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Medicanet 
conditions and treatments
acute renal failure
Acute Renal Failure Types |
Acute Renal Failure TypesDepending on the cause of renal failure, Acute Renal Failure is classified into three types: prerenal, postrenal or intrinsic.
Prerenal ARF is caused by problems in blood supply and blood circulation or perfusion to the kidneys.
This results in the failure of the kidneys to filter the blood properly. Prerenal ARF patients are typically in a critical condition and experience very low blood pressure resulting in shock.
If the condition is not arrested, prerenal ARF may result to multiple organ failure due to underperfusion to other organs. Causes for prerenal ARF include hypotension or decrease in blood supply due to shock or dehydration, hepatorenal syndrome where circulation of the blood to the kidneys is adversely affected by liver failure and a number of preexisting medical conditions such as vascular problems such as atheroembolic disease or the hardening of the arteries due to fat deposits or renal vein thrombosis.
The second type of ARF is postrenal ARF.
In this condition, kidney failure is caused by an acute obstruction in the urinary tract that compromises the flow of urine out of both kidneys. Blockage in renal excretion creates pressure to build up in the tubular filtering unites that produce urine called renal nephrons.
High fluid pressure ultimately causes the nephrones to stop producing urine. The condition of kidney failure depends upon the level of obstruction in the kidneys.
This condition of postrenal ARF is oftentimes noticed in elderly men with enlarged prostrate glands which affect the health flow of urine. Usual causes of postrenal ARF include medication that may interfere with normal bladder processes, bladder obstruction that may be caused by enlarged prostate gland, bladder stones or prostate cancer, kidney stones in the ureters or the tubes where urine passes from the kidney to the bladder, obstructions in the end channels of the nephrons or tubule obstruction, malignancy in the abdomen caused by ovarian or colorectal cancer, injury caused to the kidney, an obstructed urinary catheter or retroperitoneal fibrosis.
Whenever ARF is neither prerenal or postrenal, the cause is considered to be renal or intrinsic, which means damage or injury is caused within both kidneys.
Some 40% of ARF cases are intrinsic ARF. Intrinsic ARF is usually caused by breakdown of muscle tissue or rhabdomyolysis causing the release of myoglobin in the blood which adversely affects the kidneys, hemolysis which is caused by the breakdown of red blood cells and infection in the kidneys usually sepsis or systematic inflammation of the kidneys due to infection called pyelonephritis. A major cause of intrinsic ARF, however is the accumulation of ischemia or toxins due to medications such as NSAIDs, aminoglycoside antibiotics, iodinated contrast and lithium. Ischemia reduces circulation of the blood to the kidneys which results in tissue death and irreversible kidney failure.
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