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Resumen: Antecedentes y objetivo: El número de personas que inician diálisis por el fracaso del injerto aumenta cada día. La modalidad de diálisis mejor para este tipo de pacientes no está bien definida y la mayoría de ellos son derivados a hemodiálisis (HD). El objetivo de nuestro estudio es evaluar el impacto de la modalidad de diálisis sobre la morbilidad y la mortalidad en individuos trasplantados que inician este procedimiento tras el fracaso del injerto. Material y métodos: Estudio multicéntrico retrospectivo observacional y de cohortes que compara la evolución de los pacientes que inician diálisis tras el fracaso del injerto, desde enero del año 2000 a diciembre del 2013. Un grupo lo hace en diálisis peritoneal (DP) y otro en HD. Se realizó un seguimiento a los pacientes hasta el cambio de técnica de diálisis, retrasplante o fallecimiento. Se analizaron datos antropométicos, comorbilidad, el filtrado glomerular (FG) con el que iniciaban la diálisis, la presencia de un acceso óptimo para esta, la presencia de intolerancia al injerto y el retrasplante. Estudiamos el motivo de los 10 primeros ingresos hospitalarios tras el inicio de la diálisis. Para el análisis estadístico, se tuvo en cuenta la presencia de eventos competitivos que dificultaran la aparición del evento de interés, muerte o ingreso hospitalario. Resultados: Se incluyeron 175 pacientes. En DP 86 y 89 en HD. Los individuos que iniciaron DP eran más jóvenes, tenían menor comorbilidad y lo hacían con FG más bajos que los de HD. El seguimiento medio fue de 34 ± 33 meses, con una mediana de 24 (IQR siete a 50 meses), siendo mayor en los pacientes en HD que en los de DP (35 vs. 18 meses, p = < 0,001). Los factores de riesgo que influyeron en la mortalidad fueron la edad (coeficiente del sub Hazard Ratio [sHR] 1,06 (IC 95%: 1,033 a 1,106, p = 0,000), el uso no óptimo del acceso (sHR 3,00 (IC 95%: 1,507 a 5,982, p = 0,028) y el tipo de diálisis, la DP sHR[DP/HD] 0,36 (IC 95%: 0,148 a 0,890, p = 0,028). Los pacientes en DP tenían menos riesgo de un ingreso hospitalario sHR[DP/HD] 0,52 (IC 95%: 0,369 a 0,743, p = < 0,001) y menos probabilidad de desarrollar una intolerancia al injerto HR 0,307 (IC 95% 0,142 a 0,758, p = 0,009). Conclusiones: Con las limitaciones de un estudio retrospectivo y no randomizado, es la primera vez a nivel nacional que se demuestra que la DP en términos de supervivencia es mejor que la HD cuando fracasa el injerto durante el primer año y medio en diálisis. La presencia de un acceso no óptimo para este procedimiento es un factor de riesgo de mortalidad independiente y modificable. La remisión precoz de los pacientes a las unidades de enfermedad renal crónica avanzada (ERCA) es fundamental para que estos elijan la técnica que más se adapte a sus circunstancias y preparar un acceso óptimo para el inicio de diálisis. Abstract: Background and objective: The number of patients who start dialysis due to graft failure increases every day. The best dialysis modality for this type of patient is not well defined and most patients are referred to HD. The objective of our study is to evaluate the impact of the dialysis modality on morbidity and mortality in transplant patients who start dialysis after graft failure. Material and methods: A multicentre retrospective observation and cohort study was performed to compare the evolution of patients who started dialysis after graft failure from January 2000 to December 2013. One group started on PD and the other on HD. The patients were followed until the change of dialysis technique, retransplantation or death. Anthropometric data, comorbidity, estimated glomerular filtration rate (eGFR) at start of dialysis, the presence of an optimal access for dialysis, the appearance of graft intolerance and retransplantation were analysed. We studied the causes for the first 10 hospital admissions after starting dialysis. For the statistical analysis, the presence of competitive events that hindered the observation of the event of interest, death or hospital admission was analysed. Results: 175 patients were included, 86 in DP and 89 in HD. The patients who started PD were younger, had less comorbidity and started dialysis with lower eGFR than those on HD. The mean follow-up was 34 ± 33 months, with a median of 24 months (IQR 7 - 50 months), Patients on HD had longer follow-up than patients on PD (35 vs. 18 months, p = < 0.001). The mortality risk factors were age sHR 1.06 (95% CI: 1.033 - 1.106, p = 0.000), non-optimal use of access for dialysis sHR 3.00 (95% CI: 1.507 - 5.982, p = 0.028) and the dialysis modality sHR (PD / HD) 0.36 (95% CI: 0.148 - 0.890, p = 0.028). Patients on PD had