Residual Kidney Function in Hemodialyzed Patients and Related Factors

Measuring residual renal function in dialysis patients: can we dispense with 24-hour urine collections?

Serum Uromodulin and All-Cause Mortality in Peritoneal Dialysis Patients: A Chinese Cohort Study

Residual native kidney function confers health benefits in patients on dialysis. It can facilitate control of extracellular volume and inorganic ion concentrations. Residual kidney function can also limit the accumulation of uremic solutes. This study assessed whether lower plasma concentrations of uremic solutes were associated with residual kidney function in pediatric patients on peritoneal dialysis. Samples were analyzed from 29 pediatric patients on peritoneal dialysis, including 13 without residual kidney function and ten with residual kidney function. Metabolomic analysis by untargeted mass spectrometry compared plasma solute levels in patients with and without residual kidney function. Dialytic and residual clearances of selected solutes were also measured by assays using chemical standards. Metabolomic analysis showed that plasma levels of 256 uremic solutes in patients with residual kidney function averaged 64% (interquartile range, 51%-81%) of the values in patients without residual kidney function who had similar total Kt/Vurea. The plasma levels were significantly lower for 59 of the 256 solutes in the patients with residual kidney function and significantly higher for none. Assays using chemical standards showed that residual kidney function provides a higher portion of the total clearance for nonurea solutes than it does for urea. Concentrations of many uremic solutes are lower in patients on peritoneal dialysis with residual kidney function than in those without residual kidney function receiving similar treatment as assessed by Kt/Vurea.

This study aimed to investigate whether residual kidney function (RKF) influences perioperative hemodynamic stability in hemodialysis patients. Although anesthesiologists have had the clinical impression that RKF contributes to more stable blood pressure during induction of general anesthesia, this association has not been demonstrated. We hypothesized that RKF was associated with less hypotension at induction. We conducted a single-center retrospective study of hemodialysis patients undergoing elective surgery under general anesthesia. RKF was defined as urine output ≥ 100mL/day. The primary outcome was the lowest systolic blood pressure (SBP) during induction. Propensity score matching was performed. Independent predictors of hypotension were identified using multivariable logistic regression. Of 1,086 patients screened, 882 were analyzed (RKF + 335; RKF- 527). After matching, 160 patients were included in each group. In the matched cohort, the lowest SBP was higher in the RKF + group (111 ± 32 vs. 105 ± 30mmHg; p = 0.044). In the full cohort, both the lowest SBP (112 ± 30 vs. 103 ± 29mmHg; p < 0.001) and the decrease (28 ± 33 vs. 37 ± 31mmHg; p < 0.001) were more favorable in the RKF + group, with lower phenylephrine use (0.09 ± 0.19 vs. 0.16 ± 0.35mg; p = 0.001). Logistic regression confirmed RKF, surgery type, and preoperative SBP as independent predictors. RKF was associated with higher SBP at induction of general anesthesia, independent of anesthetic and vasopressor doses. Preoperative assessment of RKF may help identify dialysis patients at risk of induction-related hypotension.

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. 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. 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 (Ptrend < 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. 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.

Let us give twice-weekly hemodialysis a chance: revisiting the taboo.

