Comparison of combined urea and creatinine clearance and prediction equations as measures of residual renal function when GFR is low

Average creatinine-urea clearance: revival of an old analytical technique?

Background

Creatinine-based equations such as the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) are recommended for estimating glomerular filtration rate (eGFR) in clinical practice, but have reduced performance in advanced stages of chronic kidney disease. However, only rarely studies have evaluated the performance of eGFR by measuring the average of the urinary clearances of creatinine and urea (mCl_UN-cr) compared with the eGFR equations.

Methods

This cross-sectional study evaluated the usefulness of mCl_UN-cr in a population of 855 participants who performed a GFR measurement by urinary inulin clearance. The performance of mCl_UN-cr was compared with those of CKD-EPI 2009 and CKD-EPI 2021, considering three criteria: bias, precision and accuracy.

Results

In the whole sample, the mCl_UN-cr performed similarly to CKD-EPI equations (2009 and 2021) [precision: 11.5 (95% CI 10.5; 12.5) vs 19.0 (95% CI 17.2; 20.1) and 19.1 (95% CI 17.4; 20.4), and accuracy P₃₀: 97.0 (95% CI 95.8; 98.0) vs 82.0 (95% CI 79.2; 84.4) and 77.2 (95% CI 74.5; 80.0)]. The CKD-EPI equations (2009 and 2021) had the best performance when mGFR was >60 mL/min/1.73 m². In contrast, the mCl_UN-cr performed better than others with lowest mGFR values, more noticeable when mGFR was <60 mL/min/1.73 m².

Conclusions

The study described the best performance of mCl_UN-cr at GFR levels below 60 mL/min/1.73 m² and a satisfactory result in the overall cohort. The findings point to a role of this tool, especially for estimating GFR in chronic kidney disease patients in developing countries, when reference measurement of GFR is not available.

Home-based aerobic exercise and resistance training for severe chronic kidney disease: a randomized controlled trial

BACKGROUND

The potential effects of aerobic and resistance training in patients with severe chronic kidney disease (CKD) are not fully elucidated. This study investigated the effects of a home-based exercise programme on physical functioning and health-related quality of life (HRQOL) in patients with Stage 4 CKD, equivalent to estimated glomerular filtration rate of 15-30 mL/min/1.73 m² .

METHODS

Forty-six patients with Stage 4 CKD (median age, 73 years; 33 men) were randomly assigned to exercise (n = 23) and control (n = 23) groups. Exercise group patients performed aerobic exercise at 40-60% peak heart rate thrice weekly and resistance training at 70% of one-repetition maximum twice weekly at home for 6 months. Control patients received no specific intervention. Primary outcomes were distance in incremental shuttle walking test and HRQOL assessed using the Kidney Disease Quality of Life-Short Form questionnaire. Secondary outcomes included kidney function assessed with combined urea and creatinine clearance, urinary biomarkers, and anthropometric and biochemical parameters associated with CKD.

RESULTS

Improvement in incremental shuttle walking test was significantly greater in the exercise group compared with controls (39.4 ± 54.6 vs. -21.3 ± 46.1; P < 0.001). Among Kidney Disease Quality of Life domains, significant mean differences were observed between the exercise group and the control group in work status, quality of social interaction, and kidney disease component summary outcomes (12.76 ± 5.76, P = 0.03; 5.97 ± 2.59, P = 0.03; and 4.81 ± 1.71, P = 0.007, respectively). There were greater reductions in natural log (ln)-transformed urinary excretion of liver-type fatty acid-binding protein, ln serum C-reactive protein, and acylcarnitine to free carnitine ratio in the exercise group compared with controls, with significant between-group differences of -0.579 ± 0.217 (P = 0.008), -1.13 ± 0.35 (P = 0.003), and -0. 058 ± 0.024 (P = 0.01), respectively.

