27/12/2012
Acute Kidney Failure
Acute kidney failure is a rapid deterioration in the ability of kidneys to excrete waste and water from the body.
This occurs in about 5% of people who are hospitalized for any reason. It is even more common in those in ICU.
Causes of acute kidney failure fall into one of the following categories:
Prerenal failure
Prerenal failure is the most common type of acute renal failure (60%-70% of all cases). The kidneys do not receive enough blood to filter. Prerenal failure can be caused by the following conditions:
• Dehydration: – From vomiting, diarrhea, water pills, or blood loss
• Disruption of blood flow to the kidneys from a variety of causes:
o Severe fall in blood pressure in surgery with blood loss, severe injury or burns, or infection in the bloodstream (sepsis)
o Blockage or narrowing of a blood vessel carrying blood to the kidneys
o Heart failure or heart attacks causing low blood pressure
o Liver failure causing changes in hormones that affect blood flow and pressure to the kidney
There is no actual damage to the kidneys initially and with appropriate treatment, the failure usually can be reversed. Prolonged decrease in the blood flow to the kidneys, can lead to permanent damage to the kidney tissues.
Postrenal failure
Postrenal failure is sometimes referred to as obstructive renal failure, since it is often caused by something blocking elimination of urine produced by the kidneys. It is the rarest cause of acute kidney failure (5%-10% of all cases). This problem can be reversed, unless the obstruction is present long enough to cause damage to kidney tissue.
Obstruction of one or both ureters can be caused by the following:
• Kidney stone: usually only on one side
• Cancer of the urinary tract organs or structures near the urinary tract that may obstruct the outflow of urine
• Medications
Obstruction at the bladder outlet can be caused by the following:
• Bladder stone
• Enlarged prostate (the most common cause in men)
• Blood clot
• Bladder cancer
• Neurologic disorders of the causing a weakened bladder.
Treatment consists of relieving the obstruction. Once the blockage is removed, the kidneys usually recover in one to two weeks if there is no infection or other problem.
Primary Renal damage
This is the most complicated cause of renal failure (accounts for 25%-40% of cases). Renal causes of acute kidney failure include those affecting the filtering function of the kidney, those affecting the blood supply within the kidney, and those affecting the kidney tissue that handles salt and water processing.
Some kidney problems that can cause kidney failure include:
• Blood vessel diseases
• Blood clot in a vessel in the kidneys
• Injury to kidney tissue and cells
• Glomerulonephritis
• Acute interstitial nephritis
• Acute tubular necrosis
Glomerulonephritis: The glomeruli, the initial filtration system in the kidney, can be damaged by a variety of diseases, including infections. The resulting inflammation impairs kidney function.
• A common example is strep throat. Streptococcal bacterial infections may damage the glomeruli.
• Glomerular disorder symptoms may include dark-colored urine (like cola or tea) and back pain.
• Other symptoms include producing less urine than usual, blood in the urine, high blood pressure, and body swelling (retaining water).
• Treatment usually consists of medications and, if kidney function fails significantly, dialysis may be needed to remove life-threatening waste products that cannot be excreted.
Acute interstitial nephritis: This is a sudden decline in kidney function caused by inflammation of interstitial kidney tissue which primarily handles salt and water balance rather than the filtering of wastes.
• Medications such as antibiotics, anti-inflammatory medicines (for example, aspirin, ibuprofen).
• Other causes include infections and immune-related diseases such as lupus, leukemia, lymphoma, and sarcoidosis.
• It is usually reversible if the kidney damage is not severe.
• Treatment consists of withdrawal of offending drugs, treatment of infection, and dialysis in cases of very low kidney function.
Acute tubular necrosis: The kidney tubules are damaged and do not function normally. Tubular necrosis is usually the end result from the other causes of acute renal failure. The tubules are delicate structures that handle much of the kidney’s filtration function. When there is necrosis, the cells that form the tubules become dysfunctional and “die”.
• This condition accounts for 90% of cases of primary acute kidney failure.
• Causes include shock (decreased blood supply to the kidneys), drugs (especially antibiotics) and chemotherapy agents, toxins and poisons, and dyes used in certain kinds of x-rays.
• Some people produce much less urine than usual. Other symptoms of acute tubular necrosis include tiredness, swelling, lethargy, nausea, vomiting, abdominal pain, loss of appetite, and rash. Sometimes there are no symptoms.
• Treatment depends on the cause of the damage and may consist of discontinuing problem medications, replenishing body fluids, and improving blood flow to the kidney. A diuretic may be given to increase urine production if the total body water level is too high. Medications may be given to correct blood chemistry imbalances.
• If there is no recovery of the patient’s kidneys and these treatments do not sufficiently substitute for the lost kidney function, the patient will need regular dialysis or may be a candidate for kidney transplantation.
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Nephrology deals mainly with everything to do with the kidneys including Chronic Kidney Disease (CKD), Polycystic Kidney Disease (PKD), acute renal failure, and high blood pressure and are educated on all aspects of kidney transplantation and dialysis.
