Tests for malabsorption

1. TESTS FOR MALABSORPTION
• CHAIR PERSON: DR KALINGA .B.E
• STUDENT: DR SHRIDEVI

2. INTRODUCTION
• Maldigestion: Defective intraluminal hydrolysis of nutrients. There is
impaired breakdown of nutrients (carbohydrates, protein, fat) to
absorbable split-products (mono-, di-, or oligosaccharides;
aminoacids; oligopeptides; fatty acids; monoglycerides)
• Malabsorption: Defective mucosal uptake and transport of
adequately digested nutrients including vitamins and trace elements

3. The integrated processes of digestion and absorption can be
described in three phases:
• Luminal Phase
• Mucosal phase
• Postabsorbtive /Removal phase
Disturbances of the absorptive process can take place in any of these
three phases or defect in one or more than one can coexist

4. Normal physiology
3 major phases: –
• Luminal phase :dietary fats, proteins, and carbohydrates are
hydrolyzed and solubilized depending largely on pancreatic and biliary
secretions.
• Mucosal phase :During the mucosal phase final hydrolysis and uptake
of saccharides and peptides takes place from lumen into cells and
lipids taken up by epithelial cells are processed and packaged for
cellular export.
• Post-absorptive phase: transported via lymphatics and portal
circulation from epithelial cells to other parts of the body.

5. Defects in luminal phase

6. Defects in mucosal phase

7. Defects in post absorptive processing phase
• Enterocyte processing : Abetalipoproteinemia
• Lymphatic : intestinal lymphangiectasia

8. Useful lab tests for patients with suspected malabsorpton and for
establishing possible nutrient deficiency

10. TESTS FOR FAT MALABSORPTION
 QUANTITATIVE FECAL FAT ANALYSIS:
The van de Kamer method:
• This method converts the lipids in the stool to fatty acids
• Then by using sodium hydroxide the specimen is titrated until neutral end
point.
• gold standard for fecal fat analysis.
• Fecal fat excretion of less than 7 g/day with a fat intake of 100 g/day
usually is considered normal.
• With significant diarrhea, a fecal fat excretion of 14 g/ day should be used
as the upper limit of normal

11. Limitations are:
(1) If the main symptom of malabsorption is chronic diarrhea,
measurement of fecal fat might not influence the subsequent
evaluation, because the diagnostic tests performed to establish the
etiology of diarrhea are similar to the tests for the workup of
steatorrhea.
(2) An elevated fecal fat level usually cannot differentiate among
biliary, pancreatic, and enteric causes of malabsorption

12. (3) In many patients with severe steatorrhea, the stools have a very foul
smell and a characteristic porridgelike appearance, and quantitative
studies are not necessary to establish fat malabsorption.
(4) Fat absorption may be normal despite malabsorption of other
nutrients, so a normal fat balance does not imply normal absorptive
function of the GI tract.
(5) Finally, accuracy depends on quantitative stool collections for 48 to
72 hours, adherence to a diet that contains 80 to 100 g of fat daily, and
a diet diary to determine fat intake

13. Acid steatocrit (AS) test:
 Semiquntitative fecal fat test.
 A sample of stool is diluted 1 : 3 with distilled water in a test tube.
 The diluted stool is homogenized, and a 500-µL aliquot is pipetted
into a tube.
 Then 100 mL of 5M HClO4 is added to allow better fat extraction and
separation of the lipid layer.
 An aliquot of the diluted stool-HClO4 mixture is put into a non-
heparinized microcapillary tube and sealed on one end.

14. • After centrifugation of this aliquot at 13,000 rpm for 15 minutes, the
fatty layer (FL) and the solid layer (SL) are measured, and the AS is
determined according to the following equation:
An AS of less than 31% is normal.

15.  SUDAN III STAIN
• Qualitative Fecal Fat Analysis.
• A sample of stool is placed on a glass slide to which several drops of
glacial acetic acid and Sudan III stain are added.
• The slide is held over a flame-burner, and the acidified mixture is
heated to boiling then examined while still warm for the presence of
orange fat globules.
• A count of up to 100 globules, each with a diameter less than 4 mm,
per high-power field is normal.

16. Breath Tests for Fat Malabsorption:
• The principle of the 14C-triolein breath test is to measure 14CO2 in
the breath after ingestion of a triglyceride that has been radiolabeled
with 14C.
• Fat malabsorption results in decreased pulmonary excretion of 14CO

17. Serum Tests for Fat Malabsorption:
• The photometric measurement of β-carotene at 456 nm has been
suggested as a useful screening test for steatorrhea .
• Values less than 100 mg per 100 mL suggest the presence of
steatorrhea.
• Values less than 47 mg per 100 mL strongly indicate steatorrhea.
• Concentrations in excess of 100 mg per 100 mL do not exclude mild
steatorrhea, although they make steatorrhea with fat losses in excess
of 16 g/day very unlikely.