CONCLUSIONS

Our 6 month home-based exercise programme improved aerobic capacity and HRQOL in patients with Stage 4 CKD, with possible beneficial effects on kidney function and CKD-related parameters.

Impaired Tubular Secretion of Organic Solutes in Advanced Chronic Kidney Disease

BACKGROUND

The clearance of solutes removed by tubular secretion may be altered out of proportion to the GFR in CKD. Recent studies have described considerable variability in the secretory clearance of waste solutes relative to the GFR in patients with CKD.

METHODS

To test the hypothesis that secretory clearance relative to GFR is reduced in patients approaching dialysis, we used metabolomic analysis to identify solutes in simultaneous urine and plasma samples from 16 patients with CKD and an eGFR of 7±2 ml/min per 1.73 m2 and 16 control participants. Fractional clearances were calculated as the ratios of urine to plasma levels of each solute relative to those of creatinine and urea in patients with CKD and to those of creatinine in controls.

RESULTS

Metabolomic analysis identified 39 secreted solutes with fractional clearance >3.0 in control participants. Fractional clearance values in patients with CKD were reduced on average to 65%±27% of those in controls. These values were significantly lower for 18 of 39 individual solutes and significantly higher for only one. Assays of the secreted anions phenylacetyl glutamine, p-cresol sulfate, indoxyl sulfate, and hippurate confirmed variable impairment of secretory clearances in advanced CKD. Fractional clearances were markedly reduced for phenylacetylglutamine (4.2±0.6 for controls versus 2.3±0.6 for patients with CKD; P<0.001), p-cresol sulfate (8.6±2.6 for controls versus 4.1±1.5 for patients with CKD; P<0.001), and indoxyl sulfate (23.0±7.3 versus 7.5±2.8; P<0.001) but not for hippurate (10.2±3.8 versus 8.4±2.6; P=0.13).

CONCLUSIONS

Secretory clearances for many solutes are reduced more than the GFR in advanced CKD. Impaired secretion of these solutes might contribute to uremic symptoms as patients approach dialysis.

Intensive Hemodiafiltration Successfully Removes Ganciclovir Overdose and Largely Exceeds Reported Elimination During Hemodialysis-A Case Report and Review of the Literature

We present the case of a kidney transplant patient (Cockroft-Gault estimated creatinine clearance 14 ml/min) who was inadvertently eight-fold overdosed with a single dose of 500 mg intravenous ganciclovir. To prevent the immunosuppressed patient from being exposed to severe risks of prolonged ganciclovir overdosing, including potentially fatal bone marrow suppression and severe neurotoxicity, the patient was treated with hemodiafiltration (HDF) to enhance drug elimination. Since the product label reports a 50% decrease of ganciclovir plasma concentrations after intermittent hemodialysis (HD), two HDF sessions were considered necessary to achieve a ≥75% elimination of the drug by precaution, despite targeted intense HDF prescription. Ganciclovir plasma concentration data were obtained during both HDF sessions and were analyzed retrospectively. Pharmacokinetic analysis revealed that prescribed HDF successfully decreased drug plasma concentrations by ≥90%. This ganciclovir reduction ratio matched the urea reduction ratio achieved (≥92%). Model-based assessment of ganciclovir dialysis clearance (estimated to be 445 ml/min), accounting for its two-compartmental kinetics, was higher than urea dialysis clearance (estimated to be 310 ml/min). This suggests potential relevant accumulation of ganciclovir into blood cells, at least in this patient after overdosing. The amount (fraction) of drug removed by 1st HDF was estimated to 269 mg (93% of total amount of 288 mg eliminated during the 1st HDF session; estimated amount in the body prior to 1st HDF: 380 mg). A literature review was performed to summarize and systematically compare available information on ganciclovir elimination during intermittent renal replacement therapy. In conclusion, the high ganciclovir HDF clearance measured in our patient largely exceeded previously reported elimination during HD, meaning that HDF prescription was highly efficient in the present case, and that a second HDF session might not have been necessary. This finding may be considered to guide renal replacement therapy in the scope of drug overdosing. It may also be evaluated for ganciclovir dose adjustment in patients on chronic HD or HDF with high small solute clearance, since a strong correlation between ganciclovir and urea elimination efficiency was observed.

