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Prerenal azotemia

Azotemia - prerenal; Uremia; Renal underperfusion

 

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

Causes

 

Prerenal azotemia is common, especially 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

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 also can 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
  • Fast pulse
  • Fatigue
  • Pain in the belly
  • Pale skin color
  • Swelling
  • Thirst

 

Exams 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
  • 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 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.

 

 

References

Goldfarb DA, Poggio ED. Etiology, pathogenesis, and management of renal failure. In: Wein AJ, Kavoussi LR, Novick AC, et al., eds. Campbell-Walsh Urology. 10th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 43.

Meyer TW, Hostetter TH. The pathophysiology of uremia. In: Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector's The Kidney. 9th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 53.

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    Review Date: 11/26/2014

    Reviewed By: Charles Silberberg, DO, private practice specializing in nephrology; affiliated with New York Medical College, Division of Nephrology, Valhalla, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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