section 12.3
Digestion and Absorption of Major Food Substances
TABLE 12-6
Abnormalities o f Lipid Digestion Due to Impaired Lipolysis
Type of Defect
Biochemical Disturbance
Examples of Disease States
Rapid gastric emptying
Reduction in the efficiency of
lipid interaction with bile and
pancreatic secretions
Gastrectomy, as in treatment
of ulcer or in neoplasms of stomach
Acidic duodenal pH
Inactivation of pancreatic lipase and
decreased ionization of bile acids
Zollinger-Ellison syndrome
Decreased CCK release
Congenital lipase or
colipase deficiency
Deficiency of bile and pancreatic
Defective lipolysis
Disorders associated with mucosal
destruction; regional enteritis, gluten
Pancreatic insufficiency
Defective lipolysis
Chronic pancreatitis, pancreatic duct
obstruction (e.g., cystic fibrosis)
Absent or decreased
bile salts
Decreased lipolysis due to impaired
micelle formation
(See Table 12-7)
other autoimmune disorders such as lupus and rheumatoid
arthritis, and relatives of patients with celiac disease.
The diagnosis of celiac disease includes characteristic
intestinal biopsy findings (discussed above) and serologi-
cal testing for antigliadin and antiendomysial antibodies.
The treatment of patients with celiac disease consists of
lifelong complete abstinence of gluten-containing foods,
acceptable foods are rice, potato, and maize.
Cystic fibrosis
(CF) is a disease of multiple exocrinopa-
thy and generalized malabsorption due to lack of delivery
TABLE 12-7
Abnormalities o f Lipid Digestion Due to Impaired
Micelle Formation Leading to Decreased Lipolysis
Type of Defect
Examples of Disease States
Decreased hepatic
synthesis of bile salts
Decreased delivery of
bile salts to the
intestinal lumen
Decreased effective
concentration of
conjugated bile acids
Increased intestinal loss
of bile salts
Severe parenchymal liver
Biliary obstruction due to
stone, tumor, or primary
biliary cirrhosis
Zollinger-Ellison syndrome
(causes hyperacidity);
bacterial overgrowth and
stasis; administration of
drugs, neomycin, and
Ileal disease or resection
of pancreatic digestive enzymes to the small intestine. CF
is an autosomal recessive disease and is due to lethal ho-
mozygous mutations. Among Caucasians the incidence
is 1 in 2000-3000 births. The prevalence of heterozygous
individuals is about 1 in 20. Abnormalities in affected per-
sons are found in airways, lungs, pancreas, liver, intestine,
vas deferens, and sweat glands. The primary abnormality
in CF is in electrolyte transport, specifically in Cl- secre-
tion from the apical membrane of the epithelial cells of
sweat glands, airways, pancreas, and intestine. Defective
Cl- secretion causes hyperactivity of Na+ absorption and
these two processes cause the secreted mucus to become
viscous and sticky. The most life-threatening clinical fea-
ture is related to pulmonary disease. The sticky, viscous
mucus clogs the airway and compromises the normal beat-
ing of the cilia that cover the apical surface of the airway
epithelium. These conditions encourage lung infections
by bacteria such as
Pseudomonas aeruginosa
lococcus aureus.
The clinical abnormalities related to the gastrointestinal
tract are not life-threatening and can be treated. In new-
borns with CF, intestinal obstruction (meconium ileus)
can occur in
1 0
2 0
% of cases due to failure of digestion of
intraluminal contents due to lack of pancreatic enzymes
in utero.
Exocrine pancreatic enzyme deficiency is present
from birth affecting both lipid and protein digestion. In
general, carbohydrate digestion is not severely impaired.
CF is associated with a plethora of clinical conditions
such as diseases of the heptobiliary tract and genitouri-
nary tract (e.g., male infertility). Elevation of chloride
concentration in the sweat is the most consistent functional
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