900, 900-<1,200, and ≥1,200 mL/day, respectively (P_trend  < 0.001). Over time, urine volume and renal urea clearance declined and serum albumin levels rose, while the baseline differences in serum albumin persisted across groups of urinary volume. In addition, the rate of decline in residual kidney function was not associated with the rate of change in albumin.

DISCUSSION

Hypoalbuminemia in hemodialysis patients is associated with lower residual kidney function. Among incident hemodialysis patients, there is a gradual rise in serum albumin that is independent of the rate of decline in residual kidney function, suggesting that preservation of residual kidney function does not have a deleterious impact on serum albumin levels.

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.

Protective effect of mycophenolate mofetil on residual renal function in peritoneal dialysis patients: An open label feasibility study

AIM

This study aims to evaluate the safety of mycophenolate mofetil (MMF) and its effect on residual renal function (RRF) during peritoneal dialysis (PD).

METHODS

This is a prospective, randomized study comprising 60 PD patients. The patients were assigned either to the MMF group (MMF dosage: 1.0-1.5 g/day in two divided doses for 6 months, followed by a dose of 0.5-0.75 g/day for another 6 months) or to the control group. The patients close monitoring for 1 year. Variables related to residual renal function, including urine volume, measured glomerular filtration rate (GFR), and renal Kt/V, were measured at four time points.

RESULTS

There were no significant changes in urinary protein excretion in either group (P > 0.05). The MMF group showed a significantly higher urine volume than the control group (955.38 ± 243.54 vs 786.15 ± 279.62 mL/day, P = 0.024). The renal kt/V was also significantly higher in the MMF group (0.59 ± 0.11 in MMF vs 0.50 ± 0.19 in control group, P = 0.032). There was significant difference in the renal measured GFR between the two groups at 6, 9 and 12 months (MMF vs control at 6 months, 6.14 ± 0.66 vs 5.58 ± 0.65 mL/min per 1.73m² , P = 0.003; at 9 months, 5.68 ± 0.80 vs 4.78 ± 0.75, P < 0.001; at 12 months, 5.44 ± 0.91 vs 4.43 ± 0.93, P < 0.001). MMF was well tolerated without any serious complications.

CONCLUSION

The use of MMF in PD patients tends to better preserve RRF.

Preservation of residual kidney function in hemodialysis patients: reviving an old concept

Residual kidney function (RKF) may confer a variety of benefits to patients on maintenance dialysis. RKF provides continuous clearance of middle molecules and protein-bound solutes. Whereas the definition of RKF varies across studies, interdialytic urine volume may emerge as a pragmatic alternative to more cumbersome calculations. RKF preservation is associated with better patient outcomes including survival and quality of life and is a clinical parameter and research focus in peritoneal dialysis. We propose the following practical considerations to preserve RKF, especially in newly transitioned (incident) hemodialysis patients: (1) periodic monitoring of RKF in hemodialysis patients through urine volume and including residual urea clearance with dialysis adequacy and outcome markers such as anemia, fluid gains, minerals and electrolytes, nutritional, status and quality of life; (2) avoidance of nephrotoxic agents such as radiocontrast dye, nonsteroidal anti-inflammatory drugs, and aminoglycosides; (3) more rigorous hypertension control and minimizing intradialytic hypotensive episodes; (4) individualizing the initial dialysis prescription with consideration of an incremental/infrequent approach to hemodialysis initiation (e.g., twice weekly) or peritoneal dialysis; and (5) considering a lower protein diet, especially on nondialysis days. Because RKF appears to be associated with better patient outcomes, it requires more clinical and research focus in the care of hemodialysis and peritoneal dialysis patients.

Association Between Hemodiafiltration and Hypoalbuminemia in Middle-Age Hemodialysis Patients

