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The Acute Kidney Injury Network (AKIN) met in Amsterdam, The Netherlands, in September 2005. At the 2-day meeting, participants in this multidisciplinary collaboration proposed a standard definition, and scheme for the classification, of AKI. Widespread adoption of these standards, presented here by members of the AKIN working group, would help to advance the study of this condition, and improve patient outcomes.

The first of this pair of 'pro/con' Viewpoints sets out the case for the superiority of continuous renal replacement therapy over intermittent hemodialysis in critically ill patients with acute kidney injury. Forming the basis of the author's argument is the notion that by attempting to correct in a few minutes physiological derangements that have developed over hours or days, intermittent hemodialysis is aggressive and unphysiological; by contrast, continuous renal replacement therapy corrects derangements gently and slowly, like the native kidneys.

The development of a wearable device that can replace conventional dialysis in patients needing chronic renal replacement therapy is not as far-fetched as it once was. Ronco et al. describe technological achievements, propose future research directions and discuss the clinical, technical and socioeconomic reasons for continuing the push to realize the wearable artificial kidney.

The kidney and the brain exhibit extensive organ crosstalk due to similarities in their vasculature and shared humoral and non-humoral pathways. In this Review, Claudio Ronco et al. evaluate the effects of chronic kidney disease, end-stage renal disease, and acute kidney injury on cognitive and cerebrovascular function. The authors also highlight the risk factors for cognitive impairment in patients undergoing dialysis.

The authors of this Viewpoint argue that the currently used definitions of cardiorenal syndrome fail to take into account the complex bidirectional nature of the relationship between the heart and kidneys. They propose a new classification of the condition, comprising five subtypes that are distinguished on the basis of the primary and secondary pathology and its chronology. Examples of each subtype are provided.

A recent report showed that hypophosphatemia is common in children undergoing continuous renal replacement therapy, and that adding phosphate to the replacement and dialysate solutions significantly reduced the incidence of this complication. Should such supplementation be routinely performed?

Emerging evidence suggests that 15–20% of patients who do not fulfill current consensus criteria for AKI have acute tubular damage, which is associated with adverse outcomes. Haase et al. argue that the spectrum of AKI should be extended to incorporate subclinical forms of the disorder diagnosed on the basis of biomarkers of tubular damage.

The abstract of the RENAL Replacement Therapy study concludes that in critically ill patients with acute kidney injury, treatment with higher-intensity continuous renal replacement therapy did not reduce mortality. However, the real news is that survival and recovery of renal function might depend on how therapy is provided.

Hsu et al. report a progressive increase in the incidence of dialysis-requiring acute kidney injury (AKI) and associated deaths in the USA between 2000 and 2009. As with chronic kidney disease, a concerted campaign to increase awareness and alertness of AKI is urgently required. We must prevent “kidney attack”.

Information technology is being increasingly used in medicine to improve patient care and safety. Computerized physician order entry and clinical decision support systems have been shown to reduce the rate of adverse drug events, which are a frequent cause of morbidity and mortality and are of increased likelihood in patients with renal impairment. The authors of this Review discuss the benefits and limitations of computerized support systems and outline features that can be refined to encourage the implementation of these tools.

Sepsis is the most common and severe cause of morbidity and mortality among critically ill patients. Acute kidney injury (AKI) can complicate sepsis, with a linear relationship between the severity of kidney damage and patient prognosis. In this Review, the authors describe currently available interventions for sepsis-related AKI. In addition, they discuss preventive methods, pharmacological support and extracorporeal blood purification for septic AKI.

Here, the authors provide guidance on the prevention, diagnosis and management of anticancer therapy nephrotoxicity in adult patients. They also define a research agenda focused on preventing and mitigating anticancer therapy toxicity, maximizing early detection of nephrotoxicity and enabling optimal drug dosing in patients with kidney disease.

The concepts of kidney damage and dysfunction, including subclinical damage and loss of renal functional reserve, are relevant to the detection of acute kidney injury (AKI). Here, the authors examine these concepts, as well as AKI duration and relapse, and discuss potential changes to AKI classification criteria.

Haemodialysis membranes are traditionally classified on the basis of their composition and water permeability. In this Review, the authors discuss the advances in materials technology, polymer chemistry, surface functionalization and dialyser assembly that mandate new classification approaches.

Elderly hospitalized patients are at high risk of developing acute kidney injury (AKI). In this Review, Alexandra Chronopoulos and colleagues discuss the reasons for the increased risk of AKI in this patient group, including age-related changes in the kidney, systemic vasculature, and immunological system, as well as frequent comorbidities and high exposure to iatrogenic insults such as medications, radiocontrast agents, and surgery. The difficulties of treating AKI in older individuals are also described, and the importance of early diagnosis is emphasized.

