2. DEFINITION
The term malabsorption denotes disorders in which
there is a disruption of digestion and nutrients
absorption.
Impairment can be of single or multiple depending on
the abnormality.
This may lead to malnutrition and a variety of
anaemias.
3. PATHOPHYSIOLOGY :
Digestion is by enzymatic hydrolysis which is initiated by
intraluminal processes requiring gastric,pancreatic, and
biliary secretions.
The final products of digestion are absorbed through the
intestinal epithelial cells.
Malabsorption constitutes the pathological interference with
the normal physiological sequence of digestion (intraluminal
process), absorption (mucosal process) and transport
(postmucosal events) of nutrients.
6. CLINICAL FEATURES
Diarrheoa, often steatorrhoea is the most common feature.
Watery,diurnal and nocturnal,bulky,frequent stools are the
clinical hallmark of overt malabsorption.
It is due to impaired water, electrolyte absorption or
irritation from unabsorbed fatty acid.
Bloating, flatulence and abdominal discomfort also seen.
Cramping pain suggests obstructive intestinal segment
especially if it persist after defecation. Eg; Crohn’s disease.
7. Weight loss can be significant despite increased oral intake
of nutrients.
Growth retardation,failure to thrive,delayed puberty are seen
in children.
Swelling or oedema are seen due to loss of protein.
Anaemias, commonly from vitamin B12, folic acid and iron
deficiency presenting as fatigue and weakness.
Muscle cramp from decreased vitamin D, calcium absorption
and they lead to osteomalacia and osteoporosis.
Bleeding tendencies are seen from vitamin K and other
coagulation factor deficiencies.
8. DIAGNOSIS:
As a baseline,the estimation of full blood
count,ESR,haematinics in the form of folate,B12and
iron status and serum albumin with serum
calcium,phosphate and magnesium have to be done.
TESTS FOR FAT MALABSORPTION:
The following methods are available .
1.TOTAL FECAL FAT ESTIMATION:
Before the test, the patient is put on a high fat
diet, consuming between 50-150 g/day of fat for three
days.
The patient must collect their feces over the next 72
hours using a 1-gallon paint that can be well sealed.
9. The fecal sample must be refrigerated to prevent any
bacterial action.
Fecal fat analysis is performed by first weighing the sample
and then extracting the lipids with an organic solvent.
The extraction solvent is evaporated and the dry weight of
the fat that remains is measured.
Normal absorption of fat is indicated by a fecal fat level of
less than or equal to 7 grams per day.
2.FAT SCREENING:
A more simple but less accurate way to measure fat
absorption is to count the fat droplets in a well mixed
sample of the stool specimen using a microscope and a
neutral fat stain.
10. Another simplified screening test is the fat tolerance
test called the butterfat or the fatty meal test.
In this test,the patient is asked to fast overnight and is
given 1 gram of fat per kg of body weight.
Blood is drawn before the dose and again three and six
hours afterwards.
The fasting, three-hour and six-hour plasma samples
are analyzed for triglyceride concentration.
Normal absorption is indicated by at least a 50%
increase in triglycerides over the fasting level.
The 14C-triolein breath test can be useful to
make a diagnosis of steatorrhoea in patients
with difficult diarrhoea.
It has also been used to monitor pancreatic fat
malabsorption
11. TESTS FOR PANCREATIC MALABSORPTION
Non-invasive pancreatic function tests include
1.The pancreolauryl tests:
It requires the avoidance of Vitamin B and some drugs, and
two consecutive day 10 hour urine collections.
2.The PABA test:
It should be reported as a urinary PABA excretion index by
coadministration of p-aminosalicyclic acid or 14C-PABA.
Both these tests were acceptable as screening tests for
pancreatic exocrine insufficiency.
The invasive tests like secretin-cholecystokinin test and the
Lundh test are in research.
12. DISACCHARIDASE MALABSORPTION
The measurement of disaccharidases, usually
lactase, maltase and sucrase, is of limited use because
of high coefficients of Variation.
They have a role in diagnosing lactase deficiency and
limited use for monitoring disaccharidase deficiencies
in coeliac disease.
13. HYDROGEN BREATH TEST
The hydrogen breath test is used to measure two
things, carbohydrate malabsorption such as lactose
intolerance and bacterial overgrowth.
Hydrogen is produced by bacterial fermentation of
unabsorbed carbohydrates in the intestines.
The hydrogen produced goes into the blood stream and is
excreted through the lungs.
The test is done using a gas chromatograph, an apparatus
that can separate compounds from one another based on
their chemical composition.
14. The patient is asked to fast overnight, and his or her
breath is collected in a plastic syringe at the start of the
test.
