Health Encyclopedia

Prerenal azotemia

Definition

Prerenal azotemia is an abnormally high level of nitrogen-type wastes in the blood.

Alternative Names

Azotemia - prerenal; Uremia; Renal underperfusion

Causes, incidence, and risk factors

Prerenal azotemia is somewhat common, especially in people who are in the hospital.

The kidneys normally filter the blood. When the volume or pressure of blood flow through the kidney drops, blood filtration also drops, and may not occur at all. Waste products stay in the blood and little or no urine is formed, even though the kidney itself is intact and working.

Lab tests show that nitrogen-type wastes, such as creatinine and urea, build up in the body (azotemia). These waste products act as poisons when they build up. They damage tissues and reduce the ability of the organs to function. The build-up of nitrogen waste products and excess fluid in the body cause most of the symptoms of prerenal azotemia and acute kidney failure.

Prerenal azotemia is the most common form of kidney failure in hospitalized patients. Any condition that reduces blood flow to the kidney may cause it, including:

Burns
Conditions that allow fluid to escape from the bloodstream
Loss of blood volume (such as with dehydration)
Prolonged vomiting or diarrhea, bleeding

Conditions in which blood volume is not lost, but the heart cannot pump enough blood or the blood is pumped at low volume, also increase the risk for prerenal azotemia. These conditions include:

Heart failure
Shock (such as septic shock)

It also can be caused by conditions where the blood flow to the kidney is interrupted, such as:

Certain types of surgery
Renal artery embolism
Renal artery occlusion
Trauma to the kidney

Symptoms

Confusion
Decreased alertness
Decreased or no urine produced
Dry mouth
Fatigue
Pale skin color
Rapid pulse
Swelling
Thirst

Other symptoms may include:

Excessive urination at night
Pain in the abdomen

Signs and tests

An examination may show:

Collapsed neck veins
Dry mucus membranes
Little or no urine in the bladder
Low blood pressure
Low heart function or hypovolemia
Poor skin turgor
Rapid heart rate
Reduced pulse pressure (difference between systolic blood pressure and diastolic blood pressure)
Signs of acute kidney failure

The following tests may be done for prerenal azotemia:

Blood creatinine
BUN
Osmolality and specific gravity
Urine tests to check sodium and creatinine levels and to monitor kidney function

Treatment

The main goal of treatment is to quickly correct the cause before the kidney becomes damaged. People often need to stay in the hospital, and may need treatment in an intensive care unit. Treatment may include hemodialysis or dialysis inside the body (peritoneal dialysis).

Intravenous fluids, including blood or blood products, may be used to increase blood volume. After blood volume has been restored, medications may be used to increase blood pressure and heart output. These may include dopamine, dobutamine, and other heart medications. The cause of the decreased blood volume or blood pressure should be diagnosed and treated.

If the person has other symptoms of acute kidney failure, treatment for it should include medication, diet changes, or dialysis.

Expectations (prognosis)

Prerenal azotemia can be reversed if the cause can be found and corrected within 24 hours. However, if the cause is not fixed quickly, damage may occur to the kidney (acute tubular necrosis).

Complications

Acute kidney failure
Acute tubular necrosis (tissue death)

Calling your health care provider

Go to the emergency room or call the local emergency number (such as 911) if you have symptoms of prerenal azotemia.

Prevention

Quickly treating any condition that reduces the volume or force of blood flow through the kidneys may help prevent prerenal azotemia.

Review Date:2/7/2008
Reviewed By:Parul Patel, MD, Private Practice specializing in Nephrology and Kidney and Pancreas Transplantation, affiliated with California Pacific Medical Center, Department of Transplantation, San Francisco, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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