Celiac Disease (cont.)
What does celiac disease do to the small intestine?
The small intestine has an inner lining of cells that form finger-like
projections called villi. The villi are important because they increase the
number of cells and surface area available for the absorption of nutrients from
the intestinal lumen into the blood stream. In celiac disease, the inflammation
destroys the villi, causing the inner lining of the small intestine to become
flattened. This loss of villi reduces the cells and surface area available for
absorption of nutrients. The impaired absorption of nutrients is referred to as
malabsorption. The malabsorption of nutrients leads to nutrient deficiencies,
referred to as malnutrition.
The length (amount) of the small intestine affected by the loss of villi
varies from patient to patient, and the length that is involved determines the
severity of signs and symptoms. Thus, patients whose entire small intestine is
affected by a loss of villi have more severe signs and symptoms of malabsorption
than patients who have only part of the small intestine affected. When only part
of the small intestine is affected, it usually is the upper small intestine (the
duodenum and jejunum) that is more affected than the lower small intestine (the
ileum).
What are the signs and symptoms of celiac disease?
Depending on the degree of malabsorption, the signs and symptoms of celiac disease
vary among individuals, ranging from no symptoms, few or mild signs and
symptoms, to many or severe signs and symptoms. There are two categories of
signs and symptoms: 1) signs and symptoms due to malabsorption, and 2) signs and
symptoms due to malnutrition including vitamin and mineral deficiencies.
1. Signs and symptoms of malabsorption
The three major categories of dietary nutrients are carbohydrates, proteins,
and fat. Absorption of all of these nutrients can be reduced in celiac disease;
however, fat is the most commonly and severely affected nutrient. Most of the
gastrointestinal symptoms and signs
of celiac disease are due to the inadequate absorption of fat (fat malabsorption).
Gastrointestinal symptoms of fat malabsorption include diarrhea, malodorous flatulence (foul smelling gas),
abdominal bloating, and increased amounts of fat in the stool (steatorrhea). The
unabsorbed fat is broken down by intestinal bacteria into
fatty acids, and these
fatty acids promote secretion of water into the intestine, resulting in
diarrhea. Fatty stools typically are large in volume, malodorous (foul
smelling), greasy, light tan or light grey in color, and tend to float in the
toilet bowl. Oil droplets (undigested fat) also may be seen floating on top of
the water.
Loss of intestinal villi also causes malabsorption of
carbohydrates, particularly the sugar lactose. Lactose is the primary sugar in milk. Lactose is
made up of two smaller sugars, glucose and galactose. In order for lactose to
be absorbed from the intestine and into the body, it must first be split into
glucose and galactose. The glucose and galactose then can be absorbed by the
cells lining the small intestine. The enzyme that splits lactose into glucose
and galactose is called lactase, and it is located on the
surface of the small intestinal villi. In celiac disease the intestinal villi
along with the lactase enzymes on their surface are destroyed, leading to malabsorption of lactose.
Signs and symptoms of malabsorption of lactose are
particularly prominent in individuals with celiac disease who have underlying lactose intolerance, a
genetically determined reduction in the activity of lactase. Symptoms of
lactose malabsorption (diarrhea, excessive flatulence (passing
gas), abdominal pain and abdominal
bloating or distension) occur because unabsorbed lactose passes through the
small intestine and into the colon. In the colon, there is a normal bacterium
that contains lactase and is able to split the lactose, using the resulting
glucose and galactose for its own purposes. Unfortunately, when they split the
lactose into glucose and galactose, the bacteria also release gas (hydrogen and
/or methane). A proportion of the gas is expelled and is responsible for the
increased flatus (passing
gas) that may occur in celiac disease. Increased gas mixed in the stool is
responsible for stool floating in the toilet bowl.
Not all of the lactose that reaches the colon is split
and used by colonic
bacteria. The unsplit lactose that reaches the colon causes water to be drawn
into the colon (by osmosis). This promotes diarrhea.
2. Signs and symptoms of malnutrition and vitamin or mineral deficiencies
Symptoms of malnutrition and vitamin or mineral
deficiencies include: weight loss, fluid retention, anemia, osteoporosis,
bruising easily, peripheral neuropathy (nerve damage), infertility, and muscle
weakness.
- Weight loss and fluid retention: Weight loss is the direct result of
inadequate absorption of carbohydrates, proteins and fat. However, weight loss
may not always occur because patients with celiac disease often have enormous
appetites that compensate for the reduced absorption of nutrients. Moreover,
weight loss can be masked by fluid retention. Fluid retention occurs in advanced
malnutrition because the reduced absorption of protein results in low protein
levels in the blood. High protein levels in the blood are necessary to keep
fluid from leaking out of blood vessels and into the body's tissues. When
blood protein levels fall as in celiac disease, fluid leaks into many tissues
(edema) but particularly the ankles
and feet, which swell due to the edema.
- Anemia: Lack of absorption of vitamin B12 and iron can lead to
anemia.
- Osteoporosis: Lack of absorption of vitamin D and calcium can lead to
osteoporosis and bone fractures.
- Easy bruising: Lack of absorption of vitamin K can lead to diminished
ability of blood to clot and hence to easy bruising or excessive bleeding.
- Peripheral neuropathy (nerve damage): Vitamin deficiencies of B12 and
thiamine may contribute to nerve damage with symptoms of poor balance, muscle weakness, and
numbness and tingling in the arms and legs.
- Infertility: Untreated celiac disease can lead to infertility in women, lack of
menses (menstruation), spontaneous
abortions and low birth weight infants.
- Muscle weakness: Lack of absorption and low levels of potassium
and magnesium can lead to severe muscle weakness, muscle cramps, and numbness or
tingling sensations in the arms and legs.
Next: How do symptoms of celiac disease differ with age of onset? »
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