Bioimpedance analysis in patients with chronic kidney disease

Dynamic changes in liver stiffness measurements using transient elastography in hemodialysis patients

Background and Aim

The impact of fluid status changes on liver stiffness measurements (LSM) using transient elastography (TE) in dialysis patients remains unclear. This study aimed to evaluate LSM variations during hemodialysis (HD) and analyze contributing factors.

Materials and Methods

A cross-sectional study was conducted on dialysis patients at a tertiary care hospital. TE and bioelectrical impedance analysis were performed at four time points: before dialysis, immediately after, the first day after, and the second day after dialysis. LSM values were compared across these time points.

Results

Seventy patients were enrolled, with two cases showing consistently extremely elevated LSM values exceeding 20 kPa, considered outliers. The mean LSM values were 7.6±7.0 kPa before dialysis, 6.12±2.94 kPa immediately after, 6.64±5.27 kPa on the first day, and 6.94±5.12 kPa on the second day after dialysis. The mean pre-HD LSM was significantly higher than immediately after and on the first day after dialysis, with mean differences of 1.54 kPa (95% CI 0.22-2.86, p=0.02) and 1.02 kPa (95% CI 0.15-1.9, p=0.02), respectively. The ultrafiltration volume positively correlated with the LSM difference pre- and post-HD (r=0.315, p=0.008). Patients with residual fluid overload had significantly higher post-HD LSM compared to euvolemic patients (p=0.003).

Conclusion

LSM values significantly decreased after dialysis and remained lower for up to 24 hours. Transient elastography should preferably be performed within 24 hours post-dialysis when the patient is in a euvolemic state.

Development and clinical application of bioelectrical impedance analysis method for body composition assessment

Obesity, which is characterized by excessive body fat, increases the risk of chronic diseases, such as type 2 diabetes, cardiovascular diseases, and certain cancers. Sarcopenia, a decline in muscle mass, is also associated with many chronic disorders and is therefore a major concern in aging populations. Body composition analysis is important in the evaluation of obesity and sarcopenia because it provides information about the distribution of body fat and muscle mass. It is also useful for monitoring nutritional status, disease severity, and the effectiveness of interventions, such as exercise, diet, and drugs, and thus helps assess overall health and longevity. Computed tomography, magnetic resonance imaging, and dual-energy X-ray absorptiometry are commonly used for this purpose. However, they have limitations, such as high cost, long measurement time, and radiation exposure. Instead, bioelectrical impedance analysis (BIA), which was introduced several decades ago and has undergone significant technological advancements, can be used. It is easily accessible, affordable, and importantly, poses no radiation risk, making it suitable for use in hospitals, fitness centers, and even at home. Herein, we review the recent technological developments and clinical applications of BIA to provide an updated understanding of BIA technology and its strengths and limitations.

Muscle Mass and Muscle Strength in Non-Dialysis-Dependent Chronic Kidney Disease Patients

Background: Sarcopenia is a state with a progressive and generalized loss of skeletal muscle mass and strength. However, muscle strength and muscle mass are different features, which are usually not studied separately. The aim of the study was to investigate anthropometric and clinical correlates and sources of variation in both skeletal muscle mass and muscle strength in chronic kidney disease (CKD). Methods: The study sample consisted of 84 patients with an estimated glomerular filtration rate (eGFR) < 45 mL/min/1.73 m2. Muscle strength was estimated by measuring hand grip strength (HGS). Muscle quantity was measured with bioimpedance spectroscopy (BIS). Serum creatinine, urea, uric acid (UA), and albumin were measured as well. Results: Appendicular skeletal muscle mass (ASM) significantly and positively correlated with body mass, NH weight (normally hydrated weight), height, body mass index (BMI), lean tissue mass (LTM), lean tissue index (LTI), fat mass (FM), and fat tissue index (FTI), and was negatively associated with hydration status. HGS significantly and positively correlated with body mass, NH weight, height, LTM, LTI, and ASM, and was negatively associated with UA and urea. After adjustment for age, sex, and height, HGS remained significantly and negatively related with UA and hydration status. Conclusions: In CKD patients, ASM is determined by anthropometric parameters, but HGS is determined by both anthropometric and clinical variables specific for CKD. In order to study the determinants of HGS in CKD, relationships with HGS should be adjusted for anthropometric variables.

C-Reactive Protein-to-Serum Chloride Ratio: A Novel Marker of All-Cause Mortality in Maintenance Haemodialysis Patients

Background and Objectives: hypochloremia is an emerging risk factor for mortality in patients with chronic kidney disease. The pathophysiological mechanisms of this finding are not very clear. Some studies suggest the influence of inflammation as a synergistic factor, so we set out to analyse the association of a novel C-reactive protein-to-serum chloride ratio (CRP/Cl-) with the prognosis of maintenance haemodialysis patients and to assess its relationship with fluid status and body composition measured by bioimpedance. Materials and Methods: the present work is a retrospective cohort study of maintenance haemodialysis patients from our chronic outpatient haemodialysis programme between 1 January 2022 and 31 December 2022. (n = 281). Survival time was collected for all patients and analysed using the Kaplan-Meier method. A Cox proportional hazards regression model was used to evaluate survival probabilities. Variables included in the model were selected using a stepwise selection procedure based on the corrected Akaike information criterion (AICc), which balances model fit and complexity. Results: during a median follow-up of 306 days, 34 patients died. Patients in the fourth quartile of the CRP/Cl- (>0.118 mg/mEq) had higher overall mortality (log-rank test, p = 0.0011). In the Cox multivariate analysis, the variables significantly associated with higher mortality were higher modified Charlson index (MCI), lower body surface area (BSA), lower interdialytic weight gain (IDWG), and higher CRP/Cl- ratio. The latter variable was independently associated with higher overall mortality (adjusted hazard ratio = 1.027; 95% confidence interval [CI], 1.000-1.055 p = 0.0469). Conclusions: Higher CRP/Cl- ratio values were associated with higher all-cause mortality in our maintenance haemodialysis patients.

