Renal failure refers to a condition in which the kidneys lose the ability to perform their basic function of filtering blood, with reabsorption of useful substances and elimination of metabolic waste products and other toxins through urine.
The most common form of kidney failure is chronic renal failure, which gradually sets in over the years, usually in people already suffering from other chronic conditions that also secondarily damage the kidneys, such as hypertension or diabetes.
Mostly people over 65 years old are affected.
Acute renal failure, on the other hand, is an abrupt phenomenon that can result in total loss of kidney function within a few days, often proving fatal; almost always, it affects critically ill patients, usually already admitted to intensive care units, or people who accidentally take substances that are very toxic to the kidneys. In all cases, it requires highly specialized emergency interventions, which are beyond the scope of this discussion.
