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MALABSORPTION

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Title: MALABSORPTION


1
MALABSORPTION
  • M.Prasad Naidu
  • MSc Medical Biochemistry,
  • Ph.D.Research Scholar

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.

4
  • CLASSIFICATION

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  • 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 Crohns 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.

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  • 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
  • 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.

24
BIOPSY OF SMALL INTESTINAL MUCOSA
  • It is useful to confirm the diagnosis.

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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.

28
  • 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.

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