18. TESTS FOR BILE SALT MALABSORPTION
Measurement of Fecal Bile Acid Output:
• Measurement can be performed by enzymatic methods or by gas
chromatography.
• This test requires a quantitative stool collection, and the analytic
techniques are time consuming and require considerable expertise.
• Enzymatic methods may be unreliable in severe steatorrhea

19. 14Carbon-Taurocholate Bile Acid Absorption Test :
• The 14C-taurocholate bile acid absorption test requires a 72-hour
stool collection after ingestion of radioactively labeled bile acid.
• The rate of intestinal bile acid absorption is calculated from the fecal
recovery of 14C-labeled taurocholic acid (14C-TCA).

20. Therapeutic Trial of Bile Acid-Binding Resins (Cholestyramine) :
• A therapeutic trial of cholestyramine or other bile acid- binding resins
can be used to diagnose bile acid malabsorption as a cause of
diarrhea.
• Failure of diarrhea to remit within 3 days of initiation of
cholestyramine makes bile acid malabsorption an unlikely cause of
diarrhea.

21. Selenium-75-Labeled Homotaurocholic Acid Test (SeHCAT) :
• The radioactive taurocholic acid analog used for this test is resistant
to bacterial deconjugation.
• After it has been administered orally, the patient undergoes serial
gamma scintigraphy to measure whole-body bile acid retention.

22. TESTS FOR CARBOHYDRATE MALABSORPTION
As a general rule, tests for carbohydrate malabsorption rely upon the fermentation
of undigested carbohydrates
 D-xylose test
• Measures the absorptive capacity of the proximal small intestine
• Pentose monosaccharide
• Active sodium transporter and by passive diffusion
• Measure of the permeability of the proximal small intestine, rather than a
specific defect in D-xylose absorption
• Overnight fast
• Ingests a 25 g dose of D-xylose
• Urine is collected for the next five hours
• Normal excretion of D-xylose is 6.0 +/- 1.5 g
• Serum D-xylose concentration less than 20 mg/dL suggests abnormal absorption

23.  Lactose tolerance test
• Oral administration of a 50 g test dose
• Blood glucose levels are monitored at 0, 60, and 120 minutes
• Increase in blood glucose by <20 mg/dL + the development of
symptoms is Diagnostic
 Measurement of breath hydrogen following lactose
challenge
• Increase in breath hydrogen by more than 20 ppm is diagnostic.

24. Tests for bacterial overgrowth
• Direct quantitative measurement of bacterial counts from aspirated
intestinal fluid.
• Normal counts < 104/ml in the jejunum and 105 /ml in the ileum
• Hydrogen breath tests with lactulose

25. TEST FOR VITAMIN B12 MALABSORPTION
Schilling test
• Identifies the cause of vitamin B12 malabsorption
• Rarely performed

27. Stage 1
 Administer a small oral dose 1ug of radiolabeled vitamin B12
• within one or two hours, a large intramuscular flushing dose of
nonradiolabeled vitamin B12
Unlabeled B12 saturates vitamin B12 carriers
• radioactive vitamin B12 absorbed by the intestine is excreted in the
urine
 If less than 7% to 10% of the administered dose is recovered in urine
within 24 hours
• vitamin B12 malabsorption is confirmed

28. Stage 2
 oral administration of intrinsic factor done.
• pernicious anemia
• normalize after oral administration of intrinsic factor
Stage 3- In small bowel bacterial overgrowth(SIBO)
• improve after antibiotic therapy
Stage 4-Patients with pancreatic exocrine insufficiency
• normalize with addition of pancreatic enzymes

29. TESTS FOR PANCREATIC EXOCRINE
INSUFFICIENCY INSUFFICIENCY
Direct tests
• administration of a meal or hormonal secretagogues
• stimulation of the pancreas
• duodenal fluid is collected and analyzed
• quantify normal pancreatic secretory content (ie, enzymes, and
bicarbonate).
• A normal person should release a large volume of bicarbonate-rich
pancreatic fluid in response to the intravenous injection of secretin.
Indirect tests :measure the consequences of pancreatic insufficiency and
are more widely available
• insensitive to early pancreatic insufficiency

32. Serology :
Serum anti-TTG, Serum antigliadin ,antiendomysial antibodies
- many pts with biopsy confirmed celiac have negative IgA
antibodies screen due to concurrent selective IgA deficiency which is
common in celiac disease
-If IgA serology is negative and suspicion is high
 Serum IgA -IgA deficiency.

