In the general population, a high body mass index (BMI; in kg/m(2)) is associated with increased cardiovascular disease and all-cause mortality. However, the effect of overweight (BMI: 25-30) or obesity (BMI: >30) in patients with chronic kidney disease (CKD) undergoing maintenance hemodialysis (MHD) is paradoxically in the opposite direction; ie, a high BMI is associated with improved survival. Although this "reverse epidemiology" of obesity or dialysis-risk-paradox is relatively consistent in MHD patients, studies in CKD patients undergoing peritoneal dialysis have yielded mixed results. Growing confusion has developed among physicians, some of whom are no longer confident about whether to treat obesity in CKD patients. A similar reverse epidemiology of obesity has been described in geriatric populations and in patients with chronic heart failure (CHF). Possible causes of the reverse epidemiology of obesity include a more stable hemodynamic status, alterations in circulating cytokines, unique neurohormonal constellations, endotoxin-lipoprotein interaction, reverse causation, survival bias, time discrepancies among competitive risk factors, and malnutrition-inflammation complex syndrome. Reverse epidemiology may have significant clinical implications in the management of dialysis, CHF, and geriatric patients, ie, populations with extraordinarily high mortality. Exploring the causes and consequences of the reverse epidemiology of obesity in dialysis patients can enhance our insights into similar paradoxes observed for other conventional risk factors, such as blood pressure and serum cholesterol and homocysteine concentrations, and in other populations such as those with CHF, advanced age, cancer, or AIDS. Weight-gaining interventional studies in dialysis patients are urgently needed to ascertain whether they can improve survival and quality of life.

Diminished appetite (anorexia) is associated with higher concentrations of proinflammatory cytokines and higher levels of erythropoietin hyporesponsiveness and poor clinical outcome, including a 4-fold increase in mortality, greater hospitalization rates, and a poor QoL in MHD patients. Appetite status may yield significant insight into the clinical status of dialysis patients.

A low baseline body fat percentage and fat loss over time are independently associated with higher mortality in MHD patients even after adjustment for demographics and surrogates of muscle mass and inflammation, whereas a tendency toward a worse QoL is reported by MHD patients with a higher body fat percentage. Obesity management in dialysis patients may need reconsideration.

Although the emergence of erythropoiesis-stimulating agents has revolutionized the anemia management of chronic kidney disease (CKD) in the past two decades, strategies to assess iron (Fe) status and to provide Fe supplementation have remained indistinct. The reported cases of hemochromatosis in dialysis patients from the pre-erythropoiesis-stimulating agent era along with the possible associations of Fe with infection and oxidative stress have fueled the "iron apprehension." To date, no reliable marker of Fe stores in CKD has been agreed on. Serum ferritin continues to be the focus of attention. Almost half of all maintenance hemodialysis patients have a serum ferritin >500 ng/ml. In this ferritin range, Fe supplementation currently is not encouraged, although most reported hemochromatosis cases had a serum ferritin >2000 ng/ml. The moderate-range hyperferritinemia (500 to 2000 ng/ml) seems to be due mostly to non-Fe-related conditions, including inflammation, malnutrition, liver disease, infection, and malignancy. Recent epidemiologic studies have shown that a low, rather than a high, serum Fe is associated with a poor survival in maintenance hemodialysis patients. In multivariate adjusted models that mitigate the confounding effect of malnutrition-inflammation, serum ferritin <1200 ng/ml and Fe saturation ratio in 30 to 50% range are associated with the greatest survival in maintenance hemodialysis patients. Although ferritin is a fascinating molecule, moderate hyperferritinemia is a misleading marker of Fe stores in patients with CKD. It may be time to revisit the utility of serum ferritin in CKD and ask ourselves whether its measurement has helped us or has caused more confusion and controversy.

The impact of dietary patterns and the commensal microbiome on susceptibility to and severity of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has been largely ignored to date. In this Perspective, we present a rationale for an urgent need to investigate this possible impact and therapeutic options for COVID-19 based on dietary and microbiome modifications. The mitigating role of nanotechnology with relation to the impact of SARS-CoV-2 virus is highlighted.

