Term
| Describe the journey of triglycerides and how does it differ from that of proteins/carbs |
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Definition
Triglycerides are digested in the pancreas to FAs/monoglycerides, become part of the mixed micelle with bile acids in the liver, go to the brush border of the jejunal mucosa to partake in triglyceride synthesis/chylomicron formation and are transported to the lymphatics as chylomicrons and then to blood
Proteins and Carbs digestion starts from the pancreas and => the jejunal mucosa as AAs and monosaccharides. |
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Term
| T/F: the body is very efficient at absorbing 100% of nutrients at the small bowel |
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Definition
False:
Nutrients
Fat 93-95% of triglyceride
Starch 80-95% depending on type
Disaccharides 96-98%
Protein 95-99%
Minerals
Iron 6-20% depending on body iron status |
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Term
| What happens to leftover carbs in the colon? |
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Definition
| Colon scavenges malabsorbed carbohydrates as short chain fatty acids, products of bacterial fermentation |
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Term
| T/F: diarrhea and malabsorption go hand in hand |
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Definition
False - malabs is only a small part of diarrhea
Bowel disease may => diarrhea if 1. Enough osmotically active molecules reach the colon
2. Malabsorbed molecules stimulate colon/SB ion secretion (long-chain fatty acids, bile acids) |
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Term
| Signs of vitamin/mineral deficiencies: |
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Definition
glossitis, cheilosis (iron/B vitamins)
acrodermatitis (zinc)
dry skin and hair (essential fatty acids)
anemia microcytic - iron deficiency
macrocytic - folate/B-12 deficiency
osteopenia/osteoporosis Vit D/calcium
night blindness Vitamin A
easy bruising Vitamin K |
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Term
| Clues to nutrient malabsorption: |
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Definition
Weight loss, fatigue, “out of gas”
Intake of excess calories without weight gain
Diarrhea: bulky, oily stools (fat)
liquid stools (carbohydrates)
Flatus |
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Term
| Acrodermatitis what is it due to? |
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Definition
| Zn deficiency: Loss of hair, skin rash and diarrhea due to zinc deficiency |
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Term
| A patient with pancreatitis presents with? |
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Definition
Luminal maldigestion (fat) => steatorrhea due to no pancreatic lipases and lack of conjugated bile acids (salts) from the liver
No small intestinal back-up available |
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Term
| What's the etiology of chronic pancreatitis, and how can we see the damage? |
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Definition
Often due to long-standing alcohol use
Marked destruction of ducts/acini
Reduced secretion of digestive enzymes, fluid, bicarbonate
Lipases most affected
Anatomic damage assessed by ERCP or endoscopic ultrasound (EUS) or pancreatic calcifications on x-rays |
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Term
| Why would you get edema/hypoproteinemia with chronic panc? |
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Definition
| Due to malnutrition with decreased hepatic synthesis of albumin/serum proteins |
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Term
| 3 Mechanisms of pancreatic insufficiency: |
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Definition
1) Bile salt deficiency: Loss of terminal ileum loss of bile salts in stool, insufficient bile salts
Bacterial overgrowth: Deconjugation and loss of bile acids
Gastric hypersecretion: Acid inactivation of pancreatic enzymes |
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Term
| Mucosal maldigestion - example? |
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Definition
lactase deficiency
Lactase: enterocyte brush-border disaccharidase found in nursing mammals.
Lactase splits lactose in milk to the monosaccharides glucose and galactose for absorption.
Normally little of the enzyme is made by villus enterocytes after weaning
exceptions are groups of humans who exhibit unusual persistance of lactase throughout adulthood
northern Europeans and other "dairying" cultures
Symptoms occur upon ingestion of lactose by lactase-deficient individuals. |
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Term
| Why is it that you get flatus with lactase deficiency? |
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Definition
| If you have enough you abs >80%, but if you don't you abs <50% of lactose and that goes into the colon where most of the bacteria live => 6-20g of malabs lactose => FLATUS! >20g => flatus + diarrhea |
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Term
| Mucosal maldigestion/malabsorption examples: |
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Definition
| celiac sprue, bacterial overgrowth |
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Term
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Definition
It's a patchy disease in the proximal bowel, Immune-mediated destruction of enterocytes in response to ingestion of the protein gluten found in wheat and certain other grains. A fraction termed gliadin contains the immunogenic material
Villi are destroyed but you still have CRYPTS
Small intestinal villi are damaged or destroyed - "flat gut" appearance.
