Acute kidney injury (AKI), previously called acute renal failure (ARF), is a sudden decrease in kidney function that develops within 7 days, as shown by an increase in serum creatinine or a decrease in urine output, or both.Causes of AKI are classified as either prerenal (due to decreased blood flow to the kidney), intrinsic renal (due to damage to the kidney itself), or postrenal (due to blockage of urine flow). Prerenal causes of AKI include sepsis, dehydration, excessive blood loss, cardiogenic shock, heart failure, cirrhosis, and certain medications like ACE inhibitors or NSAIDs. Intrinsic renal causes of AKI include glomerulonephritis, lupus nephritis, acute tubular necrosis, certain antibiotics, and chemotherapeutic agents. Postrenal causes of AKI include kidney stones, bladder cancer, neurogenic bladder, enlargement of the prostate, narrowing of the urethra, and certain medications like anticholinergics.The diagnosis of AKI is made based on a persons signs and symptoms, along with lab tests for serum creatinine and measurement of urine output. Other tests include urine microscopy and urine electrolytes. Renal ultrasound can be obtained when a postrenal cause is suspected. A kidney biopsy may be obtained when intrinsic renal AKI is suspected and the cause is unclear.AKI is seen in 10-15% of people admitted to the hospital and in more than 50% of people admitted to the intensive care unit (ICU). AKI may lead to a number of complications, including metabolic acidosis, high potassium levels, uremia, changes in body fluid balance, effects on other organ systems, and death.
A systematic review of the literature in 2008 demonstrated no difference in outcomes between the use of intermittent hemodialysis and continuous venovenous hemofiltration (CVVH) (a type of continuous hemodialysis). Among critically ill patients, intensive renal replacement therapy with CVVH does not appear to improve outcomes compared to less intensive intermittent hemodialysis. However, other clinical and health economic studies demonstrated that, initiation of CRRT is associated with a lower likelihood of chronic dialysis and was cost-effective compared with IRRT in patients with acute kidney injury. Complications
Metabolic acidosis, hyperkalemia, and pulmonary edema may require medical treatment with sodium bicarbonate, antihyperkalemic measures, and diuretics. Lack of improvement with fluid resuscitation, therapy-resistant hyperkalemia, metabolic acidosis, or fluid overload may necessitate artificial support in the form of dialysis or hemofiltration. However, oliguria during anesthesia may predict AKI, but the effect of a fluid load is highly variable. Striving toward a predefined urine output  target to prevent AKI is futile. Early recovery of AKI
AKI recovery can be classified into three stages 1–3 on the basis of the inverse of the AKI KDIGO serum creatinine criteria. Prognosis
Mortality
Mortality after AKI remains high. AKI has a death rate as high as 20%, which may reach up to 50% in the intensive care unit (ICU). Each year, around two million people die of AKI worldwide.AKI develops in 5% to 30% of patients who undergo cardiothoracic surgery, depending on the definition used for AKI.