a lower risk of hospital admission sHR [DP / HD] 0.52 (95% CI: 0.369-0.743, p = < 0.001) and less probability of developing graft intolerance HR 0.307 (95% CI 0.142-0.758, p = 0.009). Conclusions: With the limitations of a retrospective and non-randomized study, it is the first time nationwide that PD shows in terms of survival to be better than HD during the first year and a half after the kidney graft failure. The presence of a non-optimal access for dialysis was an independent and modifiable risk factor for mortality. Early referral of patients to advanced chronic kidney disease units is essential for the patient to choose the technique that best suits their circumstances and to prepare an optimal access for the start of dialysis.

BACKGROUND AND AIMS HFR-Supra (haemodiafiltration with the regeneration of the ultrafiltrate) is a highly biocompatible dialysis technique characterized by an adsorptive resin cartridge with high protein-bound toxin adsorption capacity without removal of albumin, mimicking both glomerular and tubular functions. However, the low-flux dialyzer contained in the second diffusive stage of the HFR Supra system may hamper the removal of large uraemic toxins. This study assessed the large uraemic toxin removal ability of a new HFR system (HFR-H) which combines adsorption such as in HFR-Supra, with a high-efficiency high-flux haemodialysis membrane. METHOD In an open, randomized, cross-over, single-center, controlled study, 16 adult chronic haemodialysis patients were treated by haemodiafiltration with the regeneration of the ultrafiltrate with the HFR-Supra or the HFR-H system. All other dialysis parameters were kept constant in both study arms. All the treatments were delivered with Flexya dialysis monitor (Medtronic) in the middle-week session, lasting 4-h. The reduction rate (RR) of urea, creatinine, phosphate, β2-microglobulin, kappa (κFLC) and lambda (λFLC) free light chains and albumin, was intra-individually compared for the two dialysis types with linear mixed models. RESULTS The RRs for β2-microglobulin, κFLC and λFLC were significantly higher with the HFR-H system than those obtained with HFR-Supra (Figure). There were no significant differences in the RR for urea, creatinine, phosphate, interleukin-6 and albumin. CONCLUSION This study demonstrates that treating patients with an HFR-H instead of an HFR-Supra system significantly increases the elimination of middle and large molecules.

BACKGROUND AND AIMS Chronic kidney disease-associated pruritus (CKD-aP) is a very common symptom in dialysis patients and can significantly limit their quality of life and survival. While the prevalence of CKD-aP in peritoneal dialysis (PD) and in-center hemodialysis (HD) patients has been studied, little data are known for home HD (HHD) patients. The objective of this study was to analyse the prevalence of pruritus in HHD patients, and the factors associated with its presentation, as compared to PD and in-center HD patients. METHOD Cross-sectional, single-center study that included all patients on chronic dialysis treated at our center in November 2021. The patients were divided into three groups according to the dialysis modality (HHD, PD and in-center HD). All the patients answered a validated questionnaire on CKD-aP that evaluated the presence of itching, its intensity, frequency and location; the moment of appearance; the effect on quality of life, emotional state, cognitive function, sexual activity and quality of sleep. Likewise, it was assessed whether they had previously been diagnosed and treated for CKD-aP. The visual analogue scale (VAS) was used to define the intensity of itching as absent (VAS = 0), mild (VAS = 1–2), moderate (VAS = 3–6) or severe (VAS = 7–10). Clinical and analytical variables were compared between the groups, and the factors associated with the presence of pruritus were analysed using binary logistic regression. RESULTS Nighty-nine patients (41% women) were included, with a mean age of 64 ± 15 years and a median stay on dialysis of 57 (IQR: 17–159) months. The proportion of patients on HHD, PD and in-center HD was 20%, 41% and 39%, respectively. A total of 36% of the patients had some degree of pruritus, being mild, moderate, and severe in 8%, 13%, and 13% of the patients, respectively. The prevalence of pruritus and its intensity was similar in all the dialysis modalities (Figure 1). In the logistic regression analysis, the dialysis modality was not associated with presence of CKD-aP. CONCLUSION In our experience, the prevalence and intensity of pruritus was similar in HHD, PD and in-center HD patients. These data suggest that the type of dialysis techniques does not influence CKD-aP prevalence.

