Acute renal failure (ARF)is an abrupt loss of kidney function that develops within 7 dayscaused by decreased kidney blood flow (kidney ischemia) from any cause (e.g., low blood pressure), exposure to toxin substances harmful to the kidney, an inflammatory process in the kidney (sepsis shock), or an obstruction of the urinary tract that impedes the flow of urine resulting in elevated blood urea nitrogen and creatinine, or inability of the kidneys to produce sufficient amounts of urine..