718
U N I T 8
Gastrointestinal and Hepatobiliary Function
surface of the intestine. They include disorders such as
celiac disease and Crohn disease. Disorders of lymphatic
transport interfere with the transport of absorbed lipids.
The process can be interrupted by congenital defects,
neoplasms, trauma, and selected infectious diseases.
Malabsorption Syndrome
In many malabsorption disorders one or more of the
intestinal absorptive processes predominate, but more
than one usually contributes to the manifestations of the
disorder. As a result, malabsorption syndromes resem-
ble each other more than they differ. Weakness, muscle
wasting, and weight loss occur despite normal or exces-
sive caloric intake.
General symptoms include diarrhea (from nutri-
ent malabsorption and intestinal secretion), flatu-
lence, bloating, abdominal cramps, and weight loss. A
hallmark of malabsorption is
steatorrhea,
characterized
by fatty, bulky, yellow-gray, and foul-smelling stools.
Along with loss of fat in the stools, there is failure to
absorb the fat-soluble vitamins. This can lead to easy
bruising and bleeding because of vitamin K deficiency,
as well as bone pain and a predisposition to the devel-
opment of fractures and tetany from vitamin D and cal-
cium deficiency. In addition, there may be macrocytic
anemia and peripheral neuropathy as a result of vitamin
B
12
deficiency. Table 29-2 describes the signs and symp-
toms of impaired absorption of dietary constituents.
Celiac Disease
Celiac disease, also known as
celiac sprue
and
gluten-
sensitive enteropathy,
is an immune-mediated disorder
triggered by ingestion of gluten-containing grains (wheat,
barley, and rye).
53–56
Until recently, celiac disease was
considered to be a rare malabsorption syndrome that
manifested during early childhood, but today it is known
TABLE 29-2
Sites of and Requirements for Absorption of Dietary Constituents and Manifestations of
Malabsorption
Dietary Constituent
Site of Absorption
Requirements
Manifestation
Water and electrolytes
Mainly small bowel
Osmotic gradient
Diarrhea
Dehydration
Cramps
Fat
Upper jejunum
Pancreatic lipase
Bile salts
Functioning lymphatic
channels
Weight loss
Steatorrhea
Fat-soluble vitamin deficiency
Carbohydrates
Starch
Small intestine
Amylase
Maltase
Isomaltase
α
-dextrins
Diarrhea
Flatulence
Abdominal discomfort
Sucrose
Small intestine
Sucrase
Lactose
Small intestine
Lactase
Maltose
Small intestine
Maltase
Fructose
Small intestine
Protein
Small intestine
Pancreatic enzymes
(e.g., trypsin, chymotrypsin,
elastin)
Loss of muscle mass
Weakness
Edema
Vitamins
A
Upper jejunum
Bile salts
Night blindness
Dry eyes
Corneal irritation
Folic acid
Duodenum and jejunum Absorptive; may be impaired
by some drugs (i.e.,
anticonvulsants)
Cheilosis
Glossitis
Megaloblastic anemia
B
12
Ileum
Intrinsic factor
Glossitis
Neuropathy
Megaloblastic anemia
D
Upper jejunum
Bile salts
Bone pain
Fractures
Tetany
E
Upper jejunum
Bile salts
Uncertain
K
Upper jejunum
Bile salts
Easy bruising and bleeding
Calcium
Duodenum
Vitamin D and parathyroid
hormone
Bone pain
Fractures
Tetany
Iron
Duodenum and jejunum Normal pH
(hydrochloric acid secretion)
Iron-deficiency anemia
Glossitis