Understanding of changes in water compartments during hemodialysis (HD) is an important part of ensuring the effectiveness of the procedure and minimizing both intra- and post-dialysis complications.&#x0D; The purpose of our study was to investigate the direction of changes in water sectors in patients with CKD 5D with preserved residual kidney function (RKF) and without RKF.&#x0D; Methods. Prospective observational study enrolled 88 hemodialysis (HD) patients. All patients performed laboratory examinations and measurements of water balance using the BCM monitor before HD, hourly after the start, and 30 minutes after the end of the session. Depending on the presence of residual kidney function, patients were divided into two groups. The first group with RKF included 52 patients, the second - without RKF - 36.&#x0D; Results. Analysis of water balance parameters allowed to conclude that 26 patients (26.13%) were hyperhydrated (OH/ECW above 15%), including 13 (36,11%) in the group without RKF and 10 (19,2%) - in the group with the preserved RKF. There was no statistically significant difference in the groups. When comparing baseline values between groups of patients, it was found that in the group with preserved RKF the albumin level was significantly higher at 8.94% (p&lt;0.05), levels of phosphorus and potassium were lower by 18.27% and 20.24%, respectively. There was no statistically significant difference between other clinical parameters in the groups. Subsequent analysis of the water balance indicators allowed establishing a reliable positive correlation between the level of ultrafiltration (UV) and total body water (TBW). The higher the UV level, the higher the ECW (p &lt; 0.05). Similar results were obtained when analyzing the relationship between extracellular fluid (ECW) and UV (p &lt; 0,001). As a result of the correlation analysis between the level of UV and diuresis, the mean inverse correlation relationship is shown, which shows - the lower the diuresis, the higher the level of ultrafiltration (p &lt; 0,001). During HD the TBW (ΔTBW = 1.5 ± 1.8) and ECW (ΔECW = 1.92 ± 0.85) progressively decrease, the ICW compartment is practically unchanged (ΔICW = -0.17 ± 0.89). In patients with preserved RKF the change in ECW is significantly lower comparatively with the group without RKF (p &lt;0.05).&#x0D; Conclusions. Obtained data indicate that the clinical evaluation of hyperhydration is not always adequate. The obtained results confirm the fact that the presence of RKF provides better phosphorus and potassium levels control in patients with CKD. During HD the removal of fluid occurs directly from the extracellular space, in the group with the RKF to a lesser extent, indicating that the presence of diuresis provides a lower volume of OH, TBW, ECW before HD session, and therefore the level of ultrafiltration appears to be less. Thus the RKF also provides better control of water balance. The results of the dynamics of water sector changes during HD can be used to assess the refilling in the future.

Residual kidney function is a major prognosis factor in patients with end-stage renal disease under hemodialysis or peritoneal dialysis. Advances in later years promoted residual kidney function protection as an adequacy target and the advocacy of incremental dialysis, utilizing its assessment as a parameter of individualized dialysis schedules. Glomerular filtration rate measurement is only a dimension of kidney function neglecting the share of tubular function, with several dialytic limitations. The need for interdialytic urine collections to quantify residual kidney function, by the mean of urea and creatinine clearances, is cumbersome and prone to errors in dialysis patients. This review will approach residual kidney function estimation without urine collection, mainly with biomarkers such as cystatin C, beta-2 microglobulin, and beta-trace protein, as well as the behavior of these molecules on various dialysis modalities, their non-renal determinants, and its potential use for patient risk stratification. Multi-frequency bioimpedance analysis is also described as a promising approach to estimate residual kidney function, being an opportunity to highlight the relevant link between volume balance and diuresis. We conclude that standard glomerular filtration rate estimation formulas are not sufficiently accurate for residual kidney function assessment. There is a need for innovative tools that consider glomerular and interstitial function to be implement in clinical practice, therefore the new equations already developed and approached in this review should be validated in larger cohorts.