In patients with ESRD, residual kidney function (RKF) contributes to achievement of adequate solute clearance. However, few studies have examined RKF in patients on hemodialysis. In a longitudinal cohort of 6538 patients who started maintenance hemodialysis over a 4-year period (January 2007 through December 2010) and had available renal urea clearance (CL) data at baseline and 1 year after hemodialysis initiation, we examined the association of annual change in renal CL rate with subsequent survival. The median (interquartile range) baseline value and mean±SD annual change of CL were 3.3 (1.9-5.0) and -1.1±2.8 ml/min per 1.73 m, respectively. Greater CL rate 1 year after hemodialysis initiation associated with better survival. Furthermore, we found a gradient association between loss of RKF and all-cause mortality: changes in CL rate of -6.0 and +3.0 ml/min per 1.73 m per year associated with case mix-adjusted hazard ratios (95% confidence intervals) of 2.00 (1.55 to 2.59) and 0. 61 (0.50 to 0.74), respectively (reference: -1.5 ml/min per 1.73 m per year). These associations remained robust against adjustment for laboratory variables and ultrafiltration rate and were consistent across strata of baseline CL, age, sex, race, diabetes status, presence of congestive heart failure, and hemoglobin, serum albumin, and serum phosphorus levels. Sensitivity analyses using urine volume as another index of RKF yielded consistent associations. In conclusion, RKF decline during the first year of dialysis has a graded association with all-cause mortality among incident hemodialysis patients. The clinical benefits of RKF preservation strategies on mortality should be determined.

Background Acute kidney injury (AKI) is a serious global public health problem. We aimed to quantify the risk of AKI associated with estimated glomerular filtration rate (eGFR), albuminuria (albumin-creatinine ratio [ACR]), age, sex, and race (African American and Caucasian). Study Design Collaborative meta-analysis. Setting & Population 8 general population cohorts (1,285,049 participants) and 5 chronic kidney disease (CKD) cohorts (79,519 participants). Selection Criteria for Studies Available eGFR, ACR, and ≥50 AKI events. Predictors Age, sex, race, eGFR, urine ACR, and interactions. Outcome Hospitalized with or for AKI, using Cox proportional hazards models to estimate HRs of AKI and random effects meta-analysis to pool results. Results 16,480 (1.3%) general population cohort participants had AKI over a mean follow-up of 4 years; 2,087 (2.6%) CKD participants had AKI over mean follow-up of 1 year. Lower eGFR and higher ACR were strongly associated with AKI. Compared with eGFR 80 ml/min/1.73 m2, the adjusted HR of AKI at eGFR 45 ml/min/1.73 m2 was 3.35 (95% CI, 2.75–4.07). Compared with ACR 5 mg/g, the risk of AKI at ACR 300 mg/g was 2.73 (95% CI, 2.18–3.43). Older age was associated with higher risk of AKI, but this effect was attenuated in lower eGFR or higher ACR. Male sex was associated with higher risk of AKI, with a slight attenuation in lower eGFR but not in higher ACR. African Americans had higher AKI risk at higher levels of eGFR and most levels of ACR. Limitations Only 2 general population cohorts could contribute to analyses by race; AKI identified by diagnostic code. Conclusions Reduced eGFR and increased ACR are consistent, strong risk factors for AKI whereas the associations of AKI with age, sex, and race may be weaker in more advanced stages of CKD.

Nutritional assessment of patients with chronic kidney disease is a vital function of health care providers. Subjective Global Assessment (SGA) is a tool that uses 5 components of a medical history (weight change, dietary intake, gastrointestinal symptoms, functional capacity, disease and its relation to nutritional requirements) and 3 components of a brief physical examination (signs of fat and muscle wasting, nutrition-associated alternations in fluid balance) to assess nutritional status. SGA was originally used to predict outcomes in surgical patients; however, its use has gone beyond this function and population. In chronic kidney disease patients, SGA is incorporated into the complete nutritional assessment. Validation of SGA as a screening tool for surgical patients was done by Detsky et al in 1984. Since that time, SGA has been altered by different researchers and clinicians to better meet the needs of the patients they served. Validation of the altered SGA formats has not been thoroughly done. Further work in establishing validity and reliability of each version of SGA in different patient populations should be done to enable clinicians and researchers to properly use this nutritional assessment tool.