Webster's New World Medical Dictionary

blood urea nitrogen
A measure of the urea
level in blood. Abbreviated BUN. Diseases that com-
promise the function of the kidney frequently lead to
increased BUN levels.
blood, urinary
See 
blood in the urine.
blood–brain barrier
A protective network of
blood vessels and cells that filters blood flowing to
the brain. The blood–brain barrier normally pre-
vents infectious agents and foreign substances from
getting into the brain. Medications designed to work
within the brain and spinal fluid must cross the
blood–brain barrier to be effective.
bloody nose
See 
nosebleed.
bloody show
Literally, the appearance of blood,
a classic sign of impending labor. The bloody show
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bloody show
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consists of blood-tinged mucus created by extrusion
and passage of the mucous plug that filled the cervical
canal during pregnancy.
bloody sputum
Coughed up blood or bloody
mucus. Bloody sputum can be caused by infection in
the lungs and airways, such as acute bronchitis or
pneumonia, or cancer. Whenever bloody sputum is
present and cannot be attributed to a curable infec-
tious condition, a complete lung evaluation is war-
ranted, including bronchoscopy, to be certain cancer
is not present. Also known as hemoptysis.
blot, Western
A technique in molecular biology
that is used to separate and identify proteins. It is
called a Western blot merely because it is similar to
a Southern blot, which was named after its inventor,
the British biologist M.E. Southern. For example,
the Western blot assay method is commonly used to
diagnose Lyme disease.