Acute kidney failure is a rapid (days to weeks) decline in the kidneys' ability to filter metabolic waste products from the blood. Acute kidney failure can result from any condition that decreases the blood supply to the kidneys, any disease affecting the kidneys themselves, or any condition that obstructs urine flow anywhere along the urinary tract. In many people, no cause of acute kidney failure can be identified. Kidney failure develops only if both kidneys are affected. Cause Underlying Problem Insufficient blood supply to the kidneys Blood loss Loss of large amounts of sodium and fluid Physical injury that blocks blood vessels Inadequate pumping of the heart (heart failure) Extremely low blood pressure (shock) Liver failure (hepatorenal syndrome) Injury to the kidneys Blood supply to the kidneys decreased long enough to damage the kidneys Toxic substances (for example, drugs, radiopaque dyes used in imaging tests, and poisons) Allergic reactions (for example, to certain antibiotics) Disorders affecting the filtering units (nephrons) of the kidneys (for example, acute glomerulonephritis, tumors damaging the kidneys, or vascular injury as occurs with hemolytic-uremic syndrome, systemic lupus erythematosus [lupus], atheroembolic kidney disease, Goodpasture's syndrome ,Wegener's granulomatosis, or polyarteritis nodosa) Obstructed urine flow Enlarged prostate Tumor pressing on the urinary tract Stones Obstruction within the kidneys (for example, by stones such as oxalate or uric acid) Symptoms Symptoms depend on the severity of kidney failure, its rate of progression, and its cause. In some people, the first symptom of acute kidney failure is water retention, with swelling of the feet and ankles or puffiness of the face and hands. People may pass cola-colored urine, which may indicate a number of kidney diseases. The amount of urine (which for most healthy adults is between 3 cups [about 750 milliliters] and 2 quarts [about 2 liters] per day) often decreases to less than 2 cups (about 500 milliliters) per day or stops completely. Very little urine production is called oliguria, and no urine production is called anuria. However, some people with acute kidney failure continue to produce normal amounts of urine. As acute kidney failure persists and metabolic waste products accumulate in the body, people may experience fatigue, a decreased ability to concentrate on mental tasks, loss of appetite, nausea, and overall itchiness (pruritus). People with acute kidney failure may experience a rapid heart rate (tachycardia) and light-headedness. If the cause is an obstruction, the backup of urine within the kidneys causes the drainage system to stretch (a condition called hydronephrosis). Urinary obstruction often produces a constant dull ache under the lower ribs but may produce crampy pain—ranging from mild to excruciating—usually along the sides (flanks) of the body. Some people with hydronephrosis have blood in their urine. If the obstruction is located below the bladder, the bladder will enlarge. If the bladder enlarges rapidly, people are likely to feel severe pain in the pelvis, just above the pubic bone. If the bladder enlarges slowly, pain may be minimal, but the lower part of the abdomen may swell because of the markedly distended bladder. If acute kidney failure develops during hospitalization, the condition often relates to some recent injury, surgery, drug, or illness such as infection. The symptoms of the cause of the acute kidney failure may predominate. For example, high fever, life-threatening low blood pressure (shock), and symptoms of heart failure or liver failure may occur before symptoms of kidney failure and be more obvious and urgent. Some of the conditions that cause acute kidney failure also affect other parts of the body. For example, Goodpasture's syndrome or Wegener's granulomatosis, which damages blood vessels in the kidneys, may also damage blood vessels in the lungs, causing a person to cough up blood. Rashes are typical of some causes of acute kidney failure, including polyarteritis nodosa, systemic lupus erythematosus, and some toxic drugs. Diagnosis Blood tests that measure levels of creatinine and urea nitrogen in the blood are needed to confirm the diagnosis. A progressive daily rise in creatinine indicates acute kidney failure. The level of creatinine is also the best indicator of the degree or severity of kidney failure. The higher the level, the more severe the failure is likely to be. Other blood tests detect metabolic imbalances that occur as kidney failure persists, such as an increase in blood acidity (acidosis, which causes a low bicarbonate level), a high potassium level (hyperkalemia), a low sodium level (hyponatremia), and a high phosphorus level (hyperphosphatemia). The physical examination findings may help doctors identify the cause of the acute kidney failure. For example, enlarged or tender kidneys may indicate obstruction with hydronephrosis. Urine tests, such as a urinalysis and measurement of certain electrolytes, may enable doctors to determine whether the cause of kidney failure is insufficient blood flow to the kidneys, damage to the kidneys, or urinary obstruction. Imaging of the kidneys using ultrasonography or computed tomography (CT) is helpful, sometimes by identifying hydronephrosis or an enlarged bladder. Imaging can also reveal the size of the kidneys. X-rays of the arteries or veins that lead to and from the kidneys (angiography) may be done if obstruction of blood vessels is the suspected cause. However, angiography is done only when other tests do not provide enough information, because angiography uses radiopaque dye (contrast agent) that contains iodine, which carries a risk of additional kidney damage. Magnetic resonance imaging (MRI) can provide the same type of information. However, MRI has traditionally used gadolinium, a substance that rarely causes a disorder that triggers production of scar tissue in the body (nephrogenic fibrosing dermopathy). Thus, MRI is now less likely to be used. If other tests do not reveal the cause of kidney failure, a biopsy may be necessary to determine the diagnosis and the prognosis. Prognosis Acute kidney failure and its immediate complications, such as water retention, high acid and potassium levels in the blood, and increased urea nitrogen in the blood, can often be treated successfully. The overall survival rate is about 60%. Survival is less than 50% for people who have several organs failing at the same time. Yet, survival is about 90% for people whose kidney failure is due to decreased blood flow because body fluids have been lost through bleeding, vomiting, or diarrhea—conditions that are reversible with treatment. Treatment Any treatable cause of kidney failure is treated as soon as possible. For example, if obstruction is the cause, a catheter (a tube placed into the bladder), endoscopy, or surgery may be needed to relieve the obstruction. Often, the kidneys can heal themselves, especially if the kidney failure has existed for less than 5 days and there are no complicating problems such as infection. During this time, measures are taken to prevent kidney failure from causing serious problems. Such measures may include the following: Doctors strictly limit the intake of all substances that are eliminated through the kidneys, including a large number of drugs. Salt (sodium) and potassium intake is usually restricted. Fluid intake is restricted to replacing the amount lost from the body, unless fluid is needed because there is too little blood flowing to the kidneys. Weight is measured every day because a change in weight is a good indicator of whether there is too much or too little water in the body. A healthy diet is provided to people whose condition allows them to eat. Moderate amounts of protein are acceptable, typically 0.8 to 1 grams per kilogram of body weight (0.4 to 0.5 grams per pound). Sodium polystyrene sulfonate is sometimes given by mouth or rectally to treat a high level of potassium in the blood. Calcium salts ( calcium carbonate Fluids are not restricted in people who are recovering from acute kidney failure caused by obstruction. During the recovery period, the kidneys are unable to reabsorb sodium and water normally, and a large amount of urine is produced for a period of time after the obstruction is relieved. During recovery, people may also need replacement of fluids and electrolytes, such as sodium, potassium, and magnesium. Acute kidney failure may be prolonged, necessitating removal of waste products and excess water. Waste removal can be done through dialysis, usually hemodialysis (seeDialysis: Hemodialysis). If kidney failure is predicted to be prolonged, dialysis is started as soon as possible after diagnosis. Dialysis may be needed only temporarily, until the kidneys recover their function, usually in several days to several weeks. If the kidneys are too badly damaged to recover, then the acute kidney failure becomes chronic.
Major Causes of Acute Kidney Failure Did You Know...
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Saturday, April 3, 2010
Labels: Acute Kidney Failure
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