Encyclopedia of Health and Medicine

18 The Gastrointestinal System
esophageal adenocarcinoma also has Barrett’s
esophagus.
Diagnosis of Barrett’s esophagus requires endoscopic
biopsy of the esophageal lining. Altered tissue
often appears reddened in endoscopic
visualization, though appearance cannot make the
diagnosis as GERD also can cause INFLAMMATION
and irritation of the esophageal lining that causes
it to appear reddened. A person who has confirmed
Barrett’s esophagus should undergo periodic
endoscopic biopsy as a measure to detect
further changes in the tissue (dysplasia) that could
indicate a developing cancer. Esophageal adenocarcinoma
appears to develop slowly, with a
period of years during which the tissue changes
are transitional. Dysplasia or cancer requires
appropriate treatment, which varies according to
individual health circumstances. There are no
treatments for Barrett’s esophagus or to prevent its
conversion to esophageal adenocarcinoma.
See also CANCER RISK FACTORS; ENDOSCOPY;
ESOPHAGEAL CANCER; ESOPHAGITIS.
bezoar A hardened mass of indigestible matter
that forms in the STOMACH, such as HAIR (trichobezoar),
insoluble plant fiber (phytobezoar), or a
combination of hair and plant fiber (trichophytobezoar).
Bezoars can develop in children who
chew their hair or eat substances such as sand or
grass and in adults who have slowed gastrointestinal
motility, such as might occur with GASTROPARE-
SIS or ACHALASIA. A bezoar can remain undetected
in the stomach for months, until it becomes large
enough to block the passage of food into the SMALL
INTESTINE. Common symptoms include PAIN, NAU-
SEA, VOMITING, and occasionally a palpable lump.
BARIUM SWALLOW or ENDOSCOPY can confirm the
diagnosis. Surgery (endoscopic or open) to remove
the bezoar is often the only treatment, as by the
time a bezoar causes symptoms it is too large to
pass through the gastrointestinal tract. Bezoars
may recur when the behavior responsible for their
development, such as hair chewing, persists.
See also ILEUS.
bile A liquid that the LIVER produces to carry some
of its waste products into the digestive tract. Specialized
cells called hepatocytes synthesize bile from
water, cholesterol, bile acids, bile salts, BILIRUBIN and
other bile pigments, and electrolytes. The hepatocytes
break down cholesterol, a fatty acid, into bile
acids. Other cells in the liver further convert bile
acids into water-soluble forms called bile salts.
The SPLEEN is the body’s scavenger and one of
its jobs is to remove old erythrocytes (red BLOOD
cells) from the blood and break them down. One
of the byproducts of this process is heme, the iron
compounds. After further metabolism one derivative
of heme is bilirubin. Bilirubin is dark yellow
and is the primary pigment in bile, giving bile its
dominant yellow coloration. Other bile pigments
come from substances the liver detoxifies from the
blood, adding to the bile’s color.
A network of BILE DUCTS collects bile from the
liver and carries it to the GALLBLADDER. The walls of
the gallbladder absorb about 90 percent of the
water the bile contains, producing a greatly concentrated
solution that the gallbladder ejects during
digestion to aid in digesting fatty foods. Bile that
enters the intestinal tract that the body does not
need for digestion continues to travel through the
intestines, eventually mixing with fecal matter for
excretion from the body. The liver secretes about
750 milliliters (roughly a quart) of bile every day.
See also ERYTHROCYTE; CHOLESTEROL BLOOD LEVELS;
GALLBLADDER DISEASE; PANCREATITIS.
bile ducts Channels that carry BILE from LIVER to
the GALLBLADDER and from the gallbladder to the
DUODENUM (first segment of the SMALL INTESTINE).
The intrahepatic ducts are within the structure of
the liver. They collect bile the liver secretes and
transport it from the liver. The extrahepatic ducts
are outside the liver and route bile to the gallbladder
and duodenum. They are
• the hepatic duct, which carries bile out of the
liver to the cystic duct
• the cystic duct, which carries bile from the
hepatic duct to the gallbladder and from the
gallbladder to the common duct
• the common duct, which carries bile into the
duodenum
The health conditions most likely to involve the
bile ducts are BILIARY ATRESIA, a CONGENITAL ANOMALY
in which the bile ducts form incompletely or not at
all, and ductal occlusion resulting from cholelithia-