2. Definition
• Disorders of absorption constitute a
broad spectrum of conditions with
multiple etiologies and varied clinical
manifestations.
• almost all of these clinical problems are
associated with diminished intestinal
absorption of one or more dietary
nutrients.
3. Functions of intestinal epithelia
• nutrient digestion and absorption
• Barrier and immune defense
• Fluid and electrolyte absorption and
secretion
• Synthesis and secretion of several
proteins
• Production of several bioactive amines
and peptides
4. Bile Acids
• primary bile acids-synthesized in the liver
from cholesterol
- cholic acid and chenodeoxycholic acid
• secondary bile acids-synthesized from
primary bile acids in the intestine by
colonic bacterial enzymes
- deoxycholic acid and lithocholic acid
5. Functions of bile acids
(1)to promote bile flow,
(2) to solubilize cholesterol and
phospholipid in the gallbladder by
mixed micelle formation,
(3) to enhance dietary lipid digestion and
absorption by forming mixed micelles in
the proximal small intestine.
8. lipid digestion and absorption
• (1) a digestive phase-both lipolysis and micelle
formation requiring pancreatic lipase and
conjugated bile acids, respectively, in the
duodenum;
• (2) an absorptive phase for mucosal uptake
and reesterification;
• (3) a postabsorptive phase that includes
chylomicron formation and exit from the
intestinal epithelial cell via lymphatics.
9. Carbohydrates
• absorbed only in the small intestine in the
form of monosaccharides.
• starch and disaccharides -digested by
pancreatic amylase and intestinal brush
border disaccharidases to monosaccharides.
• Monosaccharide absorption occurs by a Na-
dependent process mediated by the brush
border transport protein SGLT1.
10. Proteins
• Present as polypeptides and requires
extensive hydrolysis to di- and tripeptides and
amino acids before absorption.
• Proteolysis –in stomach and small intestine
• mediated by pepsin secreted as pepsinogen
by gastric chief cells and trypsinogen and
other peptidases from pancreatic acinar cells.
11. Activation of proenzymes:
• pepsinogen to pepsin
-by pepsin in the presence of a pH <5
• Trypsinogen to trypsin
-by the intestinal brush border enzyme
enterokinase and subsequently by
trypsin
12. Classification and etiology:
Disorders of intraluminal digestion
• Pancreatic insufficiencies:
-cystic fibrosis
-chronic pancreatitis
-carcinoma of pancreas
• Bile salt insufficiency:
-obstructive jaundice
-bacterial overgrowth
13. • Enzyme inactivation
-Zollinger-Ellison Syndrome
• Rapid transit of food through gut
-Gastroenterostomy
-partial gastrectomy
• Increased bile salt loss in faeces
-terminal ileal disease- Crohn’s disease
-terminal ileal resection
• Lack of intrinsic factor
-pernicious anaemia
14. Disorders of transport in the intestinal
mucosal cell
• Defect in brush border hydrolysis
-lactase deficiency
• Defect in epithelial transport
-coeliac disease
-tropical sprue
-lymphoma
-Whipple’s disease
15. Disorders of transport from mucosal cell
• Lymphatic obstruction
-abdominal lymphoma
-tuberculosis
-lymphangiectasia
• Defect in epithelial processing
-abetalipoproteinaemia
17. Drugs causing malabsorption:
• Colchicine-inhibits crypt cell division and
lactase
• Neomycin-precipitation of bile salts in
gut,inhibition of lactase
• Methotrexate-folic acid antagonist
causing inhibition of crypt cell division
• Cholestyramine-binding bile salts
• Laxatives
18. Clinical features
• Diarrhoea, often steatorrhoea
-Steatorrhoea-an increase in stool fat
excretion of >6% of dietary fat intake
-loose,pale,bulky foul smelling stool
that float on water and difficult to
flush away
• bloating, flatulence and abdominal
discomfort.
19. • Weight loss
• Growth retardation, failure to thrive,
delayed puberty in children
• Swelling or edema
• Anaemias, presenting as fatigue and
weakness.
• Muscle cramp, osteomalacia and
osteoporosis
• Bleeding tendencies
20. Tests for steatorrhea
• Quantitative test
–72hr stool fat collection – gold standard
• > 6gm/day – pathologic
21. • Qualitative tests
–Sudan lll stain
• Detect clinically significant steatorrhea in
>90% of cases
–Acid steatocrit – a gravimetric assay
• Sensitivity – 100%, specificity – 95% , PPV
– 90%
–NIRA (near infra reflectance analysis)
• Equally accurate with 72hr stool fat test
• Allows simultaneous measurement of
fecal fat, nitrogen, CHO
22. Schilling test
• To determine the cause of cobalamine
(B12) malabsorption
• Helps to asses the integrity of gastric,
pancreatic and ileal functions.
