<P> Acute kidney injury (AKI), previously called acute renal failure (ARF), is an abrupt loss of kidney function that develops within 7 days . </P> <P> Its causes are numerous . Generally it occurs because of damage to the kidney tissue caused by decreased kidney blood flow (kidney ischemia) from any cause (e.g., low blood pressure), exposure to substances harmful to the kidney, an inflammatory process in the kidney, or an obstruction of the urinary tract that impedes the flow of urine . AKI is diagnosed on the basis of characteristic laboratory findings, such as elevated blood urea nitrogen and creatinine, or inability of the kidneys to produce sufficient amounts of urine . </P> <P> AKI may lead to a number of complications, including metabolic acidosis, high potassium levels, uremia, changes in body fluid balance, and effects on other organ systems, including death . People who have experienced AKI may have an increased risk of chronic kidney disease in the future . Management includes treatment of the underlying cause and supportive care, such as renal replacement therapy . </P> <P> The clinical picture is often dominated by the underlying cause. The 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 . </P>

Differentiate among prerenal intrarenal and postrenal causes of acute renal failure