Webster's New World Medical Dictionary

portal hypertension
An elevated pressure in the
veins of the portal circulation. Normally, the veins
from the stomach, intestine, spleen, and pancreas
merge into the portal vein, which then branches into
smaller vessels and travels through the liver. If the
vessels in the liver are blocked, it is hard for the
blood to flow, causing high pressure in the portal
system. It can cause gastrointestinal bleeding,
ascites, and symptoms related to decreasing func-
tion of the liver.
portal vein
A large vein formed by the union of the
splenic and superior mesenteric veins. The portal
vein conveys venous blood to the liver for detoxifica-
tion before the blood is returned to circulation via the
hepatic veins.
port
-
wine stain
A mark on the skin whose rich,
ruby-red color resembles that of port wine. Due to
an abnormal aggregation of capillaries, a port-wine
stain is a type of hemangioma. It can occur on the
face as a sign of Sturge-Weber syndrome. See also
Sturge
-
Weber syndrome.
positive, false
See 
false positive.
positron emission tomography
See 
PET scan.
post
- Prefix meaning after.
posterior
The back. The opposite of posterior is
anterior. See also Appendix B, “Anatomic
Orientation Terms.”
posterior cruciate ligament
The cross-shaped
ligament that crosses behind the anterior cruciate
ligament and within the knee joint. Abbreviated PCL.
See also 
knee.
posterior pituitary
See 
pituitary, posterior.
posteroanterior
In anatomy, from back to front.
Abbreviated PA. For example, a chest X-ray taken
with the chest against the film plate and the X-ray
machine behind the patient is a PA view. The oppo-
site of posteroanterior is anteroposterior (AP). See
also Appendix B, “Anatomic Orientation Terms.”