BACKGROUND AND AIMS Portable haemodialysis (HD) systems with a low dialysate flow rate in a short frequent schedule have become an attractive option for patients on home HD (HHD). Although these systems have been demonstrated to be effective for removing low weight molecular uraemic toxins, there are few data on their removal ability of higher molecular weight toxins. This study assessed the uraemic toxin removal ability of the portable Physidia S3 Monitor in a short, frequent, 5 days/week, low-dialysate flux HHD versus 3 days/week, in centre online haemodiafiltration (OL-HDF). METHOD In an open, randomized, cross-over, single-centre, controlled, prospective study, 40 adult chronic HD patients were treated by a 2.5-h low flux dialysate HD session or a 4-h post-dilution OL-HDF. All other dialysis parameters including dialyzer (polysulfone high-flux dialyzer NS 1.8, Toray®) were kept constant in both the study arms. The weekly reduction rate (RR) and the weekly eliminated mass into dialysate (EM) of urea, creatinine, phosphate, β2-microglobulin, kappa (κFLC) and lambda (λFLC) free light chains and albumin, were intra-individually compared for the two dialysis types with linear mixed models. RESULTS There were no significant differences in the RR for urea, phosphate, κFLC and albumin, whereas the weekly RRs for creatinine and β2-microglobulin were significantly higher with the Physidia S3 system than those obtained with OL-HDF (Table). Only the λFLC RR was significantly higher with OL-HDF. Similar results were observed when weekly EMs were compared (data not shown). CONCLUSION This study demonstrates that treating patients with low flow dialysate HHD in a short frequent schedule with Physidia S3 system, instead of 3 days/week, in-centre OL-HDF, significantly increases the weekly elimination of β2-microglobulin, enabling an adequate clearance of small and large uraemic toxins.

BACKGROUND AND AIMS The success of peritoneal dialysis (PD) depends on the integrity of the peritoneal membrane. The most common peritoneal functional alteration is an impaired ultrafiltration caused by fast peritoneal solute transfer rate. This situation can be present at start of PD and compromise the durability of the membrane through the stay on PD. If the patient leaves PD for another reason, as in the case of a kidney transplant, it affects the probability of a membrane dysfunction appearance. It is known as a competitive event. The aim of this study was to determine whether baseline peritoneal transport status was a risk factor of mortality and technique failure in a cohort of Spanish PD patients using a statistical competing risk model. METHOD The multicenter retrospective cohort study included adult patients of the Levante Registry PD Work Group in Spain who started PD between February 1993 and June 2020. All patients needed to have a peritoneal equilibration test (PET) performed within the first 6 months after PD start. Patients were followed until technique failure, transplantation, renal function recovery, death, or until September 2020. Peritoneal transport status was considered both as a continuous (D/PCr4h) and as a categorical variable, according to the four groupings of D/PCr values defined by Twardoski. We analysed the effect of peritoneal transport over mortality, peritonitis and technique failure by a competing risk model. Kidney transplantation and renal function recovery were considered competing events. RESULTS A total of 4848 patients were enrolled. Baseline PET measurements were available in 2.307 (47.6%). The median follow-up time was 22.2 months (IQR 11.5–40.5). The main characteristics according to the peritoneal transport status are summarized in Table 1. When peritoneal membrane transport was analysed as a continuous variable, D/PCr was an independent risk factor of technique failure. The hazard ratio subdistribution for technique failure was 1.08 [(1.01; 1.16), P-value = 0.018] for every 0.1 increase in D/P Cr ratio. This effect disappeared when the use of icodextrin was included in the model. Baseline peritoneal transport was not associated with a higher mortality or peritonitis risk. CONCLUSION Basal peritoneal transport rate is an independent risk factor for death-censored technique failure in the Levante DP incident population. The use of icodextrin in these patients seems to mitigate this negative effect and may improve the outcomes in PD in patients with initial fast transport. Conventional methods for survival analysis ignoring the competing events may be inappropriate this cohort of patients.

