LOCATION
P
pyloric sphincter The valve at the base
of the
stomach
that controls movement
of food into the
duodenum
.
pyloric stenosis
Narrowing of the pyl-
orus (the lower outlet from the stomach),
which obstructs the passage of food
into the
duodenum
.
Pyloric stenosis
occurs in babies due to thickening of the
pyloric muscle, and in adults due to
scarring from a
peptic ulcer
or
stomach
cancer
.
Babies start projectile vomiting
(profuse vomiting in which the stomach
contents may be ejected several feet) 2-5
weeks after birth.
Ultrasound scanning
is
needed to confirm the diagnosis. In
adults, diagnosis may be made by a
bar-
ium X-ray examination
and
gastroscopy
.
In infants, surgical treatment involves
making an incision along the thickened
muscle. In adults, surgery is carried out
to correct the underlying cause.
pyloroplasty
An operation in which the
pylorus (the outlet from the stomach) is
widened to allow free passage of food
into the intestine. Pyloroplasty may be
performed as part of the surgery for a
peptic ulcer
, or to prevent tightening of
the pyloric muscles after
vagotomy
.
pyo-
A prefix that denotes a relationship
to
pus
.
The prefix py- is also used.
pyoderma gangrenosum
A rare con-
dition characterized by ulcers, usually
on the legs, that turn into hard, painful
PYURIA
areas surrounded by discoloured skin.
Pyoderma gangrenosum occurs as a
rare complication in
ulcerative colitis.
pyogenic granulom a A common, non-
cancerous skin tumour that develops on
exposed areas after minor injury. It can
be removed surgically, by
electrocauterys,
or by
cryosurgery.
pyrazinam ide A drug sometimes used
to treat
tuberculosis.
Possible adverse
effects are nausea, joint pains,
gout,
and liver damage,
p yrexia A medical term for
fever.
p yrexia o f un certain orig in Persis-
tent fever with no apparent cause. The
cause is usually an illness that is diffi-
cult to diagnose or a common disease
that presents in an unusual way. These
illnesses include various viral infec-
tions;
tuberculosis;
cancer, particularly
lymiphoma;
and
collagen diseases,
such
as
systemic lupus erythematosus
and
temporal arteritis.
Another possible cause
is a
drug
reaction.
pyridoxine
Vitamin B6 (see
vitamin B
complex
).
Dietary deficiency of this vita-
min is very rare but can be induced by
some drugs. Pyridoxine (50 to 100 mg
per day) is sometimes used to treat
pre-
menstrual syndrome
.
pyrimethamine
A drug that is used in
combination with other drugs to treat
resistant
malaria
.
pyrogen
A substance that produces
fever
. The term is usually applied to
proteins released by white
blood cells
in
response to infections. The word is also
sometimes used to refer to chemicals
released by microorganisms.
pyromania
A
persistent
impulse
to
start fires. The disorder is more often
diagnosed in males, and may be associ-
ated with a low IQ, alcohol abuse, and a
psychosexual disorder
.
pyuria
The presence of white
blood cells
in the
urine
, indicating infection of a
kidney
or
urinary tract infection
and
inflammation.
474
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