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Prerenal azotemia

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Azotemia - prerenal; Uremia; Renal underperfusion; Acute renal failure - prerenal azotemia

Definition

Prerenal azotemia is an abnormally high level of nitrogen waste products in the blood.

Causes

Prerenal azotemia is common, especially in older adults and in people who are in the hospital.

The kidneys filter the blood. They also make urine to remove waste products. When the amount, or pressure, of blood flow through the kidney drops, filtering of the blood also drops. Or it may not occur at all. Waste products stay in the blood. Little or no urine is made, even though the kidney itself is working.

When nitrogen waste products, such as creatinine and urea, build up in the body, the condition is called azotemia. These waste products act as poisons when they build up. They damage tissues and reduce the ability of the organs to function.

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

Burns
Conditions that allow fluid to escape from the bloodstream
Long-term vomiting, diarrhea, or bleeding
Heat exposure
Decreased fluid intake (dehydration)
Loss of blood volume
Certain medicines, such as ACE inhibitors (drugs that treat heart failure or high blood pressure) and NSAIDs

Conditions in which the heart cannot pump enough blood or pumps blood at a low volume also increase the risk for prerenal azotemia. These conditions include:

Heart failure
Shock (septic shock)

It can also be caused by conditions that interrupt blood flow to the kidney, such as:

Certain types of surgery
Injury to the kidney
Blockage of the artery that supplies blood to the kidney (renal artery occlusion)

Symptoms

Prerenal azotemia may have no symptoms. Or, symptoms of the causes of prerenal azotemia may be present.

Symptoms of dehydration may be present and include any of the following:

Confusion
Decreased or no urine production
Dry mouth due to thirst
Fast pulse
Fatigue
Pale skin color
Swelling

Exams and Tests

An examination may show:

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

The following tests may be done:

Blood creatinine
BUN
Urine 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.

Intravenous (IV) fluids, including blood or blood products, may be used to increase blood volume. After blood volume has been restored, medicines may be used to:

Increase blood pressure
Improve the pumping of the heart

If the person has symptoms of acute kidney failure, treatment will likely include:

Dialysis
Diet changes
Medicines

Outlook (Prognosis)

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

Possible Complications

Complications may include:

Acute kidney failure
Acute tubular necrosis (tissue death)

When to Contact a Medical Professional

Go to the emergency room or call 911 or the local emergency number 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.

References

Haseley L, Jefferson JA. Pathophysiology and etiology of acute kidney injury. In: Feehally J, Floege J, Tonelli M, Johnson RJ, eds. Comprehensive Clinical Nephrology. 6th ed. Philadelphia, PA: Elsevier; 2019:chap 66.

Okusa MD, Portilla D. Pathophysiology of acute kidney injury. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 28.

Wolfson AB. Renal failure. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 83.

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Review Date: 10/19/2022

Reviewed By: Walead Latif, MD, Nephrologist and Clinical Associate Professor, Rutgers Medical School, Newark, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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