Renoprotective effects of renin-angiotensin system inhibitor combined with calcium channel blocker or diuretic in hypertensive patients: A PRISMA-compliant meta-analysis

OBJECTIVES

To conduct a meta-analysis of studies comparing the renoprotective effects of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACEI/ARB) combined with either calcium channel blocker (CCB) or diuretic, but not both, in hypertensive patients.

DATA SOURCES

Pubmed, Embase, Medline, and Cochrane databases were searched to identify randomized controlled trials (RCTs) of blood pressure lowering treatments in patients with hypertension.

STUDY SELECTION

RCTs comparing the renoprotective effects of ACEI/ARB plus CCB with ACEI/ARB plus diuretic in hypertensive patients, with at least one of the following reported outcomes: urinary protein, estimated glomerular filtration rate/creatinine clearance (eGFR/CrCl), or serum creatinine.

RESULTS

Based on 14 RCTs with 18,125 patients, statistically significant benefits were found in ACEI/ARB plus CCB for maintaining eGFR/CrCl (standardized mean difference [SMD] = 0.36; 95% confidence interval [CI]: 0.20-0.53; P < 0.001), serum creatinine reduction (mean difference [MD] = -0.05 mg/dL; 95% CI: -0.07 to -0.03; P < 0.001). However, no statistical differences were found between the 2 therapeutic strategies in terms of urinary protein (MD = 7.48%; 95% CI: -6.13% to 21.08%; P = 0.28; I = 92%).

CONCLUSIONS

This meta-analysis concluded that ACEI/ARB plus CCB have a stronger effect on the maintenance of renal function in patients with hypertension than ACEI/ARB plus diuretic.

Characteristics of urinary and serum soluble Klotho protein in patients with different degrees of chronic kidney disease

Background

Klotho is a single-pass transmembrane protein, which appears to be implicated in aging. The purpose of the present study was to characterize the relationship between the soluble Klotho level and renal function in patients with various degrees of chronic kidney disease (CKD).

Methods

The levels of soluble Klotho in the serum and urine obtained from one hundred thirty-one CKD patients were determined by a sandwich enzyme-linked immunosorbent assay system.

Results

The amount of urinary excreted Klotho during the 24 hr period ranged from 1.6 to 5178 ng/day (median 427 ng/day; interquartile range [IR] 56.8-1293.1), and the serum Klotho concentration ranged from 163.9 to 2123.7 pg/ml (median 759.7 pg/ml; IR 579.5-1069.1). The estimated glomerular filtration rate (eGFR) was significantly correlated with the log-transformed values of the amount of 24 hr urinary excreted Klotho (r = 0.407, p < 0.01) and the serum Klotho levels (r = 0.232, p < 0.01). However, a stepwise multiple regression analysis identified eGFR to be a variable independently associated only with the log-transformed value of the amount of 24-hr urinary excreted Klotho but not with the log-transformed serum Klotho concentration. Despite the strong correlation between random urine protein-to-creatinine ratio and the 24 hr urinary protein excretion (r = 0.834, p < 0.01), a moderate linear association was observed between the log-transformed value of the amount of 24 hr urinary excreted Klotho and that of the urinary Klotho-to-creatinine ratio (Klotho/Cr) in random urine specimens (r = 0.726, p < 0.01).

Conclusions

The amount of urinary Klotho, rather than the serum Klotho levels, should be linked to the magnitude of the functioning nephrons in CKD patients. The use of random urine Klotho/Cr as a surrogate for the amount of 24-hr urinary excreted Klotho needs to be evaluated more carefully.

'Ideal criteria' for starting chronic hemodialysis: numbers, symptoms or an alerting 'traffic light' system?

