ENLmedical.com: Conditions And Concerns: Medical Encyclopedia: Acute tubular necrosis

Acute tubular necrosis

Causes and Risks:
Acute tubular necrosis (ATN) is caused by ischemia of the kidneys (lack of oxygen to the 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 occurs in about 4 out of 10,000 people. 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 predispose a person to the condition. ATN can be caused by exposure to nephrotoxic agents such as aminoglycoside antibiotics, antifungal agents such as amphotericin, medications to prevent rejection of transplanted organs such as cyclosporine, dye used for radiographic studies, and other substances.

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 .

Symptoms:

urine output, decreased or none
urination, excessive volume
urination, excessive at night
generalized swelling , fluid retention
nausea , vomiting
consciousness, decreased
- drowsy , lethargic , hard to arouse
- delirium or confusion
- coma
seizures
easy bruising or bleeding
vomiting blood
stools, bloody
decrease in sensation , especially the hands or feet
chills shaking
abnormal urine color
blood in the urine
joint pain
flank pain

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, 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.
The ratio of urine to plasma (blood) levels of creatinine and urea may be reduced.
BUN and serum creatinine levels may increase.

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

This disease may also alter the results of the following tests:

Treatment:
In most people, acute tubular necrosis is a reversible lesion. 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 protein in diet , reduced sodium in diet , and reduced amount of potassium in diet .

The underlying cause must be identified and treated.

Diuretics may be used to increase the excretion of fluid 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.

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
damage to the heart or nervous system
chronic renal failure
end-stage renal disease
hypertension

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

The kidneys are responsible for removing wastes from the body, regulating electrolyte balance and blood pressure, and the stimulation of red blood cell production. The gross anatomical structure of the kidney is illustrated.

This is the typical appearance of the blood vessels (vasculature) and urine flow pattern in the kidney. The blood vessels are shown in red and the urine flow pattern in yellow.