Malabsorption

1. MALABSORPTION
 Malabsorption syndromes include a number of different
clinical manifestations, that result in chronic diarrhea,
abdominal distention, and failure to thrive.
 Causes of malabsorption
 Congenital
 Acquired
 Affect one or more of the different steps in the
intestinal hydrolysis and subsequent transport of
nutrients.
 The major site of absorption is the small intestine
 Carbohydrate, fat, or protein malabsorption is
caused by a disorder in the intestinal processes of
digestion, transport, or both of these nutrients
across the intestinal mucosa into the systemic
circulation.
 A congenital abnormality in the digestive or
absorptive processes or, more commonly, a

2. secondarily acquired disorder of such processes
may result in malabsorption.
Digestion and absorption
 Luminal phase:- dietary fats, proteins and
carbohydrates – solubilized by digestive enzymes
and bile – Deficiency in lipase and proteases leads
to lipid and protein malabsorption
 Mucosal phase:- brush-border hydrolase activity –
more common primary or secondary lactase
deficiency
 Postabsorptive phase:- hydrolyzed nutrients are
transported via lymphatic and portal circulation –
Impairs of chylomicrons and lipoproteins may
cause fat malabsorption or protein-losing
enteropathy Absorption of carbohydrates
 Of the carbohydrates most commonly present in
the diet (starches, sucrose, lactose), only starches
require preliminary luminal digestion by salivary
and, more importantly, pancreatic amylases.
 Despite the slow development of pancreatic
amylase, whose secretion reaches adult levels only
at 1 year of life, cooked starch malabsorption is
rare in infants because of the activity of the brush-
border glucoamylase that develops early in life.
Causes

3. Causes include the following:
 Carbohydrate malabsorption
 Starch molecules are primarily digested by
salivary and pancreatic amylase, but
glucoamylase in the intestinal brush boarder
also assists in digestion.
 Pancreatic insufficiency impedes the digestion
of large starch molecules.
 Absence or reduction of the brush border
disaccharidases causes selective carbohydrate
malabsorption.
 Transient reduction of these enzymes is
common after an infection in the intestine,
particularly a viral infection, because intestinal
villi and microvilli may be damaged.
 Glucoamylase and maltase are most resistant
to the depleting effects of mucosal injury that
result from infection, whereas lactase is the
most sensitive because of its predominant
distribution near the tips of the villi.
 Lack of sucrase and isomaltase is, by far, the
most frequent congenital enzyme deficiency.
This enzyme deficiency is inherited in an
autosomal recessive manner.

4.  Congenital lactase deficiency is exceedingly
rare, but adult-type lactase deficiency (also
called adult-type hypolactasia) is very common
in some ethnic groups.
 A congenital deficiency in the glucose
galactose transporter (SGLT-1) is inherited in
an autosomal recessive manner.
 Small bowel bacterial overgrowth of normal
flora alters the intraluminal metabolism of
carbohydrates and results in their
malabsorption. This entity should also be
suspected in children with diarrhea-
predominant irritable bowel syndrome.
 Bacteria ferment carbohydrates into smaller
osmotically active molecules and organic
acids. Increased osmolarity causes fluid from
systemic circulation to enter the intestinal
lumen, resulting in diarrhea.
 Organic acids stimulate motility and may
directly injure the intestinal mucosa.
Fermentation eliminates the reducing
substances and lowers the pH of the stool.

5.  The production of lactate and short-chain fatty
acids in the human colon can result in systemic
acidosis. In particular, a syndrome of D-lactic
acidosis may develop when specific bacteria
that are capable of producing this uncommon
and poorly cleared D isomer of lactate exist in
the intestinal flora.
 Bile acids are usually recycled by
enterohepatic circulation. Many factors can
prevent this recirculation. Bacterial overgrowth
of normal flora and growth of abnormal flora
are the most common causes of altered
intraluminal metabolism of bile acids.
 A congenital deficiency in the sodium–bile acid
cotransporter results in primary bile acid
malabsorption. The resulting diminished
transport of bile acids from the intestinal lumen
allows intestinal flora to deconjugate bile acids.
 Deconjugated bile acids directly inhibit the
carbohydrate transporters, reduce intraluminal
pH levels, and damage the enterocyte. They
may also directly stimulate the colon to secrete
fluid, contributing to diarrhea.
Fat malabsorption