The advantage of hemodiafiltration (HDF) is well known. One of the disadvantages of HDF is loss of serum albumin, but this issue is still obscure. Some risk factors associated with mortality were age dependent. Studies on serum albumin/hypoalbuminemia and HDF in different age stratification were limited. The aim of this cross-sectional study was to assess the role of HDF and other clinical variables on serum albumin values in maintenance hemodialysis (MHD) patients of different age groups. We recruited a total of 1216 patients on MHD. Patients were divided into 4 groups by age stratification of youth (<30 years old), young-middle age (30-44 years old), middle age (45-64 years old), and old age (≥65  years old). Biochemical, hematological, nutritional, inflammatory parameters, and receiving HDF or not were recorded. The associations between age groups, HDF, and variables mentioned above were analyzed. Only in middle-age group, patients with HDF was significantly (P = 0.013) associated with serum albumin <4 g/dL. In middle-age group, a multivariate-forward logistic regression analysis showed that male sex (2.169 [1.029, 4.574], P = 0.042), inflammation (4.167 [2.043, 8.498], P < 0.001), cardiovascular disease (2.92 [1.019, 8.402], P = 0.046), serum creatinine level (0.639 [0.538, 0.758], P < 0.001), and cholesterol level (0.984 [0.975, 0.993], P = 0.001) were associated with serum albumin level <3.6 g/dL. Hepatitis C virus infection (1.911 [1.186, 3.077], P = 0.008), HDF (2.143 [1.298, 3.540], P = 0.003), inflammation (2.309 [1.549, 3.440], P < 0.001), use of arterio-venous fistula (0.518 [0.327, 0.820], P = 0.005), Kt/V (0.395 [0.193, 0.809], P = 0.011), nonanuria (0.542 [0.337, 0.870], P = 0.011), serum creatinine level (0.744 [0.669, 0.828], P < 0.001), and cholesterol level (0.993 [0.987, 0.998], P = 0.013) were associated with serum albumin level <4 g/dL. HDF can predict serum albumin level <4 g/dL in middle-age HD patients. The effect of age needs to be taken into consideration when interpreting the correlation between hypoalbuminemia and HDF.

Predicting residual kidney function in hemodialysis patients using serum β-trace protein and β2-microglobulin

Residual kidney function (RKF) contributes significant solute clearance in hemodialysis patients. Kidney Diseases Outcomes Quality Initiative (KDOQI) guidelines suggest that hemodialysis dose can be safely reduced in those with residual urea clearance (KRU) of 2 ml/min/1.73 m(2) or more. However, serial measurement of RKF is cumbersome and requires regular interdialytic urine collections. Simpler methods for assessing RKF are needed. β-trace protein (βTP) and β2-microglobulin (β2M) have been proposed as alternative markers of RKF. We derived predictive equations to estimate glomerular filtration rate (GFR) and KRU based on serum βTP and β2M from 191 hemodialysis patients based on standard measurements of KRU and GFR (mean of urea and creatinine clearances) using interdialytic urine collections. These modeled equations were tested in a separate validation cohort of 40 patients. A prediction equation for GFR that includes both βTP and β2M provided a better estimate than either alone and contained the terms 1/βTP, 1/β2M, 1/serum creatinine, and a factor for gender. The equation for KRU contained the terms 1/βTP, 1/β2M, and a factor for ethnicity. Mean bias between predicted and measured GFR was 0.63 ml/min and 0.50 ml/min for KRU. There was substantial agreement between predicted and measured KRU at a cut-off level of 2 ml/min/1.73 m(2). Thus, equations involving βTP and β2M provide reasonable estimates of RKF and could potentially be used to identify those with KRU of 2 ml/min/1.73 m(2) or more to follow the KDOQI incremental hemodialysis algorithm.

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.

Sonographic measurement of renal size in patients undergoing chronic hemodialysis: Correlation with residual renal function

Previous studies have reported that renal size may change when the function is compromised. However, it is not known whether sonographically measured renal size reflects the residual renal function (RRF) in patients undergoing chronic hemodialysis. A total of 140 patients undergoing chronic hemodialysis (≥3 months) were investigated in the present study. The patients were divided into two groups according to the daily urine volume: Individuals with RRF (RRF+ group; ≥200 ml; n=65) and without RRF (RRF− group; <200 ml; n=75). Renal sizes were measured using sonography and renal volumes were calculated with the ellipsoid formula. Univariable and multivariable stepwise forward logistic regression analyses were performed to examine the correlation between the presence of RRF and various variables. The results indicated that there were statistically significant differences (P<0.001) between the RRF+ and RRF− groups with regard to renal length, width, thickness and volume of the left (length, 7.9±1.2 vs. 6.8±1.2 cm; volume, 60.0±26.7 vs. 40.2±18.1 ml, respectively) and right (length, 7.6±1.2 vs. 6.7±1.2 cm; volume, 50.2±26.5 vs. 33.9±15.3 ml, respectively) sides of the kidney. Multivariable stepwise forward logistic regression analyses showed that the mean renal length or volume and hemodialysis duration were independent predictors of the presence of RRF. Therefore, renal size assessment by ultrasonography may be useful for RRF evaluation in patients undergoing chronic hemodialysis.