The number of patients who start dialysis due to graft failure increases every day. The best dialysis modality for this type of patient is not well defined and most patients are referred to HD. The objective of our study is to evaluate the impact of the dialysis modality on morbidity and mortality in transplant patients who start dialysis after graft failure.A multicentre retrospective observation and cohort study was performed to compare the evolution of patients who started dialysis after graft failure from January 2000 to December 2013. One group started on PD and the other on HD. The patients were followed until the change of dialysis technique, retransplantation or death. Anthropometric data, comorbidity, estimated glomerular filtration rate (eGFR) at start of dialysis, the presence of an optimal access for dialysis, the appearance of graft intolerance and retransplantation were analysed. We studied the causes for the first 10 hospital admissions after starting dialysis. For the statistical analysis, the presence of competitive events that hindered the observation of the event of interest, death or hospital admission was analysed.175 patients were included, 86 in DP and 89 in HD. The patients who started PD were younger, had less comorbidity and started dialysis with lower eGFR than those on HD. The mean follow-up was 34 ± 33 months, with a median of 24 months (IQR 7 - 50 months), Patients on HD had longer follow-up than patients on PD (35 vs. 18 months, p =0.001). The mortality risk factors were age sHR 1.06 (95% CI: 1.033 - 1.106, p = 0.000), non-optimal use of access for dialysis sHR 3.00 (95% CI: 1.507 - 5.982, p = 0.028) and the dialysis modality sHR (PD / HD) 0.36 (95% CI: 0.148 - 0.890, p = 0.028). Patients on PD had a lower risk of hospital admission sHR [DP / HD] 0.52 (95% CI: 0.369-0.743, p =0.001) and less probability of developing graft intolerance HR 0.307 (95% CI 0.142-0.758, p = 0.009).With the limitations of a retrospective and non-randomized study, it is the first time nationwide that PD shows in terms of survival to be better than HD during the first year and a half after the kidney graft failure. The presence of a non-optimal access for dialysis was an independent and modifiable risk factor for mortality. Early referral of patients to advanced chronic kidney disease units is essential for the patient to choose the technique that best suits their circumstances and to prepare an optimal access for the start of dialysis.

Background and Aims Dialytic clearance of protein-bound toxins and large middle molecules is poor by diffusive treatment and limited by high-flux hemodialysis (HD) and on-line hemodiafiltration (OL-HDF), and only a few studies have examined how to improve their removal by other extracorporeal strategies. Since 2017, there is a new generation of polymethyl methacrylate (PMMA) membranes that suppress platelet adhesion on the membrane surface improving hemocompatibility and permeability, while also maintaining adsorption properties related to conventional PMMA membranes. Expanded HD (HDx) with medium cut-off (MCO) membranes has also recently been incorporated into clinical practice and may improve the removal of uremic toxins in HD treatments. The aim of this pilot study was to compare the efficacy of a new high-flux PMMA dialyzer (Filtryzer® NF-2.1H) in a post-dilution OL-HDF session with a new MCO membrane (Theranova® 400) in a HDx session. Method In an open, cross-over, single-center, controlled, prospective clinical study, 40 adult stable HD patients were assigned to be treated by post-dilution OL-HDF with the NF-2.1H dialyzer or by HDx