A definite criteria for starting chronic hemodialysis treatment is still lacking even after 50 years of regular hemodialysis treatment. Although none of the current guidelines have designated a certain glomerular filtration rate (GFR) level to start hemodialysis, most favor an 'earlier' start after GFR falls below 15 ml/min. Hence, since mid-1990s, more patients have initiated dialysis on higher GFR levels. Most of the observational data and one randomized trial, however, failed to find any benefit, but even harm, from an earlier start in various patient populations including the healthiest groups. This paper has reviewed the available evidence and criticized the use of only 'GFR level' in the absence of a validated method in end-stage kidney disease patients. A new patient scoring system mimicking traffic lights was proposed in which patients were placed into green, yellow or red zones for deciding the ideal time to start hemodialysis. This scoring system should include not only validated GFR criteria but also a wide set of demographic and clinical parameters.

Montmorillonite adsorbs creatinine and accelerates creatinine excretion from the intestine

Objectives

This study aims to evaluate the sorption by montmorillonite of creatinine and the accelerating effect of montmorillonite on creatinine excretion from the intestine.

Methods

The sorption of montmorillonite was observed in vitro. Also, rat intestinal tract and blood vessels were perfused circularly with perfusate with or without creatinine, respectively, to study the promotion of creatinine diffusion from the blood vessel to the intestine and the inhibition of creatinine absorption in the intestinal tract. The effect of decreasing the serum concentration of creatinine was studied in an acute hypercreatininaemia mouse model. The concentration of creatinine was determined by the basic picric acid method.

Key findings

Montmorillonite adsorbed creatinine markedly in the simulated intestinal solution in a concentration-dependent manner. The sorption–time curve of montmorillonite with creatinine showed that the sorption was fast. The adsorption rate reached a maximum in 10 min. The pH of the solution influenced the sorption, the rate of which was higher at a low pH than at a high pH. Creatinine could diffuse from the blood vessel to the intestine and was reabsorbed in the intestine. Montmorillonite promoted the diffusion and inhibited the absorption. Montmorillonite decreased the serum creatinine level of hypercreatininaemia mice prepared by injecting creatinine intraperitoneally.

Conclusions

Montmorillonite adsorbs creatinine and accelerates its excretion from the intestine.

Renal effects of plant-derived oleanolic acid in streptozotocin-induced diabetic rats

Previous studies from our laboratories indicate that the anti-diabetic effects of Syzygium cordatum (Hochst.) [Myrtaceae] leaf extract in streptozotocin-induced diabetic rats may be attributed in part to mixtures of triterpenes, oleanolic acid (3ss-hydroxy-olea-12-en-28-oic acid, OA) and ursolic acid (3ss -hydroxyl-urs-12-en-28-oic acid, UA). For the bioactive compounds to have potential in diabetes management, they should alleviate or prevent complications of diabetes mellitus, kidney function, and cardiovascular disorders. This study was, therefore, designed to assess whether S. cordatum leaf derived OA influenced renal function evaluated by the ability to increase urinary Na(+) outputs parameters and creatinine clearance (Ccr) of streptozotocin (STZ)-induced diabetic rats. Extraction and fractionation of S. cordatum powdered leaf ethyl acetate-solubles (EAS) yielded mixtures of OA/UA and methyl maslinate/methyl corosolate. Recrystallization of OA/UA mixture using ethanol afforded OA, the structure of which was confirmed by NMR spectroscopy ((1)H & (13)C). Acute effects of OA on kidney function and mean arterial blood pressure (MAP) were investigated in anesthetized rats challenged with hypotonic saline after a 3.5-h equilibration for 4h of 1 h control, 1.5 h treatment, and 1.5 h recovery periods. OA was added to the infusate during the treatment period. Chronic effects of OA were studied in individually caged rats treated twice daily with OA (60 mg/kg, p.o.) for five weeks. By comparison with respective control animals administration, OA significantly increased Na(+) excretion rates of non-diabetic and STZ-induced diabetic rats without affecting urine flow, K(+) and Cl(-) rates. At the end of five weeks, OA treatment significantly (p < 0.05) increased Ccr in non-diabetic (2.88 +/- 0.14 vs. 3.71 +/- 0.30 ml/min) and STZ-diabetic rats (1.81 +/- 0.32 vs. 3.07 +/- 0.16 ml/min) with concomitant reduction of plasma creatinine concentration (n = 6 in all groups). OA also caused significant decreases in MAP in non-diabetic and STZ-induced diabetic rats. These findings suggest that OA may have beneficial effects on some processes associated with renal derangement of STZ-induced diabetic rats.

