Darren Green

Estimates of glomerular filtration rate (eGFR) should provide accurate measure of an individual's kidney function because important clinical decisions such as timing of renal replacement therapy and drug dosing may be dependent on eGFR. Formulae from which eGFR is derived are generally based on serum creatinine measurement, such as Cockcroft-Gault, MDRD and CKD-EPI. More recently, calculation of eGFR using other laboratory biomarkers such as cystatin C has emerged with apparent greater accuracy. In old people, there is age-related physiological change in the kidney, which could lead to reduced GFR. Likewise, physiological changes in body composition that occur with the ageing process impede the use of a single creatinine-based calculation of eGFR across all adult age groups. Studies have shown differences in the prevalence of CKD based on the type of equation used to estimate GFR. This review discusses the evolution of eGFR calculations and the relative accuracy of such equations in older population.

BACKGROUND: Around 16% of all patients who present with atheromatous renovascular disease (ARVD) in the United States undergo revascularization. Historically, patients with advanced chronic kidney disease (CKD) have been considered least likely to show improvement in renal functional terms, or survival. We aimed to investigate whether differences in outcomes after revascularization compared to medical management might be observed in ARVD patients if stratified by their CKD classes. METHODS: Two prospective cohorts, a UK center with a traditionally conservative approach, and a German center who undertook a proactive revascularization approach, were compared. An improvement in renal function was defined as > 20% renal improvement at one year's follow-up. To improve validity and comparability, revascularized patients in the UK center were also used within analyses, RESULTS: 347 (UK conservative group), 89 (UK revascularized group), and 472 (German center) patients were included in the analysis. When subdivided by CKD stage, patient ages between the two centers were comparable. Improvements in renal function were observed in twice as many patients who underwent revascularization as compared to medical treatment, particularly in the latter CKD stages, 15.2 (German revascularization) vs. 0% in CKD 1-2, 12.2 (UK), and 32.8 (German) revascularization vs. 14.1% in CKD3, and 53.1 and 53.8 vs. 28.3 in patients with CKD 4-5. The improvements in eGFR were 10.2 (16) and 8.1 (12.5) ml/min/year in the German and UK revascularized groups, respectively, vs. -0.05 (6.8) ml/min/year in the medical cohort in CKD 4-5. Improvements in blood pressure control were noted at 1 year overall and within each CKD category. Multivariate analysis revealed that revascularization independently reduced the risk of death by 45% in all patients combined (RR 0.55, P = 0.013). CONCLUSIONS: Although this study has significant methodological limitations, it does shows that percutaneous renal revascularization can improve renal function in advanced CKD (stages 4-5), and that this can provide a survival advantage in prospective analysis.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is an independent risk factor associated with cardiovascular disease (CVD) and incidence of chronic kidney disease (CKD). NAFLD is threatening to become a major public health problem in association with the metabolic syndrome. The association of NAFLD with outcomes in patients with advanced CKD has not been evaluated. In this study, the prevalence of NAFLD and its impact on cardiovascular and renal outcomes and mortality were determined in a large secondary care CKD cohort. METHODS: The study was conducted on 1148 CKD patients within a cohort of 3061 CKD patients, who had undergone ultrasound imaging of the liver over a 15-year period. A propensity-matched population from within the cohort was also included. Cox regression analysis was used to study the association of NAFLD with cardiovascular events, end-stage renal disease and mortality and linear regression analysis for CKD progression. RESULTS: The prevalence of NAFLD was 17.9%. The median duration of follow-up after scanning was 5.4 years, with a median estimated glomerular filtration rate (eGFR) of 33.5 mL/min/1.73 m2 in this population. NAFLD proved to be a strong independent risk factor for cardiovascular events [hazard ratio (HR) 2.03; 95% confidence interval (CI) 1.33-3.13; P < 0.01] but it was not associated with all-cause mortality (HR 0.79; 95% CI 0.58-1.08; P = 0.14) or CKD progression (P = 0.09 for rate of decline of eGFR slope). Patients with CKD are known to have high cardiovascular risk; the propensity-matched analysis showed that NAFLD increased this cardiovascular risk (HR 2.00; CI 1.10-3.66; P < 0.05). CONCLUSIONS: NAFLD has a strong independent association with cardiovascular events, even in an advanced CKD cohort with high comorbidity. The implication is that routine screening for NAFLD may be warranted in CKD populations to enable targeted interventions for CVD prevention in higher risk patients.