Acute tubular necrosis

Definition

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

Alternative Names

Necrosis - renal tubular; ATN; Necrosis - acute tubular

Causes, incidence, and risk factors

Acute tubular necrosis (ATN) is caused by lack of oxygen to the kidney tissues (ischemia of the kidneys).

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 that can lead to acute renal failure.

ATN is one of the most common causes of kidney failure in hospitalized patients. Risks for acute tubular necrosis include:

• Blood transfusion reaction
• Injury or trauma that damages the muscles
• Recent major surgery
• Septic shock or other forms of shock
• Severe low blood pressure (hypotension) that lasts longer than 30 minutes

Liver disease and kidney damage caused by diabetes (diabetic nephropathy) may make a person more susceptible to the condition.

ATN can be caused by:

• Exposure to medications that are toxic to the kidneys (such as aminoglycoside antibiotics)
• Antifungal agents (such as amphotericin)
• Dye used for x-ray (radiographic) studies

Symptoms

• Decreased consciousness
  • Coma
  • Delirium or confusion
  • Drowsy, lethargic, hard to arouse
• Decreased urine output or no urine output
• General swelling, fluid retention
• Nausea, vomiting

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

Signs and tests

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

Other signs include:

• BUN and serum creatinine levels may increase
• Fractional excretion of sodium and of urea may be relatively high
• Kidney biopsy may show acute tubular necrosis (but a biopsy is rarely done)
• Urinalysis may show casts, kidney tubular cells, and red blood cells
• Urine sodium may be high
• Urine specific gravity and osmolarity urine indicate dilute urine

Treatment

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

Treatment focuses on preventing the excess build-up of fluids and wastes, while allowing the kidneys to heal. Patents should be watched for deterioration of kidney function.

Treatment can include:

• Identifying and treating the underlying cause of the problem
• Restricting fluid intake to a volume equal to the volume of urine produced
• Restricting substances normally removed by the kidneys (such as protein, sodium, potassium) to minimize their buildup in the body
• Taking medications to help control potassium levels in the bloodstream
• Taking water pills (diuretics) to increase fluid removal from the kidney

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

Dialysis may be needed in the following cases:

• Decreased mental status
• Fluid overload
• Increased potassium levels
• Pericarditis
• Total lack of urine production
• Uncontrolled buildup of nitrogen waste products

Expectations (prognosis)

The duration of symptoms varies. 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 functioning kidneys try 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

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

Calling your health care provider

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

Prevention

Promptly treating conditions that can lead to decreased blood flow and/or decreased oxygen to the kidneys can reduce the risk of acute tubular necrosis.

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

Control conditions such as diabetes, liver disorders, and cardiac disorders to reduce the risk of acute tubular necrosis.

Carefully monitor exposure to medications that can be toxic to the kidney. Have your blood levels of these medications checked regularly. Drink a lot of fluids after having any radiocontrast dyes to allow them to be removed from the body and reduce the risk of kidney damage.

References

Goldman L, Ausiello D. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders; 2007 Chapter 121