33. Intestinal Permeability Tests:
• Intestinal permeability tests mostly are used in studies of the
pathophysiology of intestinal disorders.
• Most current permeability tests are based on the differential
absorption of mono- and disaccharides.
• Damage to the mucosa can result in increased permeability for
disaccharides and oligosaccharides consequent to epithelial injury,
and this can result in decreased permeability of monosaccharides
secondary to reduction of mucosal surface area.
• Absorption is measured by urinary excretion.
• Results are expressed as the absorption ratio of the mono- and
disaccharides.

34. Ultrasonography
To look for:
• Small bowel thickening to rule out inflammatory disease of small
intestine like chrohs disease, whipples disease, celiac disease
• Pancrease to rule out pancreatic tumour , calcification, dilatation of
pancreatic duct or stone in pancreatic duct
• Lymphadenopathy , ascites
• Hepatobiliary system

36. Plain abdominal x-ray film:
• Pancreatic calcifications are indicative of chronic pancreatitis

38. Small bowel barium studies:
• mucosa pattern associated with celiac disease
 obliterated or coarsened.
• Small bowel dilatation and diverticulosis
 scleroderma
• Regional enteritis of the small intestine
 Stricture
 Ulceration
fistula formation
• Other anatomic abnormalities, such as surgical changes or enterocolonic
fistula

39. Film from a barium follow-through study of
the small bowel in a patient with tropical
sprue showing loss of the normal feathery
mucosal pattern in the small bowel, with
dilatation of jejunal loops and thickening of
the mucosal folds.

40. Intestinal TB

41. BARIUM STUDY IN ULCERATIVE COLITIS PATIENT

42. CT scan of the abdomen:
• evidence of chronic pancreatitis, such as pancreatic calcification or
atrophy
• Enlarged lymph nodes
• Whipple disease
• lymphoma

43. Endoscopic retrograde cholangiopancreatogram
(ERCP): – pancreatic or biliary-related disorders

44. Film from an ERCP
demonstrating subtle
changes limited to the side
branches (arrows) in a
patient in whom a direct
pancreatic function (secretin)
test indicated chronic
pancreatitis

45. EUS of the pancreatic body in a patient
with chronic pancreatitis.

46. UPPER GI ENDOSCOPY WITH SMALL BOWEL
MUCOSAL BIOPSY
Examples of conditions that can be diagnosed this way include
• celiac sprue,
• giardiasis,
• Crohn disease,
• Whipple disease,
• amyloidosis,
• abetalipoproteinemia,
• and lymphoma

47. Endoscopic view
of the duodenum
showing
scalloping of the
folds in a patient
with celiac
disease

48. Endoscopic view of the second
part of the duodenum in a
patient with tropical sprue
showing scalloping of the
duodenal mucosa, a finding due
to villus atrophy

49. INTESTINAL LYMPHANGIECTASIA
SHOWING WHITISH STUDDED
APPEARANCE

50. DUODENAL DIVERCULUM

51. CHROHNS DISEASE

52. BIOPSY

54. Duodenal biopsy specimen of patient with
untreated celiac disease

55. Duodenal biopsy specimen from a patient with Whipple’s disease. A, H&E staining shows villus blunting. Lamina propria is
infiltrated with pale-staining foamy macrophages.
B, High-power view demonstrates purple-red macrophages. (Periodic acid–Schiff stain.)

57. Duodenal biopsy of
patient with non
granulomatous
chronic idiopathic
enterocolitis

58. NORMAL SMALL BOWEL MUCOSA CELIAC DISEASE

59. ASPIRATION
• Fluid aspirated- Descending part of duodenum/jejunum.
• Examined microscopically for Giardia
• Cultured to detect SIBO-
 Gold standard for diagnosis.
 Normal counts rarely exceed 104 /mL in the jejunum and 105
/mL in the ileum.

60. VIDEO CAPSULE ENDOSCOPY
 For capsule endoscopy, the patient swallows a disposable capsule
that contains a complementary metal oxide silicon (CMOS) chip
camera.
 Color still images are transmitted wirelessly to an external receiver
at several frames per second until the capsule’s battery is exhausted
or it is passed into the toilet.
 Capsule endoscopy enables visualization of the small-bowel mucosa
beyond the reach of a conventional endoscope and, at present, is
solely a diagnostic procedure.
• Used to diagnose a wider range of disease such as crohn’s , celiac
disease and other malabsorptive disease.
• In refractory celiac disease, VCE can detect changes such as
ulcerations and strictures that suggest T- cell lymphoma

61. Balloon Enteroscopy
• In some case of malabsorption, balloon enteroscopy with biopsies of
the jejunum and ileum can be helpful to establish the diagnosis.
• Comparison of VCE and BE
 Advantage-biopsy from altered mucosa area
 Disadvantage- time consuming and uncomfortable for the patients

62. REFERENCES
• SLEISENGER AND FORDTRANS GASTROINTESTINAL AND LIVER
DISEASE 10th edition
• HARRISON 20th edition

63. Thank You