Renal failure

Renal failure or kidney failure is a situation in which the kidneys fail to function adequately. It is divided in acute and chronic forms; either form may be due to a large number of other medical problems.

Biochemically, it is typically detected by an elevated serum creatinine. In the science of physiology, renal failure is described as a decrease in the glomerular filtration rate. When the kidneys malfunction, problems frequently encountered are abnormal fluid levels in the body, deranged acid levels, abnormal levels of potassium, calcium, phosphate, and (in the longer term) anemia. Long-term kidney problems have significant repercussions on other diseases, such as cardiovascular disease.

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Classification

Renal failure can broadly be divided into two categories: acute renal failure and chronic kidney disease.

The type of renal failure (acute vs. chronic) is determined by the trend in the serum creatinine. Other factors which may help differentiate acute and chronic kidney disease include the presence of anemia and the kidney size on ultrasound. Long-standing, i.e. chronic, kidney disease generally leads to anemia and small kidney size.

Acute renal failure

Main article: Acute renal failure

Acute renal failure (ARF) is, as the name implies, a rapidly progressive loss of renal function, generally characterized by oliguria (decreased urine production, quantified as less than 400 mL per day in adults,^[1] less than 0.5 mL/kg/h in children or less than 1 mL/kg/h in infants); body water and body fluids disturbances; and electrolyte derangement. An underlying cause must be identified to arrest the progress, and dialysis may be necessary to bridge the time gap required for treating these fundamental causes. ARF can result from a large number of causes.

Chronic kidney disease

Main article: Chronic kidney disease

Chronic kidney disease (CKD) can either develop slowly and show few initial symptoms, be the long term result of irreversible acute disease or be part of a disease progression. There are many causes of CKD. The most common cause is diabetes mellitus. Stage 1 CKD is mildly diminished renal function, with few overt symptoms. Stage 5 CKD is a severe illness and requires some form of renal replacement therapy (dialysis or renal transplant).

Acute on chronic renal failure

Acute renal failure can be present on top of chronic renal failure. This is called acute-on-chronic renal failure (AoCRF). The acute part of AoCRF may be reversible and the aim of treatment, as with ARF, is to return the patient to their baseline renal function, which is typically measured by serum creatinine. AoCRF, like ARF, can be difficult to distinguish from chronic renal failure, if the patient has not been monitored by a physician and no baseline (i.e., past) blood work is available for comparison.

Use of the term uremia

Before the advancement of modern medicine, renal failure was often referred to as uremic poisoning. Uremia was the term used to describe the contamination of the blood with urine. Starting around 1847, this term was used to describe reduced urine output, that was thought to be caused by the urine mixing with the blood instead of being voided through the urethra.^{[citation needed]} The term uremia is now used to loosely describe the illness accompanying kidney failure.^[2]

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