Acute tubular necrosis

Definition

Acute tubular necrosis is a kidney disorder involving damage to the renal tubule cells, resulting in acute kidney failure.

Causes, incidence, and risk factors

Acute tubular necrosis (ATN) is caused by ischemia of the kidneys (lack of oxygen to the kidney tissues), or by exposure to materials that are poisonous to the kidney (nephrotoxic agents).

The internal structures of the kidney, particularly the tissues of the kidney tubule, become damaged or destroyed. ATN is one of the most common structural changes associated with the development of acute renal failure.

ATN, along with prerenal azotemia are the most common causes of renal failure in hospitalized patients. Risks for acute tubular necrosis include injury or trauma with resulting damage to the muscles, recent major surgery, blood transfusion reaction, septic shock or other forms of shock, and severe hypotension (low blood pressure) that lasts longer than 30 minutes.

Any condition that causes a reduction in the amount of blood being pumped by the heart may cause ATN. Liver disease and damage caused by diabetes mellitus (diabetic nephropathy) may make a person more susceptible to the condition.

ATN can be caused by:

• Exposure to nephrotoxic agents such as aminoglycoside antibiotics
• Antifungal agents such as amphotericin
• Dye used for radiographic (x-ray) studies

Symptoms

• Urine output, decreased or none
• Generalized swelling, fluid retention
• Nausea, vomiting
• Decreased consciousness
  • Drowsy, lethargic, hard to arouse
  • Delirium or confusion
  • Coma

Note: Other symptoms of acute renal failure may also be present.

Signs and tests

Examination usually indicates acute renal failure. There may be signs of fluid overload, including abnormal sounds on listening to the heart and lungs with a stethoscope (auscultation).

• Urinalysis may show casts, renal tubular cells, and red blood cells.
• Urine sodium may be high.
• Fractional excretion of sodium and of urea may be relatively high.
• Urine specific gravity and osmolarity urine indicate dilute urine
• BUN and serum creatinine levels may increase.

A kidney biopsy may show acute tubular necrosis, but a biopsy is rarely performed.

Treatment

In most people, acute tubular necrosis is reversible. The goal of treatment is to prevent life-threatening complications of acute renal failure during the time the lesion is present.

Treatment focuses on preventing the excess accumulation of fluids and wastes while allowing the kidneys to heal. Observation for deterioration of kidney function should be ongoing.

Fluid intake may be restricted to a volume equal to the volume of urine produced.

The intake of substances that are normally excreted by the kidney may be restricted to minimize their buildup in the body. This may include a diet high in carbohydrates, low in protein, reduced sodium, and reduced potassium.

The underlying cause must be identified and treated.

Diuretics (water pills) may be used to increase fluid excretion from the kidney. Medications may be given to control potassium levels in the bloodstream.

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.

Decreased mental status, pericarditis, increased potassium levels, total lack of urine production, fluid overload, and uncontrolled accumulation of nitrogen waste products are common indications for dialysis.

Expectations (prognosis)

The duration of symptoms of ATN is variable. The decreased urine output phase may last from a few days to 6 weeks or more. This is occasionally followed by a period of high urine output, where the healed and newly refunctioning kidneys attempt to clear the body of fluid and wastes. One or two days after urine output rises, symptoms reduce and laboratory values begin to return to normal.

Complications

• Increased risk of infection
• Gastrointestinal loss of blood
• Chronic renal failure
• End-stage renal disease
• Hypertension

Calling your health care provider

Call your health care provider if urine output decreases or stops, or if other symptoms suggestive of acute tubular necrosis develop.

Prevention

Prompt treatment of conditions that can result in decreased blood flow and/or decreased oxygenation of the kidneys may reduce the risk of acute tubular necrosis.

Blood transfusions are crossmatched to reduce the risk of incompatibility reactions.

Disorders such as diabetes, liver disorders, or cardiac disorders must be controlled as much as possible to reduce the risk of ATN.

Exposure to medications that can be toxic to the kidney should be carefully monitored. Serum levels of the medication may be checked regularly. Adequate hydration after radiocontrast dyes may allow their excretion and reduce the risk of kidney damage.

Illustrations

Kidney anatomy

Kidney - blood and urine flow

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