Prerenal azotemia is relatively common, especially in hospitalized patients. The kidneys normally filter the blood. When the volume or pressure of blood flow through the kidney drops, blood filtration also drops drastically, and may not occur at all. Waste products remain in the bloodstream and little or no urine is formed, even though the internal structures of the kidney are intact and functional.
Lab tests show that nitrogen-type wastes, such as creatinine and urea, are accumulating in the body (azotemia). These waste products act as poisons when they accumulate, damaging tissues and reducing the ability of organs to function. The build-up of nitrogen waste products and accumulation of excess fluid in the body are responsible for most of the symptoms of prerenal azotemia and acute renal failure.
Prerenal azotemia is the most common form of kidney failure seen in hospitalized patients. Any condition that reduces blood flow to the kidney may cause it -- including loss of blood volume, which may occur with dehydration, prolonged vomiting or diarrhea, bleeding, burns, and other conditions that allow fluid to escape from circulation. Conditions where the volume is not lost, but where the heart cannot pump enough blood, or the blood is pumped at low volume, also increase risk for prerenal azotemia. These conditions include shock (such as septic shock), heart failure, and conditions where the blood flow to the kidney is interrupted, such as trauma to the kidney, surgery of various types, renal artery embolism, and other types of renal artery occlusion.
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