Kidney failure has many possible causes. Some lead to a rapid decline in kidney function (acute kidney injury Acute Kidney Injury Acute kidney injury is a rapid (days to weeks) decline in the kidneys’ ability to filter metabolic waste products from the blood. Causes include conditions that decrease blood flow to the kidneys... read more , also called acute renal failure). Others lead to a gradual decline in kidney function (chronic kidney disease Chronic Kidney Disease Chronic kidney disease is a slowly progressive (months to years) decline in the kidneys’ ability to filter metabolic waste products from the blood. Major causes are diabetes and high blood pressure... read more , also called chronic renal failure). In addition to the kidneys being unable to filter metabolic waste products (such as creatinine and urea nitrogen) from the blood, the kidneys are less able to control the amount and distribution of water in the body (fluid balance About Body Water Water accounts for about one half to two thirds of an average person’s weight. Fat tissue has a lower percentage of water than lean tissue and women tend to have more fat, so the percentage... read more ) and the levels of electrolytes Overview of Electrolytes More than half of a person's body weight is water. Doctors think about water in the body as being restricted to various spaces, called fluid compartments. The three main compartments are Fluid... read more (sodium, potassium, calcium, phosphate) and acid Overview of Acid-Base Balance An important part of being healthy is for the blood to maintain a normal degree of acidity or alkalinity. The acidity or alkalinity of any solution, including blood, is indicated on the pH scale... read more in the blood.
When kidney failure has lasted for some time, blood pressure often rises. The kidneys lose their ability to produce sufficient amounts of a hormone (erythropoietin) that stimulates the formation of new red blood cells, resulting in a low red blood cell count (anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more ). The kidneys also lose their ability to produce sufficient calcitriol (the active form of vitamin D), which is vital to bone health. In children, kidney failure affects the growth of bones. In both children and adults, kidney failure can lead to weaker, abnormal bones.
Although kidney function can decline in people of all ages, both acute kidney injury and chronic kidney disease are more common in older than in younger people. Many disorders that cause a decline in kidney function can be treated, and kidney function may recover. The availability of dialysis Dialysis Dialysis is an artificial process for removing waste products and excess fluids from the body, a process that is needed when the kidneys are not functioning properly. There are a number of reasons... read more and kidney transplantation Kidney Transplantation Kidney transplantation is the removal of a healthy kidney from a living or recently deceased person and then its transfer into a person with end-stage kidney failure. (See also Overview of Transplantation... read more has transformed kidney failure from a fatal disease to one that is manageable.