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 person's 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. People who have experienced AKI are at increased risk of developing chronic kidney disease in the future. Management includes treatment of the underlying cause and supportive care, such as renal replacement therapy. Signs and symptoms The clinical presentation is often dominated by the underlying cause. The various symptoms of acute kidney injury result from the various disturbances of kidney function that are associated with the disease. Accumulation of urea and other nitrogen-containing substances in the bloodstream lead to a number of symptoms, such as fatigue, loss of appetite, headache, nausea, and vomiting. Marked increases in the potassium level can lead to abnormal heart rhythms, which can be severe and life-threatening. Fluid balance is frequently affected, though blood pressure can be high, low, or normal. Pain in the flanks may be encountered in some conditions (such as clotting of the kidneys' blood vessels or inflammation of the kidney). This is the result of