BLOOD

Urea nitrogen test



BLOOD:
" INTRODUCTION
" ROLE OF BLOOD
" COMPOSITION OF BLOOD
" Plasma
" Red Blood Cells
" Blood Type
" White Blood Cells
" Platelets and Clotting
" PRODUCTION AND ELIMINATION OF BLOOD CELLS
" Red Blood Cell Diseases
" White Blood Cell Diseases
" Coagulation Diseases
" BLOOD BANKS
" Blood Transfusion
" Blood Count
" Blood donation and registry
" Blood gas analysis
" Blood sugar tests
" Blood typing and crossmatching
" Blood urea nitrogen test
" Blood-viscosity reducing drugs
Circulatory System:
" INTRODUCTION
" COMPONENTS OF THE CIRCULATORY SYSTEM
" OPERATION AND FUNCTION
" Systemic Circulation
" Pulmonary Circulation
" Additional Functions
" Blood Pressure
" DISEASES AND DISORDERS
" HEART
Vasculature System:
" Arteries
" Veins
" Capillaries
" Vasculature of the Arm
" Vasculature of the Head
" Vasculature of the Leg
" Vasculature of the Torso

Definition

The blood urea nitrogen (BUN) test measures the level of urea nitrogen in a sample of the patient's blood. Urea is a substance that is formed in the liver when the body breaks down protein. Urea then circulates in the blood in the form of urea nitrogen. In healthy people, most urea nitrogen is filtered out by the kidneys and leaves the body in the urine. If the patient's kidneys are not functioning properly or if the body is using large amounts of protein, the BUN level will rise. If the patient has severe liver disease, the BUN will drop.

Purpose

The BUN level may be checked in order to assess or monitor:

the presence or progression of kidney or liver disease.

blockage of urine flow.

mental confusion. Patients with kidney failure are sometimes disoriented and confused.

abnormal loss of water from the body (dehydration).

recovery from severe burns. The body uses larger than normal amounts of protein following serious burns.

Description

The BUN test is performed on a sample of the patient's blood, withdrawn from a vein into a vacuum tube. The procedure, which is called a venipuncture, takes about five minutes.

Preparation

The doctor should check to make sure that the patient is not taking any medications that can affect BUN results. These drugs include the antibiotics chloramphenicol, streptomycin, amphotericin B, methicillin, gentamicin, tobramycin, and kanamycin, as well as diuretics and corticosteroids.

The patient should be advised not to eat large amounts of meat the day before the test.

Aftercare

Aftercare consists of routine care of the area around the venipuncture.

Risks

The primary risk is the possibility of a bruise or swelling in the area of the venipuncture. The patient can apply moist warm compresses.

Normal results

Normal BUN levels are 5-18 mg/dL for children; 7-18 mg/dL for adults; and 8-20 mg/dL in the elderly.

Abnormal results

BUN levels can be too low as well as too high.

Abnormally low BUN

Low levels of BUN may indicate overhydration, malnutrition, celiac disease [a disease characterized by the inability ot tolerate foods containing wheat protein (gluten)], liver damage or disease, or use of corticosteroids. Low BUN may also occur in early pregnancy.

Abnormally high BUN

High levels of BUN may indicate kidney disease or failure; blockage of the urinary tract by a kidney stone or tumor; a heart attack or congestive heart failure; dehydration; fever; shock; or bleeding in the digestive tract. High BUN levels can sometimes occur during late pregnancy or result from eating large amounts of protein-rich foods. A BUN level higher than 100 mg/dL points to severe kidney damage.

Key Terms

Urea
A compound containing nitrogen that occurs in the urine and other body fluids as a result of protein metabolism.

World Health Organization

Blood Clot in the Legs

Deep venous thrombosis (DVT) refers to a blood clot embedded in one of the major deep veins of the lower legs, thighs, or pelvis. A clot blocks blood circulation through these veins, which carry blood from the lower body back to the heart. The blockage can cause pain, swelling, or warmth in the affected leg.

Next: Blood Clot in the Legs

Blood Culture

A blood culture is done when a person has symptoms of a blood infection, also called bacteremia. Blood is drawn from the person one or more times and is tested in a laboratory to find and identify any microorganism present and growing in the blood. If a microorganism is found,...

Next: Blood Culture