Can Functional Motor Capacity Influence Mortality in Advanced Chronic Kidney Disease Patients?

Alterations in the body's nutritional status or composition may be observed as the kidney disease advances, which could influence the kidney's functional capacity and, consequently, could increase the risk of mortality. The aim of the study is to determine the influence of functional capacity on mortality assessed by different functional tests in patients with advanced chronic kidney disease (ACKD). A prospective observational study was designed, which included 225 patients followed for 8 years in a CKD clinic. The study assessed functional capacity by using a range of tests, which included the Short Physical Performance Battery, the 6 minutes walking gait test, the timed up and go, and the four versions of the sit-to-stand test. Additionally, body composition and nutritional conditions were considered, taking into consideration various biochemical indicators such as albumin, prealbumin, c-reactive protein (CRP), lymphocytes, and transferrin, muscle strength, comorbidity, and frailty. The relationship between functionality and all-cause mortality was investigated using a Cox proportional hazard model. A total of fifty patients died during the duration of the study. Patients who performed worse on the function and muscle strength tests showed a worse body composition and nutritional status, and exhibited a reduced life expectancy. Inflammation (CRP) was associated with an increased risk of mortality (model 1: hazard ratio (HR) = 1.246; 95% confidence interval (95% CI = 1.014-1.531; model 2: HR = 1.333; 95% CI = 1.104-1.610). Good functional capacity as determined by the SPPB test decreased the risk of mortality (model 1: HR = 0.764; 95% CI = 0.683-0.855; model 2 HR = 0.778; 95% CI = 0.695-0.872). Cut-off points of maximum sensitivity and specificity for mortality were obtained with different tests. The study demonstrated that functional capacity influences mortality in patients with ACKD, being higher in those patients with impaired functionality regardless of the test used, although the SPPB allows a larger number of patients to be assessed. Therefore, it is essential to incorporate the assessment of functionality into the comprehensive care of patients with CKD.

Association of Handgrip Strength and Nutritional Status in Non-Dialysis-Dependent Chronic Kidney Disease Patients: Results from the KNOW-CKD Study

Handgrip strength (HGS) is suggested as an indirect assessment of nutritional status in chronic kidney disease (CKD) patients, but evidence is limited for non-dialysis-dependent CKD (NDD-CKD) patients. This cross-sectional study included 404 patients from the Phase II KoreaN Cohort Study for Outcome in Patients With CKD. HGS, measured twice in each hand, was the exposure, and malnutrition status was defined by a malnutrition-inflammation score (MIS) of 6 or higher. A logistic regression analysis adjusted for age, sex, diabetes mellitus (DM), hypertension, CKD stages, smoking, overhydration, education, and income status was used to assess malnutrition risk. The predictability of HGS for malnutrition was evaluated using the area under the curve (AUC). Patients with lower HGS were older, had a higher prevalence of DM, and lower estimated glomerular filtration rate. Higher HGS was significantly associated with lower malnutrition risk after adjustment (per 1 standard deviation increase, adjusted odds ratio, 0.47 [0.30-0.75]). Subgroup analyses showed no significant interaction between HGS and malnutrition risk across age, sex, DM, and CKD stage. HGS showed fair predictability for malnutrition in men (AUC 0.64 [0.46-0.83]) and women (AUC 0.71 [0.55-0.86]). In conclusion, HGS is a useful diagnostic indicator of malnutrition in NDD-CKD patients.

Making the invisible visible: imaging techniques for assessing muscle mass and muscle quality in chronic kidney disease

Muscle wasting and low muscle mass are prominent features of protein energy wasting (PEW), sarcopenia and sarcopenic obesity in patients with chronic kidney disease (CKD). In addition, muscle wasting is associated with low muscle strength, impaired muscle function and adverse clinical outcomes such as low quality of life, hospitalizations and increased mortality. While assessment of muscle mass is well justified, the assessment of skeletal muscle should go beyond quantity. Imaging techniques provide the means for non-invasive, comprehensive, in-depth assessment of the quality of the muscle such as the infiltration of ectopic fat. These techniques include computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound. Dual energy X-ray absorptiometry is also an imaging technique, but one that only provides quantitative and not qualitative data on muscle. The main advantage of imaging techniques compared with other methods such as bioelectrical impedance analysis and anthropometry is that they offer higher precision and accuracy. On the other hand, the higher cost for acquiring and maintaining the imaging equipment, especially CT and MRI, makes these less-used options and available mostly for research purposes. In the field of CKD and end-stage kidney disease (ESKD), imaging techniques are gaining attention for evaluating muscle quantity and more recently muscle fat infiltration. This review describes the potential of these techniques in CKD and ESKD settings for muscle assessment beyond that of muscle quantity.