pyloric sphincterThe valve at the base
of the stomachthat controls movement
of food into the duodenum.
pyloric stenosisNarrowing 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 ulceror stomach
cancer. Babies start projectile vomiting
(profuse vomiting in which the stomach
contents may be ejected several feet) 2–5
weeks after birth. Ultrasoundscanningis
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.
pyloroplastyAn 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 gangrenosumA rare con-
dition characterized by ulcers, usually
on the legs, that turn into hard, painfulPYLORIC SPHINCTER areas surrounded by discoloured skin.
Pyoderma gangrenosum occurs as a
rare complication in ulcerative colitis.
pyogenic granulomaA common, non-
cancerousskin tumour that develops on
exposed areas after minor injury. It can
be removed surgically, by electrocautery,
or by cryosurgery.
pyrazinamideA drug sometimes used
to treat tuberculosis. Possible adverse
effects are nausea, joint pains, gout,
and liver damage.
pyrexiaA medical term for fever.
pyrexia of uncertain originPersis-
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
lymphoma; and collagen diseases, such
as systemic lupus erythematosusand
temporal arteritis. Another possible cause
is a drugreaction.
pyridoxineVitamin B 6 (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.
pyrimethamineA drug that is used in
combination with other drugs to treat
resistant malaria.
pyrogenA substance that produces
fever. The term is usually applied to
proteins released by white blood cellsin
response to infections. The word is also
sometimes used to refer to chemicals
released by microorganisms.
pyromaniaA 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.
pyuriaThe presence of white blood cells
in the urine, indicating infection of a
kidney or urinary tract infectionand
inflammation.PYLORIC SPHINCTER PYURIAP
LOCATIONSTRUCTURE
OF SPHINCTERDuodenumStomachOesophagusPyloric sphincterStomachStomachDuodenum