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The kidneys are a pair of organs which help regulate electrolyte balance, blood pressure, and acid-base balance, in addition to producing urine. Renal failure, also known as kidney failure, occurs when the kidneys cease functioning normally, usually due to disease or injury. Common symptoms include fluid retention, altered cognitive function, changes in urine output, and back pain.
There are two main categories of kidney failure: acute and chronic. Acute kidney failure is often the result of an event which interrupts the flow of blood to the kidneys. This may be caused by an accident or injury, or may be a result of surgical complications which reduce blood flow to the organs. Alternatively, acute kidney failure may be the result of toxicity caused by a drug overdose which overwhelms the ability of the organs to function normally.
Symptoms of acute renal failure often go unrecognized as being indicative of a serious health condition, and many patients are diagnosed only when they visit a doctor for an unrelated health problem. Symptoms can include swelling of the legs and feet, reduced urine output, increased thirst, rapid pulse, dizziness and nausea, vomiting or reduced appetite, and feelings of confusion, restlessness, or fatigue. Back pain may also be present, typically in the region below the ribcage and above the waist.
In contrast, chronic renal failure is usually caused by a chronic kidney disease that gradually reduces kidney function over the course of several years. The two most common causes of chronic kidney failure are diabetes mellitus and long-term uncontrolled high blood pressure. Genetic conditions such as polycystic kidney disease can also cause chronic kidney disease.
A person with chronic kidney failure experiences symptoms when renal function falls below a certain level. This level is defined by the glomerular filtration rate, which is an expression of how effectively the kidneys filter liquid. Symptoms usually appear around the point at which the glomerular filtration rate falls to 30% of its normal level, and may include personality changes, cognitive impairment, nausea or vomiting, anemia and easy bruising, and fluid retention. Fluid may be retained in the lungs or heart, causing difficulty breathing and chest pain. Very rarely, cognitive impairment may lead to seizures.
Chronic kidney failure is treated with dialysis, a process in which the blood is filtered to remove waste products. People with acute renal failure may also receive dialysis on a temporary basis until their kidneys resume normal function. For those with chronic renal failure, however, dialysis is required on a permanent basis unless a donor kidney can be successfully transplanted.