with the Theranova 400 dialyzer. All other dialysis parameters, including blood and dialysate flow rates, length of dialysis session, and ultrafiltration rate remained unchanged during both sessions. P-cresyl sulfate (PCS), indoxyl sulfate (IS), and kappa (κ) and lambda( λ) free light chains (FLC) reduction rates were intraindividually compared for the two dialyzer types (primary outcomes). Secondary outcomes included the kt and the reduction ratio of blood urea nitrogen, phosphate and β2 -microglobulin (β 2-m). Results The reduction ratio of protein-bound toxins ranges from 60% to 67%, with no differences between membranes (Figure). PMMA membrane achieved greater FLC reduction ratios than MCO membrane, reaching significance for λFLC (56.6% vs. 77.4%; p < 0.001). Conversely, β2M reduction ratio was slightly but significantly higher with MCO membrane (68.5 vs. 72.1%; p = 0.002). Small molecules removal including urea and phosphate were similar in both groups, achieving an optimal Kt with no differences between groups (61.3±9.2 Vs. 59.7±9.3; p=0.16). Albumin reduction ratio tended to be higher with PMMA membrane without reaching significance (10.1±5.9% Vs. 7.8±12.3%; p=0.17). The mean convective volume achieved with PMMA was 23.5±4.4 L. Conclusion This study suggested that new high-flux PMMA dialyzer in post-dilution OL-HDF mode might achieve better FLC reduction ratios than MCO dyalizer in HDx mode, whereas both techniques may equally remove protein-bound toxins. OL-HDF with new PMMA membranes could be a good dialysis strategy for adding convective transport to the well-known mechanisms of diffusion and absorption previously described with conventional PMMA membranes, enabling an adequate substitution volume.

Background and Aims Short-daily hemodialysis (HD) with low-dialysate volume is an appealing portable dialysis approach for home use. Although this type of HD has proved being effective for the volume control and the clearance of low molecular-weight uremic toxins, limited data are available on the impact on the removal rates of other uremic toxins like β2-microglobulin (β2M) or phosphate (P), whose clearance is limited by sequestration into compartments, poor diffusion, high time-dependency, or protein binding. We evaluated the impact of short-daily HD with slow dialysate flow rate on the removal of solutes of different molecular weights and distribution volumes. Method Single-session and weekly balances of β2M, P, urea, and creatinine were prospectively assessed with total dialysate collection and serum measurements before and after 341 dialysis sessions (mean dialysate volume: 30963 ± 862 mL; mean length of dialysis session: 153 ± 8 min) in 31 stable patients (female; 9, 29 %; mean age: 55.6 ± 13.6 y; dry weight: 74.9 ± 13.3 kg) undergoing short-daily home HD with NxStage cycler, between July 2014 and October 2019. The mean blood flow rate was 365 ± 17 mL/min, whereas the mean dialysate flow rate was 194 ± 12 mL/min. Results Single-session β2M, P, urea, and creatinine removals were 0.138 ± 0.050 g, 0.610 ± 0.161 g, 18.89 ± 6.07 g and 1.07 ± 0.31 g, respectively, whereas the reduction rates (%) were 38.0 ± 13.0, 46.8 ± 8.6, 48.2 ± 7.0 and 46.6 ± 6.6, for β2M, P, urea and creatinine, respectively. The estimated weekly β2M, P, urea and creatinine removals in HDD patients dialyzing 5-6 days per week were comparable with 4-h in-center thrice-weekly on-line hemodiafiltration according to previous studies (Table 1). Conclusion Treating patients with short-daily HD with low-dialysate volume at a 5-6 days per week prescription may achieve an efficient weekly β2M and P removal.

