at present the three-year success rate is about 50
percent.
The small intestine produces numerous DIGES-
TIVE ENZYMESand DIGESTIVE HORMONESnecessary for
proper function of the entire gastrointestinal tract.
One challenge with small bowel transplantation is
the restoration of this production. Another chal-
lenge is the abundance of lymphatic tissue in the
intestinal mucosa (mucous membrane that lines
the inside of the small intestine). Researchers do
not yet fully understand the role of this tissue,
called GUT-ASSOCIATED LYMPHOID TISSUE(GALT). How-
ever, GALT appears to intensify the IMMUNE
RESPONSEtypical with transplanted organs, requir-
ing large doses of IMMUNOSUPPRESSIVE MEDICATIONS
such as cyclosporine. These medications suppress
immune activity throughout the body, not only in
the intestinal tract, resulting in significant risk for
INFECTION. Up to a third of people who receive
small bowel transplantation experience complica-
tions including organ rejection and infection dur-
ing the first year.
See also CYSTIC FIBROSIS; GASTROENTERITIS; ORGAN
TRANSPLANTATION.
small intestine The segment of the gastrointesti-
nal tract immediately following the STOMACH. The
small intestine’s three sections—DUODENUM,
JEJUNUM, and ILEUM—perform about 85 percent of
the digestive functions of the gastrointestinal tract.
Food passes from the STOMACHto the duodenum,
from the duodenum to the jejunum, and from the
jejunum to the ileum. The small intestine loops
and folds through the inner abdomen, with the
COLON(large intestine) encircling it like a frame.
Microscopic extensions, villi, arise from the
mucosa, forming peaks and valleys that dramati-
cally increase the surface area of the mucosa.
CONDITIONS THAT CAN AFFECT THE SMALL INTESTINEBOWEL ATRESIA CELIAC DISEASE
Crohn’s disease GASTROENTERITIS
ILEUS LACTOSE INTOLERANCE
MALABSORPTION PEPTIC ULCER DISEASE
WHIPPLE’S DISEASE
A meal’s transit time through the 18 or so feet of
the small intestine is about 10 hours, during which
intestinal mucosa (mucous membrane that lines
the intestinal tract) extracts all of the nutrients,
many of the electrolytes, and much of the water.
For further discussion of the small intestine
within the context of gastrointestinal structure
and function, please see the overview section “The
Gastrointestinal System.”
See also ANUS; FOOD-BORNE ILLNESSES; INFLAMMA-
TORY BOWEL DISEASE(IBD); IRRITABLE BOWEL SYNDROME
(IBS); RECTUM.steatohepatitis Fatty deposits throughout the
LIVER, also called fatty liver, that create irritation
and INFLAMMATION. Doctors believe steatohepatitis
represents a malfunction of the body’s lipid pro-
cessing and transfer mechanisms, many of which
take place in the liver. Steatohepatitis is common
with long-term ALCOHOLuse and ALCOHOLISM(alco-
holic steatohepatitis). It also occurs without alco-
hol involvement (nonalcoholic steatohepatitis),
notably with DIABETES(which alters lipid METABO-
LISM) and OBESITY.
The most common form of steatohepatitis,
called macrovesicular because the fatty deposits
are large, may not show symptoms. Rather, the
doctor may detect it during physical examination
as HEPATOMEGALY(enlarged LIVER). When symptoms
are present they reflect noninfectious HEPATITIS:
JAUNDICE(yellow discoloration of the SKIN), tender-
ness or PAINin the upper right abdomen, fatigue,
NAUSEA, and loss of APPETITE. LIVER FUNCTION TESTS
may be inconclusive; ULTRASOUND or COMPUTED
TOMOGRAPHY(CT) SCANoften reveals the fatty accu-
mulations. PERCUTANEOUS LIVER BIOPSYconfirms the
diagnosis. The form of steatohepatitis associated
with alcoholism, obesity, and diabetes is macro-
vesicular.
Steatohepatitis occasionally manifests as an
acute illness with significant symptoms and rapid
progression to clotting dysfunction (coagulopathy)
and neurologic involvement (hepatic NEUROPATHY).
This form of steatohepatitis, called microvesicular
because the fatty deposits are small, can be fatal
without appropriate supportive treatment until
the liver recovers.
Macrovesicular steatohepatitis generally does
not require treatment though treating any underly-
ing condition helps restore normal lipid metabolism
with the result that fatty acids move out of the liver.
When alcohol consumption is a factor, steatohep-steatohepatitis 89