Malabsorption Flashcards
Two substances preferentially absorbed by the distal small intestine?
Bile salts and B12
Two phases of intestinal absorption?
- Luminal - Alteration of physicochemical state of nutrients, so that they can be taken up by absorptive cells
- Intestinal - Processes occurring in cells and transport chennels of the intestinal wall
What processes occur in the luminal phase of digestion?
Pancreatic enzyme degradation and bile acid complexation
What determines bile quantity and quality?
- Adequate liver function
- Unobstructed bile flow
- Intact enterohepatic bile salt circulation
What is a frequent cause of luminal phase malabsorption?
Insufficient bile acids
Causes of luminal malabsorption?
- Iterruption of the normal continuity of the ddistal stomach and duodenum
- Pancreatic dysfn
- Deficient/ineffective bile salts due to: Impaired excretion of the bile, bacterial overgrowth, deficient bile salts
What does intestinal-phase malabsorption frequently reflect?
Specific enzyme defects
What do defects in microvilli often result in?
Malabsorption of sugars (ie primary disaccharidase deficiencies)
What is short bowel syndrome?
Malabsorption due to resection of the small bowel
A disorder in which absorptive cells cannot synthesize the apoprotein required for the assembly of lipproteins and chylomicrons?
Abetalipoproteinemia
Lactose tolerance test?
Measuring blood sugar after ingestion of a standard amount of disaccharide
Isotopically labeled vit B12 given orally and its blood level then determined?
Schilling test
Typical deficiency seen in generalized malabsorption?
Typically always impaired absorption of dietary fat
Describe the D-xylose absorption test
D-xylose does not require any component of the intestinal phase to be absorbed, so this test is used to evaluate the luminal phase of absorption
Utility of the 14CO2-cholyl-glycine breath test?
Measured in exhaled air after oral admin is a test of bile salt abs in the ileum
What causes intolerance to milk products?
Lactase deficiency
Characteristics of Celiac Disease?
- Generalized malabsorption
- Small intestinal mucosal lesions
- Prompt clinical and histopathological response to withdrawal of gluten-containing foods from diet
Crucial risk factors for celiacs?
- Genetic predisposition
- Gliandin
What are the compoents of grains that exacerbate celiac disease?
Gluten and gliandin
Relationship of adenovirus to celiac disease manifestation?
Adenovirus codes an AA that has homology to alpha-gliadin.
Histocompatibility complexes associated with celiac disease?
HLAB8, DR8, DQ2
What skin disease is associated with celiac disease?
Celiac herpetiformis
What are the characterisitcs of fully developed celiac disease?
- Blunting/total disappearance of villi
- Damaged mucosal surface epithelial cells with numerous intraepithelial lymphocytes
- Increased plasma cells in the lamina propria but not in the deep layers
Number one characteristic of celiac disease?
Generalized malabsorption
Tests used to ID celiac disease?
- IgA antiendomysial Ab
- antitissue transglutaminase Ab
Number one Tx to lead to complete and prolonged clinical/histopathologic remission?
- Strict gluten free diet
Probable cause of refractory sprue?
Monoclonal T-cell proliferation
Syndrome that autoimmune enteropathy is found?
IPEX syndrome
- X-linked
- Immunodysregulation
- Polyendocrinopathy
- enteropathy
Due to FoxP3 mutation
What is Whipple disease?
Small bowel filled with macrophages packed with small rod-shaped bacteria
Bug that causes Whipple Disease?
Tropheryma whippelii
Probable pathogenesis of Whipple Disease?
Impaired ability to degrade intracellular microorganisms; Circulating cells expressing CD11b are reduced. CD11b is used to activate macrophages.
What does abetalipoproteinemia involve?
Failure to make apoprotein B
What is apoprotein B typically used for?
Chylomicrons do not assemble and lipids cannot be transported out of cells
What does abetalipoproteinemia lead to?
Acanthocytosis in erythrocytes and selective demyelinization
Absorption of what vitamins are impaired in abetalipoproteinemia?
ADEK
Lymphangiectasia and peripheral lymphedema?
Milroy disease
What is lymphangiectasia?
Pathologic dilation of lymph vessels
Cause of tropical sprue?
Etiology unknown, some studies suggest long-term contamination of the bowel with bacteria
What does tropical sprue cause?
Folate deficiency