Background Compared with conventional haemodialysis (HD), online haemodiafiltration (OL-HDF) achieves a more efficient removal of uraemic toxins and reduces inflammation, which could favourably affect nutritional status. We evaluate the effect of OL-HDF on body composition and nutritional status in prevalent high-flux HD (HF-HD) patients. Methods In all, 33 adults with chronic kidney disease (CKD) Stage 5 undergoing maintenance HF-HD were assigned to post-dilution OL-HDF (n = 17) or to remain on HF-HD (n = 16, control group) for 12 months. The primary outcome was the change in lean tissue mass (LTM), intracellular water (ICW) and body cell mass (BCM) assessed by multifrequency bioimpedance spectroscopy (BIS) at baseline and 4, 8 and 12 months. The rate of change in these parameters was estimated with linear mixed-effects models. Results Compared with OL-HDF, patients assigned to HF-HD experienced a gradual reduction in LTM, ICW and BCM. These differences reached statistical significance at Month 12, with a relative difference of 7.31 kg [95% confidence interval (CI) 2.50-12.11; P = 0.003], 2.32 L (95% CI 0.63-4.01; P = 0.008) and 5.20 kg (95% CI 1.74-8.66; P = 0.004) for LTM, ICW and BCM, respectively. The normalized protein appearance increased in the OL-HDF group compared with the HF-HD group [0.26 g/kg/day (95% CI 0.05-0.47); P = 0.002], with a relative reduction in high-sensitive C-reactive protein [-13.31 mg/dL (95% CI -24.63 to -1.98); P = 0.02] at Month 12. Conclusions OL-HDF for 1 year compared with HF-HD preserved muscle mass, increased protein intake and reduced the inflammatory state related to uraemia and dialysis, supporting the hypothesis that high convection volume can benefit nutritional status and prevent protein-energy wasting in HD patients.

Although some experimental targets involved in calcium deposition are emerging, no intervention has been described to reliably reverse vascular calcification (VC). We report a case of severe VC regression in a parathyroidectomized patient on hemodialysis over 12-year follow-up, highlighting the use of calcium-free phosphate binders and a 2.5 mEq/L calcium dialysate for reducing calcium loading, despite persistent asymptomatic hypocalcemia occurrences. This case suggests that phosphate-binder choice and calcium dialysate concentration could be influenced by other components of CKD-MBD besides biochemical parameters, such as the presence of VC, so concluding that asymptomatic hypocalcemia may not be as harmful as once supposed, and conferring greater prognostic weight to the presence of VC than to calcium levels. .

AIM: To evaluate thresholds for serum 25(OH)D concentrations in relation to death, kidney progression and hospitalization in non-dialysis chronic kidney disease (CKD) population. METHODS: Four hundred and seventy non-dialysis 3-5 stage CKD patients participating in OSERCE-2 study, a prospective, multicenter, cohort study, were prospectively evaluated and categorized into 3 groups according to 25(OH)D levels at enrollment (less than 20 ng/mL, between 20 and 29 ng/mL, and at or above 30 ng/mL), considering 25(OH)D between 20 and 29 ng/mL as reference group. Association between 25(OH)D levels and death (primary outcome), and time to first hospitalization and renal progression (secondary outcomes) over a 3-year follow-up, were assessed by Kaplan-Meier survival curves and Cox-proportional hazard models. To identify 25(OH)D levels at highest risk for outcomes, receiver operating characteristic (ROC) curves were performed. RESULTS: Over 29 ± 12 mo of follow-up, 46 (10%) patients dead, 156 (33%) showed kidney progression, and 126 (27%) were hospitalized. After multivariate adjustment, 25(OH)D < 20 ng/mL was an independent predictor of all-cause mortality (HR = 2.33; 95%CI: 1.10-4.91; P = 0.027) and kidney progression (HR = 2.46; 95%CI: 1.63-3.71; P < 0.001), whereas the group with 25(OH)D at or above 30 ng/mL did not have a different hazard for outcomes from the reference group. Hospitalization outcomes were predicted by 25(OH) levels (HR = 0.98; 95%CI: 0.96-1.00; P = 0.027) in the unadjusted Cox proportional hazards model, but not after multivariate adjusting. ROC curves identified 25(OH)D levels at highest risk for death, kidney progression, and hospitalization, at 17.4 ng/mL [area under the curve (AUC) = 0.60; 95%CI: 0.52-0.69; P = 0.027], 18.6 ng/mL (AUC = 0.65; 95%CI: 0.60-0.71; P < 0.001), and 19.0 ng/mL (AUC = 0.56; 95%CI: 0.50-0.62; P = 0.048), respectively. CONCLUSION: 25(OH)D < 20 ng/mL was an independent predictor of death and progression in patients with stage 3-5 CKD, with no additional benefits when patients reached the levels at or above 30 ng/mL suggested as optimal by CKD guidelines. Abbott and the Spanish Society of Nephrology