Strategies for the preservation of residual renal function in pediatric dialysis patients

In adults with end-stage renal disease (ESRD), the preservation of residual renal function (RRF) has been shown to be associated with decreased mortality and improved control of complications of chronic kidney disease. However, less is known on the benefits of RRF in the pediatric dialysis population. The purpose of this article is to review the clinical significance of RRF and to discuss strategies for the preservation of RRF in children with ESRD.

[Extracellular hydration status and residual urinary sodium excretion in chronic hemodialysis patients: a cross-sectional multicenter study]

BACKGROUND

In dialysis patients, a misevaluation of dry weight may lead to an increased morbidity and mortality. The aim of this cross-sectional multicenter study was to evaluate the association between residual urinary sodium excretion and extracellular volume status in chronically treated hemodialysis patients.

PATIENTS AND METHODS

Dry weight was determined clinically and by whole-body bioimpedance spectroscopy (Body Composition Monitor, Fresenius Medical Care) prior to a mid-week session in 40 chronic hemodialysis patients with significant residual diuresis (more than 250 mL per day) and receiving treatment in four dialysis centers. Regarding their hydration status assessed by the Body Composition Monitor and in comparison to a healthy reference population, patients were assigned to 1 of the 3 categories: overhydrated, normohydrated and dehydrated. Urine output, urinary sodium excretion and residual renal function were measured for all patients within 30 days before dry weight assessment.

RESULTS

The median post-HD session FO was of-0.40 L (IQR: from-1.95 to+0.90) and the median residual urinary sodium excretion was of 64 mmol/L (IQR: 46-79). Among these patients, 16 were normohydated, 16 were dehydrated and 8 were overhydrated. There was a linear relationship between the hydration status after HD session and the urinary sodium excretion (estimate: 5.6±1.5; p<0.001). Compared with normohydrated patients, overhydrated patients had a higher residual urinary sodium excretion (estimate: 26±10; p<0.01).

CONCLUSION

In this study, urinary sodium excretion is associated with the hydration status evaluated by whole-body bioimpedance spectroscopy.

Does the adequacy parameter Kt/V(urea) reflect uremic toxin concentrations in hemodialysis patients?

Hemodialysis aims at removing uremic toxins thus decreasing their concentrations. The present study investigated whether Kt/V_urea, used as marker of dialysis adequacy, is correlated with these concentrations. Predialysis blood samples were taken before a midweek session in 71 chronic HD patients. Samples were analyzed by colorimetry, HPLC, or ELISA for a broad range of uremic solutes. Solute concentrations were divided into four groups according to quartiles of Kt/V_urea, and also of different other parameters with potential impact, such as age, body weight (BW), Protein equivalent of Nitrogen Appearance (PNA), Residual Renal Function (RRF), and dialysis vintage. Dichotomic concentration comparisons were performed for gender and Diabetes Mellitus (DM). Analysis of Variance in quartiles of Kt/V_urea did not show significant differences for any of the solute concentrations. For PNA, however, concentrations showed significant differences for urea (P<0.001), uric acid (UA), p-cresylsulfate (PCS), and free PCS (all P<0.01), and for creatinine (Crea) and hippuric acid (HA) (both P<0.05). For RRF, concentrations varied for β₂-microglobulin (P<0.001), HA, free HA, free indoxyl sulfate, and free indole acetic acid (all P<0.01), and for p-cresylglucuronide (PCG), 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF), free PCS, and free PCG (all P<0.05). Gender and body weight only showed differences for Crea and UA, while age, vintage, and diabetes mellitus only showed differences for one solute concentration (UA, UA, and free PCS, respectively). Multifactor analyses indicated a predominant association of concentration with protein intake and residual renal function. In conclusion, predialysis concentrations of uremic toxins seem to be dependent on protein equivalent of nitrogen appearance and residual renal function, and not on dialysis adequacy as assessed by Kt/V_urea. Efforts to control intestinal load of uremic toxin precursors by dietary or other interventions, and preserving RRF seem important approaches to decrease uremic solute concentration and by extension their toxicity.