Mature digesting and transporting enterocytes are virtually absent. |
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Term
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Definition
| Characteristic antibodies used in diagnosis: IgA antibodies to tissue transglutaminase or gliadin. |
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Term
| What's responsible for the destruction in CS? |
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Definition
| T-cells, not the antibody |
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Term
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Definition
| no villi but you find massively enlarged crypts |
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Term
| CS Clinical manifestations |
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Definition
Weight loss, often with increased appetite
Bulky, oily stools – steatorrhea - fat malabsorption
Flatus/frothy stools – carbohydrate malabsorption
Microcytic Anemia – deficiencies of iron b/c you KNOCK OUT THE DUODENUM!, folate
Osteopenic bone disease – Vitamin D and calcium malabsorption
Edema/hypoproteinemia – protein deficiency and malnutrition
Cheilosis and glossitis – B vitamin deficiencies |
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Term
| What causes bacterial overgrowth and what as a result is lost? |
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Definition
anatomic or motility factors.
Clinical consequences:
Deconjugation of bile acids by bacterial enzymes
Loss of deconjugated bile acids in stool
Decreased bile acid pool - not enough for lipid digestion/absorption
Damage to enterocytes by bacteria |
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Term
| Clinical consequences of bacterial overgrowth? |
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Definition
Intraluminal consumption of nutrients by bacteria (competition)
Carbohydrates, amino acids
Vitamin B-12, iron
Damage to small bowel enterocytes causing a sprue-like histologic appearance
Mild to severe generalized malabsorption |
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Term
| Cheap diagnostic tests for malabsorption? |
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Definition
Screening tests – simple, cheap, fast
Stool smear with fat stain
CBC for evidence of anemia
Cholesterol/carotene blood levels
Stool osmotic gap for carbohydrates
Weight loss/clinical clues |
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Term
| What does a Sudan stain show in pancreatitis? |
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Definition
| Big fat globules triglycerides…if they’re eating normally then you have probably fat malabs |
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Term
| Quantitative tests for malabs? |
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Definition
Quantitate nutrient malabsorption: messy, take time, accurate and quantitative
72-hour fecal fat
D-xylose excretion (monosaccharide)
Schilling’s test for B-12 absorption (no longer available)
Breath hydrogen test (carbohydrate) |
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Term
| What is the D-xylose test? |
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Definition
| monosacch not require splitting. Can measure in blood/urine and has been standardized. So this is good for seeing if px is malabs sugar. |
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Term
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Definition
Give labeled B12 – load up body stores and you see excretion in urine!
requires good renal fxn |
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Term
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Definition
Principle:
malabsorbed sugar passes into colon
bacteria produce hydrogen gas
H2 diffuses into blood and is excreted by lungs
Practice:
Administer 25-50 grams of glucose or other sugar orally
Measure hydrogen in exhaled breath at 2-4 hours |
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Term
| How can a patient have both fat and B12 malabs? |
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Definition
Luminal maldigestion due to
(have to involve terminal ileum) ileal loss of bile salts and bile salt deficiency
Bacterial overgrowth:
deconjugation of bile acids
and bacterial uptake of B-12 |
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Term
| Fat and d-xylose malabsorption |
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Definition
| due to Mucosal malabsorption: CS, Bacterial overgrowth, Severe Crohn’s disease, Whipple’s disease |
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Term
| Evaluating malabs...which tools? |
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Definition
Radiographs of the small bowel to delineate anatomy
Endoscopic retrograde cholangiopancreatography (ERCP) to define the anatomy of biliary and pancreatic ducts
Pancreatic secretory function tests
Small bowel biopsy and/or antibody tests for celiac sprue
Quantative small bowel bacterial culture, bile acid or glucose breath tests for bacterial overgrowth |
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