• Abnormal cobalamine absorption in:
pernicious anemia, chronic
Pancreatitis, achlorhydria,bacterial
overgrowth, ileal dysfunction
23. • 58
Co-labeled cobalamin adminitered orally &
collect urine for 24 h,
• Urinary excretion of cobalamin will reflect
cobalamin absorption provided that
intrahepatic binding sites for cobalamin are
fully occupied.
• To ensure saturation of hepatic cobalamin
binding sites, 1 mg cobalamin is administered
intramuscularly 1 h following ingestion of the
radiolabeled cobalamin.
• <10% excretion in 24 h-abnormal
24. Urinary D-xylose test
• assessment of proximal small-intestinal
mucosal function
• a pentose,absorbed almost exclusively in the
proximal small intestine
• Give 25 g D-xylose and collecting urine for 5 h.
• abnormal test (<4.5 g excretion) primarily
reflects the presence of duodenal/jejunal
mucosal disease.
25. • Can also be abnormal in patients with blind
loop syndrome (as a consequence primarily of
abnormal intestinal mucosa)
• false-positive-patients with large collections of
fluid in a third space (i.e., ascites, pleural
fluid).
26. • Tests for pancreatic insufficiency
–Stimulation of pancreas through
administration of a meal
or hormonal secretagogues , then
analysis of duodenal
fluid
–Indirect tests – schilling test
• Tests for protein malabsorption
Enteral protein loss measuring
alpha-1 antitirypsin clearance
27. Endoscopy
• Gross morphology – gives diagnostic clue
–Cobblestone appearance – Crohn’s
disease.
–Reduced duodenal folds and scalloping
of duodenal mucosa – celiac disease
•Use of vital dyes to identify villous
atrophy
28. Biopsy of Small-Intestinal Mucosa
• primary indications
(1) evaluation of a patient either with
documented or suspected steatorrhea or with
chronic diarrhea
(2) diffuse or focal abnormalities of the small
intestine defined on a small-intestinal series
29. • Lesions seen – classified into three
1. Diffuse,specific
– Whipple’s disease,
– Agammaglobulinemia,
– Abetalipoproteinemia
2. Patchy, specific
– Crohn’s disease,
– Intestinal lymphoma
• Suspected distal pathology - push
enteroscopy
wireless capsule endoscopy
31. Barium studies
• evaluation of the patient with presumed or
suspected malabsorption
• small-bowel series -a useful examination to
look for anatomical abnormalities, such as
strictures and fistulas (as in Crohn's disease)
or blind loop syndrome (e.g., multiple jejunal
diverticula), and to define the extent of a
previous surgical resection
32. Treatment
• Replacement of nutrients, electrolytes and
fluid may be necessary.
• In severe deficiency, hospital admission may
be required for parenteral administration.
• Pancreatic enzymes are supplemented orally
in pancreatic insufficiency.
33. • Dietary modification is important in some
conditions:
–Gluten-free diet in coeliac disease.
–Lactose avoidance in lactose intolerance.
• Antibiotic therapy will treat Small Bowel
Bacterial overgrowth.
34. CELIAC SPRUE
• Etiology
–Hypersensitivity to Gliadin portion of
gluten (wheat, barley, rye)
–IgA antigliadin, IgA antiendomysial,
and IgA anti-tTG antibodies
• Familial clustering
–HLA-B8, DQw2 on Chromosome 6
• Classic flat mucosal lesion
35. Tropical Sprue
• manifested by chronic diarrhea, steatorrhea,
weight loss, and nutritional deficiencies,
including those of both folate and cobalamin
• affects 5–10% of the population in some
tropical areas
• etiology and pathogenesis of tropical sprue
are uncertain
• Klebsiella pneumoniae, Enterobacter cloacae,
or E. coli
36. Short Bowel Syndrome
• clinical problems that occur following
resection of varying lengths of small intestine
• any age from neonates through the elderly.
• Following resection, the residual intestine
undergoes adaptation of both structure and
function that may last for up to 6–12 months.
37. • Continued intake of dietary nutrients and
calories is required to stimulate adaptation
• . Thus, enteral nutrition and calorie
administration must be maintained
38. Bacterial Overgrowth Syndrome
• a group of disorders with diarrhea,
steatorrhea, and macrocytic anemia whose
common feature is the proliferation of
colonic-type bacteria within the small
intestine
• due to stasis caused by
• impaired peristalsis (functional stasis),changes
in intestinal anatomy (anatomic stasis), direct
communication between the small and large
intestine
39. Whipple's Disease
• a chronic multisystem disease associated with
diarrhea, steatorrhea, weight loss, arthralgia,
and central nervous system (CNS) and cardiac
problems
• caused by the bacteria Tropheryma whipplei.