6.  Increased delivery of fat to the colon results in
diarrhea and soft, pasty, foul-smelling stools.
However, the gas causes stools to float.
 Consequences include the malabsorption of fat-
soluble vitamins A, D, E, and K and insufficient
energy intake due to the high energy value of
dietary lipids.
 Exocrine pancreatic insufficiency is the principal
condition that results in severe fat
malabsorption. Pancreatitis, pancreatic cancer,
pancreatic resection, cystic fibrosis,
Shwachman-Diamond syndrome, Johnson-
Blizzard syndrome, and Pearson syndrome can
all result in pancreatic insufficiency.
 Significant obstructive biliary or cholestatic liver
disease or extensive intestinal mucosal
disease, such as occurs in celiac disease, may
also result in severe steatorrhea.
 Impaired bile production or secretion is seen in
liver or biliary tract disease. Inflammation or
resection of the ileum impedes enterohepatic
circulation, which results in a reduced bile acid
pool.
 Bacterial overgrowth in the small bowel
deconjugates bile acids, thereby inactivating
their ability to help lipids form a micelle. These

7. syndromes result in moderate lipid
malabsorption.
 Abetalipoproteinemia is a rare disorder with
autosomal recessive inheritance. Absence of
the lipoproteins results in cytoplasmic lipid
accumulation in the enterocyte. Lymphatic
transport of long-chain fats is impaired in
patients with abetalipoproteinemia,
lymphangiectasia, and protein-losing
enteropathy, resulting in moderate fat
malabsorption.
Protein malabsorption
 Protein malabsorption is a fairly common result
of exocrine pancreatic enzyme deficiency, as
occurs in patients with cystic fibrosis.
 Protein malabsorption that results from
congenital enterokinase deficiency is well-
described but rare.
 Creatorrhea, loss of protein in the stool (ie,
protein-losing enteropathy), is often caused by
the leakage of protein from the serum due to
inflammation of the mucosa, as in Crohn
disease, celiac disease, and protein sensitivity
syndromes.

8.  Congenital lymphangiectasia, a developmental
disorder in which dilation and dysfunction of
intestinal lymphatics occurs, often in association
with limb edema (Milroy disease), may present
with severe protein-losing enteropathy without
mucosal injury.
Vitamin malabsorption
 Malabsorption of vitamin B-12 and folate is
associated with tropical spruce, a disorder that
is acquired after travel to tropical areas.
 Vitamin B-12 is absorbed in the ileum, and
absorption requires an intrinsic factor made in
the gastric parietal cell. Intrinsic factor
deficiency that results from atrophic gastritis or
absence (from resection) or disease of the
terminal ileum (the predominant site of active B-
12) results in vitamin B-12 malabsorption.
Symptoms
 Diet history: Obtain a complete history of the
patient's diet, including the amount and type of
fluids, solid foods, and formula ingested. Caregivers
should keep a detailed journal of the patient's diet
and symptoms for a minimum of 1 week.
 The proper amount of fluid for most young
children is around 100 mL/kg/d. Fluid intake that
exceeds this amount may result in looser stools,

9. which causes a referral for a suspected but
nonexistent malabsorption.
 Fat is important for slowing the movement of
food through the intestine via hormonal
mechanisms. Fat intake of less than 3 g/kg/d
may contribute to toddler's diarrhea, especially
in the setting of excessive free fluid and
carbohydrate intake (eg, as occurs with large
amounts of fruit juice intake). Thus, history is
important in differentiating the common toddler's
diarrhea from the rarer malabsorption
syndromes.
 In the United States, juice is commonly
introduced into the diet in the latter portion of
the first year of life. Purple grape juice has a
high osmolarity, which can cause osmotic
diarrhea. The transport of fructose into
enterocytes is not active and relatively
inefficient. Apple and pear juice contain a high
fructose-to-glucose ratio, and consumption of
these juices can result in fructose
malabsorption and diarrhea. Because sorbitol
and fructose compete for the same intestinal
transporter, ingesting them together may result
in the malabsorption of these sugars.
 GI tract symptoms: GI tract symptoms are common
in patients with malabsorption syndromes, and
symptoms range from mild abdominal gaseous
distention to severe abdominal pain and vomiting.
Chronic or recurrent diarrhea is by far the most
common symptom.
 Abdominal distention and watery diarrhea, with
or without mild abdominal pain, associated with

