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MS2 GI > 10/15- Malabsorption > Flashcards

10/15- Malabsorption Flashcards

(53 cards)

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1
Q

Effects of Billroth II (gastric surgery)?

A
  • Loss of antrum -> poor grinding
  • Loss of pylorus
  • Asynchronous bile and pancreatic secretions
  • Poor mixing
  • Blind loop
  • Abnormal motility and poor mixing
  • Gastrojejunostomy
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2
Q

What are the different classes of nutrients?

A
  • Fats
  • Carbohydrates
  • Proteins
  • Vitamins
  • Minerals
  • Water
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3
Q

What is the most energy dense nutrient?

A

Fat

  • 9 kcal/g
  • Intake 60-100 g/day
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4
Q

Are TGs water soluble or insoluble?

A

TGs are NOT water soluble

  • Absorption takes the most steps:
  • Pancreatic
  • Biliary
  • Intestinal
  • Intracellular
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5
Q

What is the structure of a TG? Common fatty acids?

A

H2C-O-CO-R (3) + fatty acid

90% of the fatty acids are:

  • Palmitic (16)
  • Stearic (18:0)
  • Oleic (18:1)
  • Linoleci (18:2)
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6
Q

Describe the pancreatic phase of fat absorption

A

TG degraded by lipase into 2-monoglyceride + 2 fatty acids

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7
Q

Describe the hepato-biliary phase of fat absorption

A

Solubilization

  • Bile acid monomers can form micelles
  • Can complex with cholesterol (and phospholipid)

1. Micelle Formation

  • Physical chemical complex - spherical ~3 mm, related to detergent property of bile acids

2. Bile acids

  • Detergents (polar and non-polar ends) made from cholesterol

(Critical micellar concentration 2 - 4 mM spontaneously orient into spheres)

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8
Q

What substances can micelles carry/bind?

A
  • Fatty acids
  • Monoglycerides
  • Cholesterol
  • Fat soluble vitamins
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9
Q

Describe the mucosal/absorptive (intestinal) phase of fat absorption

A
  • Micelles disaggregate at mucosal cell surface
  • Monoglycerides and fatty acids are absorbed
  • Bile acids reform micelles
  • Bile acids absorbed in ileum and recycled (entero-hepatic circulation) for reuse (4-6 times per meal)
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10
Q

Describe the intercellular/lymphatic phase of fat absorption

A
  • Re-esterification of long-chair fatty acids and monoglycerides
  • Packaged into chylomicrons (protein-cholesterol-phospholipids)
  • Transported via lymph
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11
Q

T/F: Micelle formation is essential for fat absorption

A

False

  • Medium chain TGs do not require micelles
  • Re-esterification is not essential
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12
Q

When could one benefit from the alternate fat absorption method involving medium chain TGs

A
  • Re-esterification is not essential
  • Transported via portal vein
  • Useful in diseases associated with lymph blockage (e.g. lymphoma)
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13
Q

What enzyme breaks down starch?

  • Percentage of carb intake
A

Amylase (in the brush border)

  • Starch = 60% of carbs in diet (sucrose 30%, and lactose, 10%)
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14
Q

What enzymes break down disaccharides?

  • Breakdown products?
A
  • Maltase (maltose, maltotriose) -> glucose
  • Dextrinase (dextrins) -> glucose
  • Lactase (lactose) -> galactose + glucose
  • Sucrase (sucrose) -> glucose + fructose
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15
Q

Where does major protein absorption occur?

A
  • Jejunum (major)
  • Ileum (final absorption touches)
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16
Q

Where does protein degradation occur?

A
  • Saliva
  • Stomach: gastric acid, mixing
  • Duodenum: bile and pancreatic secretions
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17
Q

What are the typical presenting features of malabsorption?

A
  • Weight loss
  • Steatorrhea
  • Vitamin deficiencies
  • Malnutrition
  • Watery diarrhea is NOT a usual presentation
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18
Q

What is steatorrhea?

  • Creatorrhea?
A
  • Steatorrhea = fat malabsorption with large, bulky, paste-like, very foul stools
  • Creatorrhea = nitrogen malabsorption (typically fixed when fat malabsorption problem fixed)
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19
Q

Causes of weight loss (broadly)?

A
  • Inadequate intake
  • Excess loss
  • Excess need
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20
Q

What conditions fall under the category of weight loss: inadequate intake (or mal-ingestion)?

A
  • Anorexia
  • Depression
  • Inability to chew
  • No food
  • No money
  • Dysphagia, etc.
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21
Q

What conditions fall under the category of weight loss: excess loss?

A
  • GI = malabsorption
  • Urinary = diabetes
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22
Q

What conditions fall under the category of weight loss: excess need?

Study These Flashcards
A

Thyrotoxicosis

23
Q

What are tests for malabsorption?

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A

- Fecal fat excretion

  • Quantitative or qualitative
  • Measure of total intestinal function

- D-xylose absorption

  • Measure of proximal* intestinal function
  • No digestion required
  • Can measure in blood, urine, breath

- B12 absorption tests

  • Measure of distal* intestinal function

- Small bowel biopsy

  • Diagnose mucosal diseases, parasites, tumors

- Small bowel x-ray

- Breath tests (e.g., bile salt)

  • Screening tests for malabsorption (e.g. carbs, bile salts)

- Pancreatic function

  • Lundh test meal
  • Secretin test
  • Response to enzyme therapy
24
Q

Tests that are not of great value for malabsorption?