Infrequent dialysis: a new paradigm for hemodialysis initiation

Nearly a half-century ago, the thrice-weekly hemodialysis schedule was empirically established as a means to provide an adequate dialysis dose while also treating the greatest number of end-stage renal disease (ESRD) patients using limited resources. Landmark trials of hemodialysis adequacy have historically been anchored to thrice-weekly regimens, but a recent randomized controlled trial demonstrated that frequent hemodialysis (six times per week) confers cardiovascular and survival benefits. Based on these collective data and experience, clinical practice guidelines advise against a less than thrice-weekly treatment schedule in patients without residual renal function, yet provide limited guidance on the optimal treatment frequency when substantial native kidney function is present. Thus, during the transition from Stage 5 chronic kidney disease to ESRD, the current paradigm is to initiate hemodialysis on a "full-dose" thrice-weekly regimen even among patients with substantial residual renal function. However, emerging data suggest that frequent hemodialysis accelerates residual renal function decline, and infrequent regimens may provide better preservation of native kidney function. Given the high mortality rates during the first 6 months of hemodialysis and the survival benefits of preserved native kidney function, initiation with twice-weekly treatment schedules ("infrequent hemodialysis") with an incremental increase in frequency over time may provide an opportunity to optimize patient survival. This review outlines the clinical benefits of post-hemodialysis residual renal function, studies of twice-weekly treatment regimens, and the potential risks and benefits of infrequent hemodialysis.

Change in body composition in accordance with residual renal function in patients on peritoneal dialysis

OBJECTIVES

The aim of this study is to evaluate changes in body composition in accordance with residual renal function (RRF).

SUBJECTS AND METHODS

Two hundred forty-four patients with more than 1 year of follow-up were enrolled. The mean value of RRF at peritoneal dialysis (PD) initiation and 1 year after PD initiation was used as an indicator of the time-averaged RRF (TA-RRF). The patients were divided into 3 groups with respect to the tertile of the TA-RRF level: low tertile (n = 81), middle tertile (n = 82), and high tertile (n = 81). Body composition measurement was determined from dual-energy X-ray absorptiometry and bioimpedance analysis. This analysis was performed at PD initiation and 1 year after PD initiation.

RESULTS

Multivariate analysis showed that the high TA-RRF tertile was associated with an increase in lean mass index. Fat mass index in all tertiles and bone mineral content index in the middle and high TA-RRF tertiles were increased, but no significant difference were observed in these changes among the 3 tertiles. The edema index decreased over the 1-year PD period. The high TA-RRF tertile was associated with a lower edema index. Although there was no statistical significance, the increase in fat mass/lean mass ratio (FM/LM) attenuated as the grade of TA-RRF tertile increased. The increase in fat mass index was similar to the trend in FM/LM.

CONCLUSION

TA-RRF was associated with an increase in total lean mass and a decrease in edema index.

Effect of frequent hemodialysis on residual kidney function

Frequent hemodialysis can alter volume status, blood pressure, and the concentration of osmotically active solutes, each of which might affect residual kidney function (RKF). In the Frequent Hemodialysis Network Daily and Nocturnal Trials, we examined the effects of assignment to six compared with three-times-per-week hemodialysis on follow-up RKF. In both trials, baseline RKF was inversely correlated with number of years since onset of ESRD. In the Nocturnal Trial, 63 participants had non-zero RKF at baseline (mean urine volume 0.76 liter/day, urea clearance 2.3 ml/min, and creatinine clearance 4.7 ml/min). In those assigned to frequent nocturnal dialysis, these indices were all significantly lower at month 4 and were mostly so at month 12 compared with controls. In the frequent dialysis group, urine volume had declined to zero in 52% and 67% of patients at months 4 and 12, respectively, compared with 18% and 36% in controls. In the Daily Trial, 83 patients had non-zero RKF at baseline (mean urine volume 0.43 liter/day, urea clearance 1.2 ml/min, and creatinine clearance 2.7 ml/min). Here, treatment assignment did not significantly influence follow-up levels of the measured indices, although the range in baseline RKF was narrower, potentially limiting power to detect differences. Thus, frequent nocturnal hemodialysis appears to promote a more rapid loss of RKF, the mechanism of which remains to be determined. Whether RKF also declines with frequent daily treatment could not be determined.

