Webster's New World Medical Dictionary

peritoneum
The membrane that lines the
abdominal cavity and covers most of the abdominal
organs.
peritonitis
Inflammation of the peritoneum, the
membrane that lines the inner wall of the abdomen
and pelvis. Peritonitis can result from infection, as
by bacteria or parasites; injury and bleeding; or dis-
eases, such as systemic lupus erythematosus. See
also 
peritonitis, acute; peritonitis, chronic.
peritonitis, acute
Sudden inflammation of the
peritoneum that results in abrupt abdominal pain
(acute abdomen). The most serious causes of acute
peritonitis include perforation of the esophagus,
stomach, duodenum, gallbladder, bile duct, bowel,
appendix, colon, rectum, and bladder; trauma;
intestinal obstruction; pancreatitis; vascular catas-
trophes (mesenteric thrombosis or embolism); and
as an infectious complication of peritoneal dialysis
and pelvic inflammatory disease.
peritonitis, chronic
Longstanding inflammation 
of the peritoneum. Causes of chronic peritonitis
include repeated attacks of infection such as from
pelvic inflammatory disease, foreign substances
such as talc, and chronic infections within the
abdomen such as tuberculosis.
peritonsillar abscess
A collection of pus
behind the tonsils that pushes one of the tonsils
toward the uvula. A peritonsillar abscess is generally
very painful and is usually associated with a
decreased ability to open the mouth. If left
untreated, the infection can spread deep in the
neck, causing airway obstruction and life-threaten-
ing complications.
pernicious anemia
See 
anemia, pernicious.
pernicious vomiting of pregnancy
See 
hyper-
emesis gravidarum.
personality disorder
A disorder characterized
by the long-standing use of mechanisms of coping in
an inappropriate, stereotyped, and maladaptive
manner. Personality disorders are enduring and
persistent styles of behavior and thought, not atypi-
cal episodes. The personality disorders encompass
a group of behavioral disorders that are different
and distinct from the psychotic and neurotic disor-
ders. The official psychiatric manual, the DSM-IV,
defines a personality disorder as an enduring pat-
tern of inner experience and behavior that differs
markedly from the expectations of the individual’s
culture, is pervasive and inflexible, has an onset in