Acute renal failure (ARF) is a multidisciplinary and common clinical critical illness caused by multiple etiologies. Although research on the pathophysiology and pathogenesis of ARF has made great progress in recent decades, the mortality rate of ARF is still high, up to 50%±. The situation of ARF prevention and treatment is still very serious. At present, the following problems exist in the diagnosis and treatment of ARF: the incidence of ARF is on the rise due to the lack of effective preventive measures, coupled with the aging of the population and the extensive development of various major surgeries; the lack of effective predictive and early diagnostic indicators for ARF, thus missing the best time for intervention; the lack of standardized treatment for critical ARF, especially the choice of blood purification methods, dialysis dose, etc. There is no unified opinion on key issues; critical ARF mainly occurs in surgery, intensive care units, etc., and close multidisciplinary collaboration is especially important for diagnosis and treatment, but no effective multidisciplinary joint model has been formed yet. Definition and diagnosis of acute kidney injury There is no consensus on the definition of ARF for a long time, which makes it difficult to compare the results of different studies and affects the improvement of ARF diagnosis and treatment to a certain extent. Most scholars believe that the early diagnosis, intervention and attention to ARF are currently insufficient. In recent years, a large number of clinical studies have shown that a mild impairment of renal function can lead to an increase in morbidity and mortality [1]. Therefore, the international nephrology and emergency medicine community now tends to rename acute renal failure as acute kidney injury (AKI). The expectation is to identify ARF as early as possible, at the stage when GFR starts to decline or even when there is damage to the kidney (histological and biomarker changes) while GFR is still normal, in order to intervene early. In 2002, the acute dialysis quality initiative group (ADQI) developed the “RIFLE” stratified diagnostic criteria for AKI [2], which classify AKI into 5 levels: risk of renal dysfunction (R), injury to the kidney (I), failure of kidney function (F), loss of kidney function (L), and end-stage kidney disease (ESKD). disease (ESKD). However, this new classification criteria still has some limitations, such as the sensitivity and specificity of the diagnosis of AKI is not high, and the influence of age, gender and race on creatinine is not considered. In 2005, the Acute Kidney Injury Network (AKIN) developed a new consensus on acute kidney injury in Amsterdam, the Netherlands.3 AKIN defines AKI as functional or structural abnormalities of the kidney not older than 3 months, including abnormalities in blood, urine, tissue testing, or imaging markers of kidney injury. The diagnostic criteria for AKI are: a sudden decrease in renal function (within 48 h). This is manifested by an absolute increase in blood creatinine of ≥0.3 mg/dL (≥26.4 mmol/L); or an increase in blood creatinine of ≥50% from basal values; or a decrease in urine output (urine output <0.5 ml? The AKIN consensus still used the RIFLE classification, but only the first 3 acute phases were retained, and the classification criteria were adjusted. See Table 1 for details. the AKIN consensus specifies a time window (48h) for the diagnosis of AKI, emphasizing the dynamic changes in blood creatinine and providing the possibility of early clinical intervention in AKI. In addition, compared with the ADQI consensus, the AKIN consensus specifies that AKI can be diagnosed with a slight increase in blood creatinine ≥0.3 mg/dL, improving the sensitivity of the diagnosis. It should be noted that some factors affecting urine output such as urinary tract obstruction, blood volume status, and diuretic use must be taken into account when using urine output changes alone as diagnostic and staging criteria. Since AKI is a clinical syndrome, the applicability of the AKIN consensus to AKI of different etiologies and in different clinical situations needs to be confirmed by a large number of clinical studies. In addition, because of the numerous factors affecting blood creatinine and its poor sensitivity. Therefore, blood creatinine is not the best marker of kidney injury. The search for other more specific and sensitive markers of AKI is still a direction for future AKI research. Some valuable markers have been identified, such as kidney injury molecule-1 (KIM-1) [4], neutrophil gelatinase-associated lipid transport protein (NGAL) [5], sodium-hydrogen exchanger 3 (NHE3) [6], interleukin-18 (IL-18) [7], cysteine-rich, heparin-binding protein (Cyr61) [8], but more in-depth studies are needed. Treatment of acute kidney injury The treatment of AKI includes symptomatic supportive therapy and renal replacement therapy. Adequate fluid supplementation has been well established for the prevention and treatment of pre-renal and contrast kidney injury. The early use of certain drugs may have some preventive effect on ATN, such as the selective dopamine receptor 1 agonist fenoldopam [9], free radical scavengers and antioxidants, and hexoketococine [10], but they have not been confirmed by prospective randomized controlled studies. Hemoperfusion therapy is an important component of AKI treatment, including peritoneal dialysis (PD), intermittent renal replacement therapy (IRRT), and continuous renal replacement therapy (CRRT). Although PD is currently less commonly used for the treatment of severe AKI compared to CRRT. However, because PD is less expensive and does not require anticoagulants, it is still a common treatment for AKI in less economically developed countries and regions and when a large number of patients need treatment for catastrophic events [11]. In recent years, a number of important advances have been made in the hemodialysis treatment of critically ill AKI, especially regarding the dosage and timing of CRRT, and some new alternative treatment modalities such as continuous low-efficiency daily dialysis (SLEDD) have emerged. Regarding IRRT versus CRRT, intermittent hematology (IHD) and continuous hydrostatic hemofiltration/continuous hydrostatic