Effects of residual renal function on left ventricle and analysis of related factors in patients with hemodialysis

BACKGROUND

Left ventricular hypertrophy (LVH) and systolic dysfunction would predict the mortality of patients undergoing maintenance hemodialysis. The cause of LVH is usually related to the increase of total peripheral vascular resistance and overloading volume. The presence of residual diuresis enables greater control of the volume. This study evaluated the effects of residual renal function (RRF) on the left ventricle and analyzed the related factors involved in hemodialysis patients.

METHODS

A total of 59 hemodialysis patients were classified into two groups. The patients in the RRF (RRF+) group had a urine volume greater than 200 mL/24 h, and the patients in the non-RRF (RRF-) group had a urine volume less than 200 mL/24 h. B-type natriuretic peptide (BNP), blood total homocysteine (tHcy), and blood biochemical indexes were determined for the patients in both groups. Echocardiography and Doppler tests were performed to determine the cardiac indexes.

RESULTS

LVH and systolic dysfunction in the RRF+ group were less severe than those in the RRF- group. The concentration of tHcy and BNP in patients with RRF was decreased in comparison with those without RRF. The concentration of tHcy and BNP was positively correlated with the residual diuresis.

CONCLUSIONS

There were distinct ventricular geometric patterns and different functional performances between RRF+ and RRF- groups. The presence of residual diuresis had a beneficial effect on the left ventricular function in hemodialysis patients.

Elderly dialysis patients: analysis of factors affecting long-term survival in 4-year prospective observation

Purpose

To assess factors influencing the long-term survival of elderly dialysis patients.

Methods

The study group consisted of 51 prevalent dialysis patients aged over 70 years (32 F and 19 M, all caucasians), who had been on a chronic hemodialysis (27) or peritoneal dialysis program (24) for at least 2 months; median age was 77 years, median time on dialysis before inclusion was 16 months, and median residual diuresis was 600 ml. The patients were prospectively followed up to 4 years, and an analysis of factors affecting survival was performed.

Results

Thirteen patients from the initial cohort of 51 (25.5 %) survived the whole 48-month observation period: 10 HD patients (37 %) and 3 PD patients (12.5 %). Annual mortality rate was 28.2 %: 37.4 % on PD vs. 20.9 % on HD. The dialysis modality had a significant impact on patients’ survival (p = 0.049; Cox F-test). The independent mortality risk factors in the Cox proportional hazard regression model were higher plasma pro-atrial natriuretic peptide (pro-ANP) (p = 0.006), lower residual diuresis (p = 0.048), and lower systolic blood pressure (BP) value (p = 0.039).

Conclusions

Paramount for the survival of the elderly on dialysis is adequate extracellular volume control. Residual renal function is a protective factor for the survival of elderly HD patients. This observation is novel, not previously reported in an elderly dialysis population.

Dialysis type may predict carotid intima media thickness and plaque presence in end-stage renal disease patients

INTRODUCTION

Carotid intima media thickness (CIMT) and carotid plaques (CP) were shown to be independent predictors of mortality in end-stage renal disease (ESRD) patients. In this study, the authors aimed to compare the two dialysis modalities for CIMT and CP presence (CPP).

METHODS

ESRD patients who had been on the same renal replacement therapy for at least 24 months were selected. CIMT, CPP, known risk factors, and laboratory parameters for atherosclerosis were determined for each patient.

RESULTS

A total of 77 hemodialysis (HD) patients (68% male, 47.6±17.0 years), 61 continuous ambulatory peritoneal dialysis (CAPD) patients (51% male, 45.3±13.9 years), and 36 age- and sex-matched controls (61% male, 43.3±10.6 years) were included. The mean CIMT (m-CIMT) were 0.99±0.24, 0.86±0.22, and 0.60±0.13 mm in the HD, CAPD, and control groups, respectively (HD vs. CAPD, P=0.001; HD vs. control, P<0.001; and CAPD vs. control, P<0.001). The CPP occurred more frequently in the HD group compared to the CAPD group (64% vs. 39%, respectively, P=0.004). The backward linear and logistic regression analysis of potential confounders revealed that both m-CIMT and CPP was independently associated with dialysis type (beta=0.249, P=0.008; and odds ratio [OR]=4.11, 95% CI, 1.72 to 6.73, P=0.015, respectively).

CONCLUSION

The authors have shown that dialysis type may be an independent predictor of m-CIMT and CPP in long-term ESRD patients.

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.