Study These Flashcards
A
  • Serum carotene
  • Qualitative fecal fat
25
Describe fecal fat test
- 72 hr duration test - Measure amt of fat ingested (% of intake) * Fat intake influences fat excretion (?) - Evaluate effect of bowel resection
26
What are the effects of ileal resection on fecal fat?
If \> 100 cm (fixed) of ileum resected, will have increased fecal fat excretion
27
Describe the bile acid breath test
- Breath collected (drying tube, rubber tubing, transfer pipette) into scintillation counting vial - Measure breath radioactive CO2 specific activity - Indicates exposure of bile acids to bacteria
28
What are causes of B12 absorption? - Describe Schilling's test
Schilling's used radioactive B12 (not done anymore) - Stage 1: no addition = normal IF and ileum - Stage 2: add **intrinsic factor** =\> **pernicious anemia** - Stage 3: add **antibiotics** =\> **bacterial overgrowth** - Stage 4: add **tryspin** =\> **pancreatic insufficiency**
29
What are some causes of insufficient pancreatic enzyme activity?
- Chronic pancreatitis - Pancreatic resection - Pancreatic carcinoma - Cystic fibrosis - Zollinger-Ellison syndrome
30
What is the treatment for insufficient pancreatic enzyme activity?
- Replace enzymes - Fix pH problems
31
Describe the different protective substances that bind B12 and aid in absorptive process
- R protein binds B12 in stomach - Trypsin in pancreatic secretions digests R protein - B12 binds intrinsic factor
32
What are some causes of insufficient bile salt activity?
- Biliary obstruction (jaundice) - Blind loop syndrome - Ileal disease or resection - Zollinger-Ellison syndrome
33
How could you help diagnose pernicious anemia is you suspect it as the cause of B12 malabsorption?
Measure gastrin (should be low)
34
Treatment for insufficient bile salt activity?
- Remove obstruction - Eliminate bacteria - Give ox bile - Fix pH problems
35
List of small bowel diseases (contributing to malabsorption)
- Resection - Celiac sprue (gluten enteropathy) - Whipple’s disease - Amyloid - Lymphoma - Crohn’s disease - Many more
36
What causes Celiac Sprue? - Histological finding - Results in
- Caused by ingested toxin (gluten) - Loss of intestinal villi - Results in malabsorption
37
What is seen here?
Normal small bowel biopsy - Many villi with big absorptive surface area
38
What is seen here?
Celiac disease - Big crypts; no villi
39
What is seen here?
Celiac disease: "scalloping"
40
What is seen here?
Celiac disease: "scalloping" - Mosaic pattern (50% sensitive; 95% specific)
41
What is seen here?
Characteristics of Celiac Sprue - Absent villi - Fissuring - Scalloping - Mosaic pattern - Fissuring and ulcer
42
What causes celiac disease - Pathogenesis - Immune response centers on what - Where is it most severe
**Genetically determined**, specific immune response to antigens present in the wheat protein, gluten - Most severe in **proximal** bowel (because allergy) _Pathogenesis:_ - Gluten -\> deamidated gluten -\> activates APC -\> activates Th cell - \> activates plasma cell to produce antibodies - IgA vs. TG2 and anti-deamidated gluten - Immune response is focused on limited portion of **alpha-gliadin** - Production of epitopes recognized by CD4 T cells - Requires deamidation by tissue transpeptidase producing a 33 mer resistant to further digestion
43
How is celiac disease diagnosed?
- Stool fat - D-xylose - Serologic (antibody) tests * Anti-gliadin * Anti-endomysial (EMA) (EMA-IgA) * Anti-tissue transglutaminase (tTG) (tTG-IgA) - Small bowel biopsy\*\*\*
44
Process of diagnosing/documenting celiac disease?
- Demonstrate impaired mucosal function - Document mucosal lesion - Improvement with gluten withdrawal * Clinical - rapid * Histologic - slower
45
What causes variability in celiac disease?
- Key = length of bowel involved - Proximal only: selective iron deficiency anemia unresponsive to oral iron therapy * Iron reabsorbed in duodenum!! - Large amount: pan malabsorption * Diarrhea, weakness, weight loss, anemia, tetany, bleeding (vitamin K deficiency), etc.
46
What key nutrients are absorbed in: - Dudodenum - Jejunum - Ileum
- Duodenum: Iron (Fe) - Jejunum: folate - Ileum: Vit B6 (double check?)
47
Therapy for celiac disease?
**- Gluten free diet** * No: wheat, rye, barley * Yes: rice, oats, corn **- Replace vitamins**
48
What causes lactase deficiency - Mechanism - Genetic?
- Lack of brush border disaccharidase - Congenital - Acquired * Ethnic * Mucosal disease (e.g., viral gastroenteritis)
49
How to diagnose lactase deficiency?
- History (e.g., can not drink milk) - Lactose tolerance test * Symptoms after large lactose drink: diarrhea, cramps, gas, borborygmi; no rise in blood glucose - Breath hydrogen test * Increase after lactose ingestion as lactose gets to colon
50
Lactose is normally broken down into what products? - What about in lactase deficiency?
- Normally -\> glucose + galactose and absorbed in small intestine - In lactase deficiency, converted into lactic acid and other products (H2 and CO2) by bacteria in the colon; osmotic diarrhea as well (fluid pulled into colon)
51
What does someone have if they think they are allergic to mushrooms?
Trehalase (a disaccharidase) deficiency!
52
Bacterial overgrowth: - Causes/predispositions - Pathogenesis - Result
_Causes:_ - Diverticula - Motor abnormalities of the small bowel - Surgical bypass, etc. _Pathogenesis_ - Bacterial compete for luminal contents (Vitamin B12, bile acids [deconjugate]) _Results in_: Malabsorption - Caused by abnormal populations of bacteria in the small intestine (stasis is implied)
53
Test for bacterial overgrowth?
- Schilling test before and after antibiotics - Fecal fat before and after antibiotics - Bile salt breath test - D-xylose breath test - Response to antibiotic therapy

MS2 GI (26 decks)

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