What is azotemia?

Azotemia is when there is a higher than normal concentration of urea in the blood or other nitrogen containing compounds. Urea is a waste product of the liver resulting from the metabolism of proteins. 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, then filtering of the blood also drops, or it may not occur at all. Waste products stay in the blood and little or no urine is made, even though the kidney itself is working. When nitrogen waste products, such as that of creatinine and urea, build up in the body, then this condition is known as azotemia. These waste products act as poisons when they build up, and hence they damage tissues and reduce the ability of the organs to function properly.

Azotemia is the most common form of kidney failure present with most hospitalized patients. Anything that may reduce the amount of blood flow to the kidney can cause azotemia, and this includes the following; loss of blood volume, heat exposure, conditions that allow fluid to escape from the bloodstream, decreased fluid intake (known as dehydration), diarrhea, long term vomiting, and bleeding. Heart failure and shock (such as that of septic shock) can cause the heart to not pump enough blood to the body, or it will pump blood at low levels, which in turn increases the risk for azotemia. Azotemia can also be caused by conditions that interrupt blood flow to the kidney, such as that of injury to the kidney itself, certain types of surgery which may affect blood flow to the kidney, and blockage of the artery that supplies blood to the kidney (such as that of renal artery occlusion).

There are a couple of signs and symptoms that a patient may have azotemia, those are; decreased or absent urine output, fatigue, decreased alertness, confusing, thirst, dry mouth (xerostomia), rapid pulse (tachycardia), swelling (edema or anasarca), pain in the belly, and pale skin color.

Why measure the level of blood urea nitrogen?

Measuring the level of blood urea nitrogen (BUN) can be helpful to examining if there is proper kidney function. Urea nitrogen is what forms when protein breaks down in the body. Normal human adult blood should contain anywhere between 6 to 20 mg of urea nitrogen per every 100 ml (6 to 20mg/dL) of blood. This however varies between laboratories. Having higher than normal levels may be due to congestive heart failure, excessive protein levels in the gastrointestinal tract, gastrointestinal bleeding, hypovolemia, heart attack, kidney diseases (including those of glomerulonephritis, pyelonephritis, and acute tubular necrosis), kidney failure, shock, and urinary tract obstruction in the body. Lower than normal levels may be caused because of liver failure, low protein diet, malnutrition, and over hydration. However for people with liver disease, the level of blood urea nitrogen may be low even if the kidneys are functioning normally.

Standard of preparation

Sampling is usually done in the morning in the hospital. There are no special preparations needed for this test. The doctor will advise and recommend if you need to be fasting prior to the blood examination. You should inform your doctor of any medication you are taking prior to the exam, as some medical treatments may interfere with the blood results.

Is the examination painful or dangerous?

The examination is neither painful nor dangerous. The patient may feel a tingling sensation with the entrance of the needle in the arm when blood is being extracted for examination.

How is the exam performed?

The exam consists of a simple blood sample test.