Acute kidney failure

Definition

Acute renal failure is sudden loss of the ability of the kidneys to excrete wastes, concentrate urine, and conserve electrolytes. ("Acute" means sudden, "renal" refers to the kidneys.)

Causes, incidence, and risk factors

The kidneys filter wastes and excrete fluid by using the bloodstream's own natural pressure. There are numerous potential causes of damage to the kidneys:

• Decreased blood flow -- this may occur when there is extremely low blood pressure caused by trauma, complicated surgery, septic shock, hemorrhage, or burns; associated dehydration; or other severe or complicated illnesses.
• Acute tubular necrosis (ATN) -- may occur when tissues aren't getting enough oxygen or when the renal artery is blocked or narrowed (see acute arterial occlusion of the kidney and renal artery stenosis).
• Over-exposure to metals, solvents, radiographic contrast materials, certain antibiotics, and other medications or substances.
• Myoglobinuria (myoglobin in the urine) -- this condition may be caused by rhabdomyolysis, alcohol abuse, a crush injury, tissue death of muscles from any cause, seizures, and other disorders.
• Direct injury to the kidney.
• Infections such as acute pyelonephritis or septicemia.
• Urinary tract obstruction, such as a narrowing of the urinary tract (stricture), tumors, kidney stones, nephrocalcinosis or enlarged prostate with subsequent acute bilateral obstructive uropathy.
• Severe acute nephritic syndrome.
• Disorders of the blood, such as idiopathic thrombocytopenic purpura (ITP), transfusion reaction, or other hemolytic disorders, malignant hypertension and disorders resulting from childbirth, such as bleeding placenta abruptio or placenta previa can damage the kidneys.
• Autoimmune disorders such as scleroderma can cause acute renal failure.
• In young children, hemolytic uremic syndrome is an increasingly common cause of acute renal failure. A toxin-secreting bacterium, Escherichia coli, found in contaminated undercooked meats, has been implicated as the cause of hemolytic uremic syndrome.

Symptoms

• decreased urine output
  • decreased urine volume (oliguria)
  • no urine output (anuria)
• urination, excessive at night (can occur in some types of renal failure)
• ankle, feet, and leg swelling
• generalized swelling, fluid retention
• decrease in sensation, especially the hands or feet
• decreased appetite
• metallic taste in mouth
• persistent hiccups
• changes in mental status or mood
  • agitation
  • drowsiness, lethargy
  • delirium or confusion
  • coma
  • fluctuating mood
  • difficulty paying attention (attention deficit)
  • hallucinations
• slow, sluggish, movements
• seizures
• hand tremor
• nausea, vomiting
  • may persist for days
  • morning sickness
  • vomiting blood
• prolonged bleeding, bruising easily
  • stools, bloody
  • nosebleed
  • growth, slow (child 0-5 years)
• flank pain
• fatigue
• ear noise/buzzing
• breath odor
• breast development in males
• blood pressure, high

Signs and tests

Examination and testing can reveal acute renal failure and help rule out other disorders that affect kidney function. In this condition, there is generalized swelling caused by fluid retention.

With a stethoscope, a heart murmur or other sounds related to increased fluid volume may be heard and crackles may be heard from the lungs. Also, if inflammation of the heart lining (pericarditis) is present, a pericardial friction rub may be heard with a stethoscope over the heart.

Lab values may change suddenly (within a few days to 2 weeks):

• Urinalysis may be abnormal.
• Serum creatinine may increase by 2 mg/dL or more over a 2-week period.
• Creatinine clearance may be decreased.
• BUN may increase suddenly.
• Serum potassium levels may be increased.
• Arterial blood gas and blood chemistries may show metabolic acidosis.
• Kidney or abdominal ultrasound is usually the best test, but abdominal X-ray, abdominal CT scan or abdominal MRI may also reveal the cause of acute renal failure. Kidney size is usually normal or slightly large.
• Chemical tests of blood and urine may also help to distinguish the causes. A clean catch urine specimen will indicate if the cause is infection within the urinary tract. Renal angiography (renal arteriography) may be used to diagnose causes within the blood vessels of the kidney.

• 25-hydroxy Vitamin D
• amylase
• amylase, urine
• AST
• calcium (ionized)
• CO2
• creatinine - urine
• ESR
• nerve conduction velocity
• platelet aggregation test
• protein electrophoresis - urine
• RBC indices
• RT3U
• serum calcium
• serum chloride
• serum phosphorus
• serum sodium
• sodium, urine
• T4
• urea nitrogen; urine
• uric acid
• urinary casts
• urine 24h volume
• urine concentration test
• urine pH
• urine specific gravity

Treatment

The goal of treatment is to identify and treat any reversible causes of the kidney failure (e.g., use of kidney-toxic medications, obstructive uropathy, volume depletion). Treatment also focuses on preventing excess accumulation of fluids and wastes, while allowing the kidneys to heal and gradually resume their normal function. Hospitalization is required for treatment and monitoring.

Your fluid intake may be severely restricted to an amount equal to the volume of urine you produce. You may be given specific dietary modifications to reduce build-up of toxins normally handled by the kidneys, including a diet plan high in carbohydrates and low in protein, salt, and potassium.

Antibiotics may be used to treat or prevent infection. Diuretics may be used to remove fluid from the kidney.

A major priority in treatment is to control dangerous hyperkalemia (increased blood potassium levels). A variety of different medications may be used, including IV (intravenous) calcium, glucose/insulin, and oral or rectal administration of potassium exchange resin (Kayexalate).

Dialysis may be used to remove excess waste and fluids. This often makes the person feel better and may make the kidney failure easier to control. Dialysis may not be necessary for all people, but is frequently lifesaving, particularly if serum potassium is dangerously high.

Common symptoms that require the use of dialysis include decreased mental status, pericarditis, increased potassium levels, total lack of urine production, fluid overload, and uncontrolled accumulation of nitrogen waste products (serum creatinine > 10 mg/dl and BUN > 120 mg/dl).

Support Groups

The stress of having an illness can often be helped by joining a support group where members share common experiences and problems. See kidney disease - support group. Your local hospital or dialysis center may also have information regarding local support groups.

Expectations (prognosis)

Although acute renal failure is potentially life-threatening and may require intensive treatment, it usually reverses within several weeks to a few months after the underlying cause has been treated.

A few people will progress to chronic renal failure and/or end-stage renal disease. Death is most common when the cause of the kidney failure is related to surgery or trauma or when it occurs in people with coexisting heart disease, lung disease or recent stroke. Old age, infection, loss of blood from the GI (gastrointestinal) tract, and progression of the kidney failure also increase the risk of death.

Complications

• increased risk of infections
• gastrointestinal loss of blood
• chronic renal failure
• end-stage renal disease
• damage to the heart or nervous system
• hypertension (high blood pressure)

Calling your health care provider

Call your health care provider if decreased urine output or other symptoms indicate the possibility of acute renal failure.

Prevention

Treating any causative disorders may help to prevent acute renal failure. Many cases may not be preventable.

Illustrations

Kidney anatomy

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