The kidneys filter waste products and toxins from the blood and maintain water balance in the body. To function normally, the kidneys require high-volume delivery of blood to be filtered, adequate tissue function and unobstructed outflow tracts for urine and filtered blood. Problems in any of these three areas can cause sudden-onset kidney failure--acute renal failure. People with acute renal failure (ARF) typically produce little or no urine and have high blood pressure and swelling in the extremities due to fluid retention.
Prerenal Acute Renal Failure
Prerenal ARF is the most common type of acute renal failure. The problem in prerenal ARF is inadequate blood flow to the kidneys, a condition known as renal hypoperfusion. A total body water deficit can lead to renal hypoperfusion and may be caused by conditions including severe bleeding, burns and massive vomiting or diarrhea. Heart failure and liver failure also may cause inadequate blood flow to the kidneys. Other possible causes include overwhelming infection with septic shock, atherosclerosis of the blood vessels leading to the kidneys, severe allergic reactions with shock and medications. In most cases, alleviating the underlying cause of prerenal acute renal failure leads to restoration of kidney function.
Postrenal Acute Renal Failure
Postrenal ARF, the least common type of acute renal failure, occurs when the urinary outflow tract or the blood outflow leaving the kidneys is obstructed. Urinary outflow tract obstruction causes include kidney stones, bladder stones, cancer, prostate enlargement and narrowing of the urethra (the tube for passing urine from the bladder to the outside). A blood clot or external compression due to a tumor are the most common causes of outflow obstruction of blood from the kidney.
Intrinsic Acute Renal Failure
Intrinsic ARF is caused by a problem with the kidneys. Ischemia--oxygen deprivation due to inadequate blood flow--is a common cause of intrinsic acute renal failure. In this situation, the problem is not the supply of blood to the kidneys for filtration, but rather the insufficiency of the blood supply to the kidney tissue itself. Blood clots, atherosclerotic plaques and inflammatory disorders of the blood vessels (vasculitis) can precipitate ischemic ARF. Toxins that damage the internal structures of the kidneys are another cause of intrinsic ARF. Common offending agents include platinum-based chemotherapy drugs, cyclosporine, aminoglycoside antibiotics, X-ray contrast dye, carbon tetrachloride and ethylene glycol. Infections and allergic reactions, especially due to medications, can cause intrinsic ARF. Nonsteroidal anti-inflammatory drugs (NSAIDs) and certain antibiotics and diuretics are the most common medications responsible for allergy-related ARF. Rejection of a transplanted kidney by the immune system typically presents as intrinsic ARF.
References
- "Harrison's Principles of Internal Medicine, 16th Edition"; Dennis L. Kasper, M.D., et al, Editors; 2004
- Merck Manual: Acute Renal Failure
- American Family Physician: Acute Renal Failure
- Mayo Clinic: Acute Kidney Failure, Causes
- MedlinePlus: Acute Kidney Failure