Intravenous fluids are widely administered to patients who have, or are at risk of, acute kidney injury (AKI), but deleterious consequences of overzealous fluid therapy are increasingly being recognized. This Review describes the problems of fluid management in acquired AKI, and discusses the need to balance the competing needs of adequate fluid resuscitation, the avoidance of progressively positive fluid balances (which can lead to extracellular volume expansion and organ edema), and the possibility of overzealous fluid removal (which can lead to hypovolemic AKI).

Acute kidney injury (AKI) is often overlooked in hospitalized patients, despite a strong association with poor clinical outcomes. In this Review, Ricci et al. discuss the advantages and limitations of the RIFLE and AKIN consensus definitions for AKI. The authors also consider the integration of novel biomarkers into these definitions to aid early diagnosis and prediction of the prognosis of AKI.

A recent observational study reports that after cardiac surgery, clinical outcomes differ significantly between patients with the same stage of acute kidney injury (AKI) depending on the diagnosis criteria used: urine output, serum creatinine or both. This finding emphasizes the limitations of current criteria for AKI risk stratification and diagnosis.

Pregnancy-associated acute kidney injury is a risk factor for maternal and fetal morbidity and mortality and a driver of health inequity worldwide. This Consensus Statement from the Acute Disease Quality Initiative provides recommendations on the causes, diagnosis, management and follow-up of pregnancy-associated acute kidney injury.

Antibodies against several podocyte antigens have evolved as markers of diagnosis, disease activity, and prognosis in membranous nephropathy, but their pathogenic role remains debated. Detailed work-up of two cases of primary and secondary membranous nephropathy now supports the concept that thrombospondin type-1 domain-containing 7A autoantibodies are pathogenic.

Decreasing susceptibility to tissue damage — a protective strategy known as tolerance — might be as important as infection resistance in determining outcomes in sepsis. Here, the authors discuss tolerance mechanisms that act in the kidney during sepsis, with a focus on the role of metabolic reprogramming.

The prevalence of direct kidney involvement in novel coronavirus disease (COVID-19) is low, but such involvement is a marker of multiple organ dysfunction and severe disease. Here, we explore potential pathways of kidney damage and discuss the rationale for extracorporeal support with various blood purification strategies in patients who are critically ill with COVID-19.

Acute kidney injury (AKI) and chronic kidney disease are increasingly recognized as interconnected entities and the term acute kidney disease (AKD) has been proposed to define ongoing pathophysiologic processes following an episode of AKI. In this Consensus statement, the Acute Disease Quality Initiative 16 Workgroup propose definitions and staging criteria for AKD, and strategies for the management of affected patients. They also make recommendations for areas of future research with the aims of improving understanding of the underlying processes and improving outcomes.

Ali Gharavi and colleagues report a genome-wide association analysis of IgA nephropathy in over 20,000 individuals of European and East Asian ancestry. They identify genome-wide significant signals at three new loci near VAV3, CARD9 and ITGAM-ITGAX and correlations between genetic risk and pathogen diversity.

COVID-19-associated AKI (COVID-19 AKI) is associated with high mortality and is an independent risk factor for all-cause in-hospital death in patients with COVID-19. This Consensus Statement from the Acute Disease Quality Initiative provides recommendations for the diagnosis, prevention and management of COVID-19 AKI and for areas of future research, with the aim of improving understanding of the underlying processes and outcomes for patients with COVID-19 AKI.

Several factors complicate the identification of effective interventions that can improve the outcomes of patients with acute kidney injury (AKI). Here, the authors discuss key design considerations for clinical trials in hospitalized patients with AKI, including the selection of adequate patient cohorts and study end points.

Acute kidney injury (AKI) describes a sudden loss of excretory kidney function that can result in long-term kidney damage. This Primer describes AKI epidemiology and pathophysiology in different economic settings, discusses current diagnostic and management principles, and highlights long-term effects on quality of life and initiatives to improve patient care.

In this Consensus Statement, the authors discuss a framework for the development, validation and implementation of digital health technologies across the acute kidney injury continuum — risk prediction, prevention, detection and management.

Sepsis-associated acute kidney injury (SA-AKI) is linked with poor outcomes in critically ill patients. This Consensus Statement from the Acute Disease Quality Initiative discusses the definition, epidemiology and pathophysiology of SA-AKI, fluid, resuscitation and extracorporeal therapies, and the role of biomarkers in risk stratification and diagnosis.

The development of acute kidney injury (AKI) after major non-cardiac surgery is associated with substantial long-term morbidity and mortality. This joint Consensus Statement from the Acute Disease Quality Initiative and the PeriOperative Quality Initiative provides recommendations for the definition, prevention and management of postoperative AKI.