Background A comprehensive evaluation of the independent and combined associations of estimated glomerular filtration rate (eGFR) and albuminuria with mortality is required for assessment of the impact of kidney function on risk in the general population, with implications for improving the definition and staging of chronic kidney disease (CKD). Methods A collaborative meta-analysis of general population cohorts was undertaken to pool standardized data for all-cause and cardiovascular mortality. The two kidney measures and potential confounders from 14 studies (105,872 participants; 730,577 person-years) with urine albumin-to-creatinine ratio (ACR) measurements and seven studies (1,128,310 participants; 4,732,110 person-years) with urine protein dipstick measurements were modeled. Findings In ACR studies, mortality risk was unrelated to eGFR between 75-105 ml/min/1·73 m2 and increased at lower eGFR. Adjusted hazard ratios (HRs) for all-cause mortality at eGFR 60, 45, and 15 (versus 95) ml/min/1·73 m2 were 1·18 (95% CI: 1·05-1·32), 1·57 (1·39-1·78), and 3·14 (2·39-4·13), respectively. ACR was associated with mortality risk linearly on the log-log scale without threshold effects. Adjusted HRs for all-cause mortality at ACR 10, 30, and 300 (versus 5) mg/g were 1·20 (1·15-1·26), 1·63 (1·50-1·77), and 2·22 (1·97-2·51). eGFR and ACR were multiplicatively associated with mortality without evidence of interaction. Similar findings were observed for cardiovascular mortality and in dipstick studies. Interpretation Lower eGFR (<60 ml/min/1·73 m2) and higher albuminuria (ACR ≥10 mg/g) were independent predictors of mortality risk in the general population. This study provides quantitative data for using both kidney measures for risk evaluation and CKD definition and staging.

Importance The established chronic kidney disease (CKD) progression endpoint, end-stage renal disease (ESRD) or doubling of serum creatinine (corresponding to a change in estimated glomerular filtration rate (eGFR) of −57% or greater) is a late event, limiting feasibility of nephrology clinical trials. Objective To characterize the association of decline in eGFR with subsequent progression to ESRD, with implications for using lesser declines in eGFR as potential alternative endpoints for CKD progression. Since most people with CKD die before reaching ESRD, we also investigated mortality risk. Data Sources Individual meta-analysis of up to 1.7 million participants with 12,344 ESRD events and 223,944 deaths from 35 cohorts. Study Selection Cohorts in the CKD Prognosis Consortium with a repeated measure of serum creatinine over 1-3 years and outcome data. Data Extraction and Synthesis Transfer of individual participant data or standardized analysis of outputs for random effects meta-analysis took place between July 2012 and September 2013 with baseline eGFRs during 1975-2012. Main Outcomes and Measures ESRD (initiation of dialysis or transplantation) or all-cause mortality risk related to percent change in eGFR over 2 years adjusted for potential confounders and first eGFR. Results The adjusted hazard ratios (HR) of ESRD and mortality were exponentially higher with larger eGFR decline. Among participants with baseline eGFR <60 ml/min/1.73m2, the adjusted HRs for ESRD were 32.1 (95% CI 22.3-46.3) and 5.4 (4.5-6.4) for −57% and −30% eGFR changes, respectively. However, changes of −30% or greater were much more common than changes of −57% (6.9% (6.4-7.4%) vs. 0.79% (0.52-1.06%) in the whole consortium). This association was strong and consistent across length of baseline (1 or 3 years), baseline eGFR, age, diabetes status, or albuminuria. Average adjusted 10-year risk of ESRD for eGFR changes of −57%, −40%, −30% and 0% were 99% (95-100%), 83% (71-93%), 64% (52-77%), vs. 18% (15-22%) respectively at baseline eGFR of 35 ml/min/1.73m2. Corresponding mortality risks were 77% (71-82%), 60% (56-63%), 50% (47-52%), vs. 32% (31-33%), showing a similar but weaker pattern. Conclusions and Relevance Declines in eGFR smaller than doubling of serum creatinine occur more commonly and are strongly and consistently associated with the risk of ESRD and mortality, supporting consideration of lesser declines in eGFR, such as 30% reduction over 2 years, as an alternative endpoint for CKD progression.

Ischemia/reperfusion injury (IRI) may activate innate immunity through the engagement of TLRs by endogenous ligands. TLR4 expressed within the kidney is a potential mediator of innate activation and inflammation. Using a mouse model of kidney IRI, we demonstrated a significant increase in TLR4 expression by tubular epithelial cells (TECs) and infiltrating leukocytes within the kidney following ischemia. TLR4 signaling through the MyD88-dependent pathway was required for the full development of kidney IRI, as both TLR4 -/-and MyD88 -/-mice were protected against kidney dysfunction, tubular damage, neutrophil and macrophage accumulation, and expression of proinflammatory cytokines and chemokines. In vitro, WT kidney TECs produced proinflammatory cytokines and chemokines and underwent apoptosis after ischemia. These effects were attenuated in TLR4 -/-and MyD88 -/-TECs. In addition, we demonstrated upregulation of the endogenous ligands high-mobility group box 1 (HMGB1), hyaluronan, and biglycan, providing circumstantial evidence that one or more of these ligands may be the source of TLR4 activation. To determine the relative contribution of TLR4 expression by parenchymal cells or leukocytes to kidney damage during IRI, we generated chimeric mice. TLR4 -/-mice engrafted with WT hematopoietic cells had significantly lower serum creatinine and less tubular damage than WT mice reconstituted with TLR4 -/-BM, suggesting that TLR4 signaling in intrinsic kidney cells plays the dominant role in mediating kidney damage.

Recurrence is an important cause of allograft loss for those with renal failure due to glomerulonephritis. No risk factors for recurrence were identified that warrant altering the approach to transplantation. However, accurate estimates of risk can now be provided to potential recipients of renal allografts.