The patient is then given something to eat depending
on what is being evaluated.
The patient's breath will be collected in a plastic
syringe every thirty minutes for the next two to five
hours, depending on the test.
The syringe will be capped and sent to the laboratory
for analysis.
The test is simple, non-invasive and not diagnostic, it
gives the doctor an idea of what may be wrong.
15. PROTEIN LOOSING ENTEROPATHY
Chromium radiolabelled albumin or alpha-1 antitrypsin
excretion are the definitive tests.
BILE ACID MALABSORPTION:
The SeHCAT test with a seven day retention is useful but, if
unavailable, a simple assessment of the clinical response of
diarrhoea to cholestyramine 4-8gms t.d.s. can be used.
16. TESTS FOR CELIAC DISEASE
Tests for this disease involve drawing the patient's blood and
testing for the presence of three
antibodies, antigliadin, antiendomysium, and antireticulin
antibodies.
17. D-XYLOSE ABSORPTION TEST
D-xylose is a pentose sugar that is not normally found in the
blood.
It can be easily absorbed by healthy intestinal cells without
the aid of pancreatic enzymes, and is poorly metabolized so
that at least 50% of the dose is excreted in the urine within 24
hours.
This test is a good general screen for malfunction of
absorption, and helps to differentiate intestinal
malabsorption syndromes (reduced Dxylose absorption)
from pancreatitis (normal D-xylose absorption).
18. Adults are given an oral dose usually 25 grams of D-
xylose.
A five-hour timed urine sample is collected, and a
blood sample is collected two hours after the dose is
given.
Children are given a 5 gram dose of Dxylose, and a
blood sample is collected one hour after the dose is
given.
19. Adults should excrete at least 25% of the dose in the
five-hour urine sample, and have a two-hour blood
level of at least 25 mg/dL.
Children should have a one-hour blood level of at least
20 mg/dL.
The D-xylose test will be normal if the patient has
normal absorptive capacity in the intestine, or if the
patient has malabsorption that is caused by a
pancreatic problem.
It will be low if the patient has celiac disease, tropical
sprue, Crohn's disease, advanced AIDs, or pellegra
(niacin deficiency).
20. TESTS FOR VITAMIN B12 DEFICIENCY
It is measured by Schilling test.it has 4 stages.
Stage 1: oral vitamin B12 plus intramuscular
vitamin B12
In the first part of the test, the patient is
given radiolabeled vitamin B12 to drink or eat.
An intramuscular injection of unlabeled vitamin B12 is
given at or around the same time.
.
21. The purpose of the single injection is to temporarily saturate
B12 receptors in the liver with enough normal vitamin B12 to
prevent radioactive vitamin B12 binding in body tissues
(especially in the liver), so that if absorbed from the G.I.
tract, it will pass into the urine.
The patient's urine is then collected over the next 24 hours to
assess the absorption.
In patients with pernicious anemia or with deficiency due to
impaired absorption, less than 5% of the radiolabeled
vitamin B12 is detected.
22. Stage 2: vitamin B12 and intrinsic factor
If an abnormality is found, the test is repeated, this
time with additional oral intrinsic factor.
If this second urine collection is normal, this shows a
lack of intrinsic factor production, or pernicious
anemia.
Stage 3: vitamin B12 and antibiotics
This stage is useful for identifying patients with
bacterial overgrowth syndrome.
Stage 4: vitamin B12 and pancreatic enzymes
This stage, in which pancreatic enzymes are
administered, can be useful in identifying patients
with pancreatitis.
23. BIOPSY OF SMALL INTESTINAL MUCOSA:
It is useful to confirm the diagnosis.
24.
25.
26. MALABSORPTION TREATMENT
Management includes
(1) the correction of nutritional deficiencies, and
(2) when possible, the treatment of causative diseases.
Nutritional support
Supplementing various minerals, such as
calcium, magnesium, iron, and vitamins, which may be deficient in
malabsorption, is important.
Caloric and protein replacement also is essential.
Medium-chain triglycerides can be used as fat substitutes because
they do not require micelle formation for absorption and their route
of transport is portal rather than lymphatic.
In severe intestinal disease, such as massive resection and extensive
regional enteritis, parenteral nutrition may become necessary.
27. Treatment of causative diseases
A gluten-free diet helps treat celiac disease.
Similarly, a lactose-free diet helps correct lactose intolerance;
supplementing the first bite of milk-containing food products
with Lactaid also helps.
Protease and lipase supplements are the therapy for pancreatic
insufficiency.
Antibiotics are the therapy for bacterial overgrowth.
Corticosteroids, anti-inflammatory agents, such as
mesalamine, and other therapies are used to treat regional
enteritis.