hemodialysis filtration are still the most commonly used in clinical practice, but there is not enough information to suggest which treatment modality is better [12-15]. CRRT is extremely common in the ICU because of its characteristics such as more stable hemodynamics and the ability to remove some inflammatory mediators, and the most important precipitating factor of ARF in the ICU is infectious shock. However, the results of some existing prospective randomized controlled studies suggest that there may be no significant difference between IHD and CRRT in terms of patient mortality and recovery of renal function. Some studies have also found that CRRT facilitates the recovery of renal function, although it is not significantly better than IRRT in terms of overall patient mortality. Another author [16] concluded that the adequacy of the replacement therapy dose seems to be more important than the choice of replacement modality in terms of its impact on patient mortality and recovery of renal function. SLEDD and extended daily dialysis (EDD) can be considered as a compromise between IHD and CRRT. It has similar rapid solute clearance to IHD and similar cardiovascular tolerability to CRRT, with lower doses of anticoagulants such as heparin than CRRT, does not require expensive CRRT machines, specially formulated sterile replacement solutions and dedicated medical staff, and facilitates other necessary treatments and investigations during off-treatment hours. alternative treatment of critical AKI in the ICU can be an alternative modality to conventional CRRT [17]. However, there is a lack of information from prospective randomized controlled studies on SLEDD or EDD compared with CRRT. Regarding the timing of CRRT. Currently recognized indications for emergency dialysis include volume overload, hyperkalemia, metabolic acidosis, and overt signs and symptoms of uremia. However, there is no consensus on when to initiate renal replacement therapy in patients with AKI, with a preference for early initiation of renal replacement therapy in severe AKI. In recent years, an increasing number of studies have suggested that early initiation of CRRT therapy can improve the prognosis of critically ill patients [18-20]. However, there is no previous consensus on the criteria for quantifying early renal replacement therapy. The ongoing IVOIRE study is an intervention with grade I of the RIFLE grading system proposed by ADQI as an early criterion. Regarding the dose and intensity of CRRT. Many studies have shown that patients with high CRRT dose/intensity have a better prognosis [21-22].Ronco et al. suggest that the "dose for sepsis" of hemofiltration in the treatment of ARF in sepsis should probably be higher than the dose for ARF in critically ill patients without a systemic inflammatory response "Dose to replace the kidney". At the 2001 Melbourne meeting of the International Society of Critical Care Nephrology, it was recommended that hemofiltration in patients with sepsis be classified according to the volume of replacement fluid. Replacement doses below 35 ml/kg/h are considered inadequate, very low-volume hemofiltration (VLVHF), while doses between 35 ml/kg/h and 50 ml/kg/h are considered low-volume hemofiltration (LVHF), (LVHF), which is the "renal replacement dose", and doses above 50 ml/kg/h are considered as high-volume hemofiltration (HVHF), which can also be called "sepsis treatment dose ". However, in clinical practice, the high-dose RRT treatment strategy has not been widely used. The exact dose of CRRT for sepsis-associated severe ARF is still uncertain, is the higher the dose the better the outcome? What is the highest dose? Some studies suggest that high doses of CRRT can reduce mortality in patients. It is generally accepted that the replacement dose or ultrafiltration rate should be weight-based, at least 35 mL/kg/h. Whether higher ultrafiltration rates (>50 mL/kg/h) can further reduce mortality is unclear. Recently, the ongoing ATN study in the United States and the RENAL study in Australia and New Zealand and the IVOIRE study in France, to be completed by the end of 2008, were designed precisely to better evaluate the relationship between the dose/intensity of renal replacement therapy in severe ARF and patient prognosis. One of these studies, the IVOIRE study, is a randomized, prospective clinical study comparing two hemofiltration treatment regimens in patients with septic shock with ARF in the ICU. One group of patients will be treated with early high volume hemofiltration (70 ml/kg/min) and the other group will receive standard volume hemofiltration (35 ml/kg/min), respectively, with promising results. However, until the results of new multicenter clinical studies are available, at least for the time being, ARF patients should receive hemodialysis at a dose of ≥35 ml/kg/h, whether with HF, HDF or daily dialysis. In addition, the main cause of death in critically ill ARF patients is extrarenal complications, and how to improve the treatment of extrarenal complications is one of the urgent challenges. At present, there are constantly studies suggesting that some blood purification therapies such as high volume hemofiltration may have some new therapeutic effects in the treatment of sepsis/MODS, such as removing some inflammatory mediators and regulating the inflammatory response of the body; improving the function of immune cells and reestablishing the immune endostasis of the body; and supporting the extra-renal organ systems such as the heart, lung and peripheral circulation, which deserve further in-depth study. In conclusion, the prevention and treatment of ARF is still a serious issue, and the development of diagnostic criteria and staging of AKI will facilitate interdisciplinary cooperation and communication in AKI research and solve the practical clinical problems in the treatment of AKI. The treatment of AKI today is mainly supportive, including proper fluid control, nutritional support and renal replacement therapy, emphasizing early prevention, early treatment and individualized treatment for different etiologies and conditions. The development of renal replacement therapy in the treatment of critical AKI is very promising and deserves our common attention.