Malabsorption Syndromes Flashcards
What are the two genotypes associated with celiac disease?
HLA-DQw2 & HLA-DQ8
What is an extra-intestinal manifestation of celiac disease?
- dermatitis herpetiformis
What is the definition of malabsorption?
A condition in which the normal digestion, absorption, or transport of various nutrients and minerals are interrupted, resulting in malnutrition, diarrhea, steatorrhea, and weight loss.
Define assimilation.
The process by which ingested food reach body fluid/cells.
Define Malnutrition
imbalance between supply of nutrients/energy and the body’s requirements
Define Maldigestion
impaired nutrient hydrolysis
What are the three main phases of nutrient absorption
- Luminal phase
- Mucosal phase
- Transport phase
What makes intrinsic factor?
Gastric parietal cells
Why is intrinsic factor important?
Important for B12 Absorption
What happens in the luminal phase?
Nutrients are hydrolyzed/solubilized in preparation for absorption
What are 3 abnormalities of the luminal phase?
- Reduced nutrient availability
- Impaired fat solubilization
- Defective nutrient hydrolysis
What is necessary for fat solubilization?
bile salts (form the micelles)
What are the presenting symptoms of impaired fat solubilization?
Steatorrea and Vit A,D,E,K deficiency
What happens in the mucosal phase of absorption?
Terminal hydrolysis of carbs & peptides
Fats are processed and packaged for export
What are 2 abnormalities of the mucosal phase?
- Diffuse mucosal disease or losss
2. Enterocyte defects
What do brush border membrane hydrolases do?
Break down carbs (oligosaccharides to monosaccharides
What happens with brush border hydrolase deficiency?
Carbs cannot be absorbed in the small intestine.
Carbs get metabolized by bacteria in the large intestine
—> results in gaseous distention & diarrhea
Name some brush border enzymes
Lactase Peptidase Glycoamylase Maltase Sucrase Nucleotidase Enterokinase Phosphatase
What is the most common brush border membrane hydrolysis deficiency?
What are the effects of this deficiency?
Lactase
Results in milk intolerance (diarrhea, …)
What tests would be used to assess malabsorption?
- CBC, ESR, INR
- Fe, folate, & B12 levels
- albumin, prealbumin, transferrin
- Ca, PO4, Mg
- Fat malabsorption: fecal fat excretion, Sudan III stain, 14C-Triolein breath test
What is the Sudan III stain?
What is its purpose?
A quantitative examination of the stool for undigested muscle fibers, neutral and split fats.
It screens for steatorrhea
What is the 14C-Triolein breath test?
A test that measures radiolabelled 14C in CO2 that gets exhaled. This CO2 was produced from hydrolysis of the tryglyceride, Triolein.
What main symptom will a pt with carbohydrate malabsorption present with? Describe the mechanism for this.
Watery diarrhea
Carbs are not absorbed in small intestine, carbs reach large intestine and are metabolized by gut bacteria into short-chain fatty acids –> increase in osmotic load.
Name two tests for carbohydrate malabsorption.
D-Xylose test
Lactose/Hydrogen breath test
How is exhaled Hydrogen produced?
Only by bacterial metabolism of carbs.
What is the D-xylose test?
A test that measures maximal intestinal absorption area.
Xylose is absorbed in duodenum and jejunum.
Test measures blood [D-xylose] 2 hrs after ingestion.
What is an ERCP test?
Endoscopic Retrograde Cholangiopancreatogram
- looks at pancreatic duct for obstruction (stone, tumuor, mass, pancreatitis)
- will also assess biliary tree for presence of strictures or psuedocyst
What does a biopsy (histology) of Celiac disease look like?
Loss of villi on top of intestinal epithelium - lumenal side appears flat
What is terminal ileitis?
Inflammation of the terminal colon
If a patient is found to have terminal ileitis, what is the most likely diagnosis?
Crohn’s disease
