Encyclopedia of Health and Medicine

20 The Gastrointestinal System
reaction that converts the unconjugated bilirubin
to conjugated bilirubin, which then becomes an
ingredient of BILE.
Bilirubin is yellow and in turn colors the bile yellow;
hence its designation as a bile pigment. Intestinal
BACTERIA further metabolize bilirubin, the major
component of which is urobilinogen. Urobilinogen
gives the feces their characteristic dark color. Pale
feces are a hallmark of disturbances of bilirubin
METABOLISM. Increased bilirubin levels in the blood
result in JAUNDICE, a yellowish discoloration of the
SKIN most visible in the SCLERA (“white” of the EYE).
Certain wavelengths of light on the skin help the
body complete bilirubin metabolism.
See also CIRRHOSIS; HEPATITIS; PHOTOTHERAPY.
biliary dysfunction
See GALLBLADDER DISEASE.
borborygmus The growling and rumbling sound
of gas moving through the gastrointestinal tract during
digestion. Borborygmus, sometimes referred to
in the plural, borborygmi, indicates normal function
of the gastrointestinal system. The sounds originate
with the STOMACH and continue through the SMALL
INTESTINE and large intestine. Excessive rumblings
may indicate incomplete digestion such as may
result from eating too rapidly or eating too much at
one time. Some people experience an increase in
borborygmus when they are hungry.
See also BOWEL SOUNDS; FLATULENCE.
bowel atresia A CONGENITAL ANOMALY in which
there is incomplete development of the intestinal
tract, typically with closures and “dead ends” that
block flow through the intestines. The intestines
may be entangled or intussuscepted (one segment
of bowel telescopes into another), presenting
grave risk for tissue death (necrosis). Nearly
always the diagnosis is apparent within hours of
birth because the infant is unable to eat and the
abdomen quickly becomes distended. VOMITING
BILE is a key indicator of intestinal obstruction of
some sort. Bowel atresia is more common in premature
infants. The most common locations for
bowel atresia are the DUODENUM (duodenal atresia)
and the JEJUNUM and ILEUM (jejunoileal atresia).
Bowel atresia is life-threatening and requires
emergency surgery to correct the defects.
See also ANAL ATRESIA; CONGENITAL HEART DISEASE;
ESOPHAGEAL ATRESIA; INTUSSUSCEPTION.
bowel movement The passage of solid digestive
waste (called feces or stool) from the body through
the ANUS. The frequency, appearance, and nature of
bowel movements are highly variable. Food typically
travels through the gastrointestinal system in
18 to 36 hours, so most people have bowel movements
daily or every other day. However, “normal”
is an individual pattern that correlates to dietary
habits, physical activity level, and lifestyle and can
range from three bowel movements a day to one
bowel movement every three days. What can
become significant from a health standpoint are
deviations from an individual’s pattern of bowel
movements. Short-term changes in bowel patterns
may result from eating different foods, viral INFEC-
TION (GASTROENTERITIS or ENTERITIS), inadequate fluid
consumption, and medications. A shift in bowel
patterns not due to intentional actions such as
dietary or exercise change may indicate health conditions
that require medical evaluation.
See also BOWEL SOUNDS; CONSTIPATION; DIARRHEA.
bowel sounds The noises of the gastrointestinal
tract. Listening to bowel sounds through a stethoscope
(AUSCULTATION) provides important clues
about the function of the gastrointestinal tract.
Normal bowel sounds vary in tone and loudness
according to the activity of the bowel though follow
characteristic patterns the doctor can identify.
Excessive bowel sounds often accompany excessive
bowel activity such as DIARRHEA, GASTROENTERI-
TIS, and flare-ups of INFLAMMATORY BOWEL DISEASE
(IBD). Reduced bowel sounds occur when bowel
activity slows, such as between meals or when
there is an intestinal obstruction. Narcotic medications
and anesthetic agents also slow bowel function,
and reduced bowel sounds may persist for
several days after surgery. The absence of bowel
sounds signals a nonfunctioning bowel, which can
be due to intestinal obstruction or, in an infant, a
gastrointestinal atresia. The absence of bowel
sounds may be a sign of a medical emergency that
requires surgical intervention.
See also BORBORYGMUS; BOWEL ATRESIA; ESOPHA-
GEAL ATRESIA.