Angiotensin-converting enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) are widely used in peritoneal dialysis (PD) patients, yet controversy exists about their impact on residual kidney function. This review aimed to evaluate the benefits and harms of ACEis and ARBs for preserving residual kidney function in PD patients. The Cochrane Renal Group's specialised register, Cochrane Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE (OvidSP interface), Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI) and other resources were searched by applying a prespecified comprehensive search strategy. Date of last search: 01 May 2014. Randomised controlled trials (RCTs) and quasi-RCTs comparing ACEis or ARBs with placebo, other antihypertensive drugs or each other in PD patients were included. Screening, selection, data extraction and quality assessments for each retrieved article were carried out by two authors using standardised forms. Authors were contacted when published data were incomplete. Statistical analyses were performed using the random effects model and results expressed as risk ratio (RR) with 95% confidence intervals (CI). Heterogeneity among studies was explored using the Cochran Q statistic and the I² test, subgroup analyses and random effects meta-regression. Six open-label studies (257 patients) were identified. One study compared ACEi with other antihypertensive drugs, three compared ARBs with other antihypertensive drugs, and two studies compared an ARB with an ACEi. Long-term use (≥ 12 months) of an ARB showed significantly benefit of preserving residual kidney function in continuous ambulatory PD (CAPD) patients (MD 1.11 mL/min/1.73 m², 95% CI 0.38 to 1.83), although there was no significant benefit when an ARB were used short-term (≤ six months). One study showed that compared with other antihypertensive drugs, long-term use (12 months) of the ACEi ramipril showed a significant reduction in the decline of residual kidney function in patients on CAPD (MD -0.93 mL/min/1.73m², 95% CI -0.75 to -0.11), and delayed the progression to complete anuria (RR 0.64, 95% CI 0.41 to 0.99). There was no significant difference in serum potassium, urinary protein excretion, Kt/V, weekly creatinine clearance and blood pressure for ARBs versus other antihypertensive drugs. Compared with other antihypertensive drugs, ramipril showed no difference in mortality and cardiovascular events. Compared with an ACEi, ARBs did not show any difference in residual kidney function.The selection bias assessment was low in four studies and unclear in two. Five studies were open-label; however the primary outcome (residual kidney function) was obtained objectively from laboratory tests, and were not likely to be influenced by the lack of blinding. Reporting bias was unclear in all six studies. Compared with other antihypertensive drugs, long-term use (≥ 12 months) of ACEis or ARBs showed additional benefits of preserving residual kidney function in CAPD patients. There was no significant difference on residual kidney function preservation between ARBs and ACEis. However, limited by the small number of RCTs enrolling small number of participants, there is currently insufficient evidence to support the use of an ACEi or an ARB as first line antihypertensive therapy in PD patients.

The ESHOL study: hemodiafiltration improves survival—but how?

Background Most patients on hemodialysis are treated thrice weekly even if they have residual kidney function, in part because uncertainty remains as to how residual function should be valued and incorporated into the dialysis prescription. Recent guidelines, however, have increased the weight assigned to residual function and thus reduced the treatment time required when it is present. Increasing the weight assigned to residual function may be justified by knowledge that the native kidney performs functions not replicated by dialysis, including solute removal by secretion. This study tested whether plasma concentrations of secreted solutes are as well controlled in patients with residual function on twice weekly hemodialysis as in anuric patients on thrice weekly hemodialysis.Methods We measured the plasma concentration and residual clearance, dialytic clearance, and removal rates for urea and the secreted solutes hippurate, phenylacetylglutamine, indoxyl sulfate, and p-cresol sulfate in nine patients on twice weekly hemodialysis and nine patients on thrice weekly hemodialysis.Results Compared with anuric patients on thrice weekly dialysis with the same standard Kt/Vurea, patients on twice weekly hemodialysis had lower hippurate and phenylacetylglutamine concentrations and similar indoxyl sulfate and p-cresol sulfate concentrations. Mathematical modeling revealed that residual secretory function accounted for the observed pattern of solute concentrations.Conclusions Plasma concentrations of secreted solutes can be well controlled by twice weekly hemodialysis in patients with residual kidney function. This result supports further study of residual kidney function value and the inclusion of this function in dialysis adequacy measures.