Is maximum conservative management an equivalent treatment option to dialysis for elderly patients with significant comorbid disease?

BACKGROUND AND OBJECTIVES

There is ongoing growth of elderly populations with ESRD in Western Europe and North America. In our center, we offer an alternative care pathway of 'maximum conservative management' (MCM) to patients who elect not to start dialysis, often because of a heavy burden of comorbid illness and advanced age. The objective of our study was to compare clinical outcomes for patients who had ESRD and chose either MCM or renal replacement therapy (RRT).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This is an observational study of a single-center cohort in the United Kingdom that evaluating 202 elderly (> or =70 yr) patients who had ESRD and had chosen either MCM (n = 29) or RRT (n = 173). We report survival, hospitalization rates, and location of death for this cohort. Survival was measured from a standardized 'threshold' estimated GFR of 10.8 ml/min per 1.73 m(2).

RESULTS

Median survival, including the first 90 d, was 37.8 mo (range 0 to 106 mo) for RRT patients and 13.9 mo (range 2 to 44) for MCM patients (P < 0.01). RRT patients had higher rates of hospitalization (0.069 [95% confidence interval (CI) 0.068 to 0.070]) versus 0.043 [95% CI 0.040 to 0.047] hospital days/patient-days survived) compared with MCM patients. MCM patients were significantly more likely to die at home or in a hospice (odds ratio 4.15; 95% CI 1.67 to 10.25). A survey of the literature describing elderly ESRD outcomes is also presented.

CONCLUSIONS

Dialysis prolongs survival for elderly patients who have ESRD with significant comorbidity by approximately 2 yr; however, patients who choose MCM can survive a substantial length of time, achieving similar numbers of hospital-free days to patients who choose hemodialysis.

[Investigation of renal function in liver transplant patients: MDRD or Cockroft-Gault?]

Both acute and chronic liver disease have an effect on renal function. After liver transplantation we have to pay attention to the further loss of function because of applied calcineurin inhibitor treatment. It has nephrotoxic side-effect, so the investigation of renal function is converted into an important mission in liver transplant patients. In our study we compared the results between formulas which use serum creatinine: MDRD, which use albumin, too, has effectively other values than the Cockroft-Gault. We compared the two formulas in a retrospective analysis, in 187 patients at a stated time (before operation, after operation, within 1 week, 1 month). We got higher GFR at each date with Cockroft-Gault; mean differences: 19.56%, 17.33%, 37.18% and 28.8%. In the range of 15-60 ml/min GFR, we found nearly twice as many patients by use of MDRD than by use of Cockroft-Gault. Median with MDRD: 79 ml/min, 65.1 ml/min, 52 ml/min, 49.5 ml/min; median with Cockroft-Gault: 93.8 ml/min, 78 ml/min, 70.1 ml/min, 69.4 ml/min, all are significant ( p < 0.001). Many previous studies have already compared the two formulas in end stage kidney disease. On the basis of these studies, MDRD is suitable also under 30 ml/min GFR, but Cockroft-Gault formula approached real GFR measured with isotope methods only above this value. We got the similar conclusion in the examined patient group. It can be stated that MDRD is more suitable to determine renal function in liver transplant patients.