10. skin irritation in the perianal area due to acidic
stools are characteristic of carbohydrate
malabsorption syndromes.
 Periodic nausea, abdominal distention and pain,
and diarrhea are common in patients with
chronic Giardia infections.
 Vomiting, with moderate-to-severe abdominal
pain and bloody stools, is characteristic of
protein sensitivity syndromes or other causes of
intestinal injury (eg, inflammatory bowel
disease).
 Recurrent abdominal pain has been implicated
as a symptom of dietary disorders, although
psychological variables that relate to an
elevated anxiety level have clouded the
certainty of this relationship. Malabsorption
syndromes can definitely cause abdominal pain
or irritability (particularly seen in celiac disease).
 Failure to identify the cause of malabsorption
can result in the misdiagnosis of a physiologic
syndrome as a behavioral disorder. Some
dietary items may cause symptoms only when
they are taken alone or with other specific
dietary items.
 Poor appetite is common in food sensitivity
syndromes. The child becomes conditioned to
refuse foods that cause inflammatory reactions
of the intestine. However, this is not typically
obvious in celiac disease. Malabsorption
syndromes not associated with inflammatory
reactions typically cause an increase in appetite
(eg, cystic fibrosis), unless the associated

11. abdominal gaseous distention hampers intake
and induces early satiety.
 Stool characteristics
 Patients with toddler's diarrhea often have loose
stools with undigested food particles. This
should not be taken to imply the presence of
true malabsorption.
 Frequent loose watery stools may indicate
carbohydrate intolerance.
 Pasty or loose foul-smelling stools indicate fat
malabsorption, also termed steatorrhea. This
symptom is commonly seen
in Giardiainfections, enterokinase deficiency,
hepatic and pancreatic dysfunction, and protein
sensitivity syndromes.
 Bloody stools are seen in patients with protein
sensitivity syndromes and not in disaccharidase
and pancreatic enzyme deficiencies or in
patients with giardiasis.
 Other symptoms
 Systemic symptoms, including weakness,
fatigue, and failure to thrive, are systemic
consequences of chronically poor nutrient
absorption. Malabsorption of carbohydrates,
fats, or proteins can cause failure to thrive,
whereas folate and B-12 malabsorption result in
macrocytic anemia.
 Patients with abetalipoproteinemia develop
retinitis pigmentosa and ataxia because of

12. chronic fat-soluble vitamin malabsorption and
deficiency (vitamins A and E).
Treatment
 When a child suffers from malnutrition, malabsorption is
just one of the possible causes. She might be
undernourished because she’s not getting enough of the
right types of food, or she has digestive problems that
prevent her body from digesting them. She also might
have a combination of these problems.
 Before prescribing a treatment, the pediatrician must
determine the cause. This can be done in one or more of
the following ways.
 The pediatrician may test the child’s ability to digest
and absorb specific nutrients. For example, the
doctor might have her drink a solution of milk sugar
(lactose) and then measure the level of hydrogen in
her breath afterward. This is known as a lactose
hydrogen breath test.
 The pediatrician may collect and analyze stool
samples. In healthy people, only a small amount of
the fat consumed each day is lost through the stool.
If too much is found in the stool, it is an indication of
malabsorption.
 Collection of sweat from the skin, called a sweat
test, may be performed to see if cystic fibrosis is
present. In this disease, the body produces
insufficient amounts of certain enzymes necessary

13. for proper digestion and an abnormality in the
sweat.
 In some cases the pediatrician might request that a
pediatric gastroenterologist obtain a biopsy from the
wall of the small intestine, and have it examined
under the microscope for signs of infection,
inflammation, or other injury.
Reference:-
 Kapitan Pediatrics Book
 GHAI Essential Pediatrics (Eighth Edition)
 Health line ( https://www.healthline.com )
 WebMd ( https://www.webmd.com )
 Mayo Clinic ( https://www.mayclinic.org )
 My Self