Development and Validation of Residual Kidney Function Estimating Equations in Dialysis Patients

BackgroundLower blood pressure (BP) levels are linked to a slower decline of kidney function in patients with chronic kidney disease (CKD) without kidney replacement therapy. However, there are limited data on this relation in peritoneal dialysis (PD) patients. Here we evaluated the association of BP levels with the decline of residual kidney function (RKF) in a retrospective cohort study.MethodsWe enrolled 228 patients whose PD was initiated between 1998 and 2014. RKF was measured as the average of creatinine and urea clearance in 24-hr urine collections. We calculated the annual decline rate of RKF by determining the regression line for individual patients. RKF is thought to decline exponentially, and thus we also calculated the annual decline rate of logarithmic scale of RKF (log RKF). We categorized the patients’ BP levels at 3 months after PD initiation (BP3M) into four groups (Optimal, Normal & High normal, Grade 1 hypertension, Grade 2 & 3 hypertension) according to the 2018 European Society of Cardiology and European Society of Hypertension Guidelines for the management of arterial hypertension.ResultsThe unadjusted, age- and sex-adjusted, and multivariable-adjusted decline rate of RKF and log RKF decreased significantly with higher BP3M levels (P for trend <0.01). Compared to those of the Optimal group, the multivariable-adjusted odds ratios (95% confidence interval) for the faster side of the median decline rate of RKF and log RKF were 4.04 (1.24–13.2) and 5.50 (1.58–19.2) in the Grade 2 and 3 hypertension group, respectively (p<0.05).ConclusionsHigher BP levels after PD initiation are associated with a faster decline in RKF among PD patients.

Residual kidney function for patients with chronic kidney disease (CKD) is associated with better quality of life and outcome; thus, strategies should be implemented to preserve kidney function. Among the multiple causes that promote kidney damage, gut dysbiosis due to increased uremic toxin production and endotoxemia need attention. Several strategies have been proposed to modulate the gut microbiota in these patients, and diet has gained increasing attention in recent years since it is the primary driver of gut dysbiosis. In addition, medications and faecal transplantation may be valid strategies. Modifying gut microbiota composition may mitigate chronic kidney damage and preserve residual kidney function. Although various studies have shown the influential role of diet in modulating gut microbiota composition, the effects of this modulation on residual kidney function remain limited. This review discusses the role of gut microbiota metabolism on residual kidney function and vice versa and how we could preserve the residual kidney function by modulating the gut microbiota balance.

Residual kidney function (RKF) contributes to improved survival in hemodialysis (HD) patients. However, it is not clear whether RKF allows a comparable survival rate in patients undergoing twice-weekly HD compared with thrice-weekly HD.We enrolled 685 patients from a prospective multicenter observational cohort. RKF and HD adequacy was monitored regularly over 3-year follow-up. Patients with RKF were divided into groups undergoing twice-weekly HD (n = 113) or thrice-weekly HD (n = 137). Patients without RKF undergoing thrice-weekly HD (n = 435) were included as controls. Fluid balance and dialysis-associated characteristics were followed and clinical outcomes evaluated using all-cause mortality and cardiovascular events (CVE).In patients with RKF, baseline and follow-up RKF were significantly higher in patients undergoing twice-weekly HD than in those undergoing thrice-weekly HD. Total Kt/V urea (dialysis plus residual renal) in patients with RKF undergoing twice-weekly HD was greater than or equal to those in patients with or without RKF undergoing thrice-weekly HD. Compared with patients with RKF undergoing thrice-weekly HD, patients with RKF undergoing twice-weekly HD had no fluid excess, but their normalized protein catabolic rate became lower since 24-month follow up. In multivariable analyses, patients with RKF undergoing twice-weekly HD had a noninferior risk of mortality (hazard ratio [HR], 0.83; 95% confidence interval [95% CI], 0.34–2.01, P = 0.68) and of CVE (HR, 0.60; 95% CI, 0.28–1.29, P = 0.19) compared with patients without RKF undergoing thrice-weekly HD. However, this group showed an independent association with a greater risk of mortality compared with patients with RKF undergoing thrice-weekly HD (HR, 4.20; 95% CI, 1.02–17.32, P = 0.04).In conclusion, patients with RKF undergoing twice-weekly HD had an increased risk of mortality compared with those undergoing thrice-weekly HD. Decisions about twice-weekly HD should consider not only RKF, but also other risk factors such as normalized protein catabolic rate.