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Medicine > malabsorption > Flashcards

malabsorption Flashcards

1
Q

Proximal SI absorptives?

A

Calcium
Iron
Folic acid

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2
Q

Distal SI absorptives?

A

Vitamin B12

Bile acids

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3
Q

Primary bile acids

A

Cholic acid
Chenodeoxycholic acid
Synthesized in the liver from cholesterol (~500mg/d)

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4
Q

Secondary bile acids

A

Deoxycholic acid
Lythocholic acid
Synthesized from primary bile acids in the intestine by bacterial enzymes.

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5
Q

Conjugation of BA (to what and where)

A

taurine
glycine
liver
terminal ileum active Na+ absorption

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6
Q

Deconjugation BA (how and where)

A

colonic bacteria

reabsorb in colon and jejunum

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7
Q

Fat Absorption- Intraluminal phase

A

Lipolysis accure from stomach to jejunum
20-30% by gastric lipase (pH 4.5-6)
70-80% in duodenum/jejunum by pancreatic lipase

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8
Q

Impaired lipolysis

A

lipase secretion reduction:
Chronic pancreatitis
cystic fibrosis

PH:
Gastrinoma

lipolysis can be maintained by 5% of max pancreatic lipase secretion

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9
Q

micelle structure

A

inner- fatty acids
intermidiate- glycerol
out- conjugated bile salts (lack of those will damage micelle formation)

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10
Q

Fat Absorption- Mucosal & Delivery phase

A

Lipids enter the enterocytes

re-esterification to triglycerides

creation of Chylomicrons: 
β-lipoprotein
triglycerides
Cholesterol
phospholipids

leave by lymphatic system

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11
Q

Abetalipoproteinemia

A

Failure in chylomicron formation prevents exit of lipids

histological Lipid- laden enterocytes

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12
Q

Medium Chain triglycerides

A

coconut oil

Do not require pancreatic lipolysis as they can be absorbed intact

Absorbed more efficiently than LCTs

do not require chylomicron formation to exit

exit is via the portal vein and not via lymphatis

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13
Q

Short Chain Fatty Acids

A

primarily acetate, propionate, and butyrate

Butyrate is the primary nutrient for colonic epithel

stimulate colonic NaCl and fluid absorption

Diversion colitis

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14
Q

Carbohydrate Absorption

A

only in the small intestine

only as monosaccharides

Disaccharides & starch are digested by pancreatic amylase & brush-border disaccharidase

Na-dependent transporter (SGLT1) Absorption

Lactase deficiency

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15
Q

Protein Absorption

A

only di- and tripeptides absorption

pepsin and trypsin

disorders are rare

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16
Q

Trypsin

A

Secreted as trypsinogen by the pancreas

Activated by brush-border enzyme enterokinase

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17
Q

Pepsin

A

secreted as pepsinogen from gastric chief cells

Activates by pH < 5

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18
Q

Water soluble vitamins

A

dietary & microbiome
absorption occurs via specific carriers, mostly in the proximal SI
(except for B12)

19
Q

vitamins B1-12 names

A

1- thiamine
2- riboflavin
3- niacin

5- pantothenic acid
6- pyridoxine
7- biotin

9- folate
12- cobalamin

C- ascorbic acid

20
Q

cobalamin

A

bound to proteins

chewing and pepsin hydrolyz to free Cbl

stomach-
haptocorrin together are resistant to acid and pepsin digestion

upper small intestine-
trypsin and chymotrypsin release from HC
binds to intrinsic factor (synthesized by parietal cells)
resistant to digestive enzymes present in upper GI

terminal ileum-
specific receptor uptake
IF degraded in lysosome

circulation-
transcobalamin II carries Cbl to liver

21
Q

Fat soluble vitamins

A

ADEK
incorporation into micelles => package into chylomicrons
Deficiencies can be due to fat malabsorption

22
Q

iron

A

no excerition
10% absorbed mostly in proximal small intestine
ferrous (Fe2+) > ferric (Fe3+)
+3 to +2 by Ascorbic acid (facilitate absorption)

23
Q

Water Absorption

A 
92% small intestine, rest in colon
Diffusion through membrane
Water channels (aquaporins)
Transporters
highly dependent on Na and glucose absorption
24
Q

Lactase Deficiency

A

Lactose is a disaccharide present in milk

lactase present at Brash- border

Primary: genetically determined
Secondary: associated with small intestine mucosal diseases (celiac, etc.)

25
Q

Pernicious Anemia

A

Autoimmune
parietal cell destruction - prevents B12-IF complex formation

Anti-IF
Anti-parietal cells (reacts with H/K ATPase in parietal cells

26
Q

Pernicious Anemia symptoms

A

lemon-yellow waxy pallor
symptomatic anemia
smooth tongue
neurologic deficits

27
Q

Pernicious Anemia treatment

A

parentral B12

28
Q

Hereditary Hemochromatosis

A

accumulation of Iron due to increased absorption

29
Q

Hereditary Hemochromatosis etiology

A

HFE mutation => decreased Hepcidin levels => increase absorption

30
Q

Hereditary Hemochromatosis treatment

A

phlebotomies

iron cheletors

31
Q

celiac morphology

A

villi flattening and increased mucosal lymphocytic infiltration

32
Q

celiac location

A

mainly the proximal small intestine

33
Q

celiac trigger

A

Abnormal immunologic response to gliadin

34
Q

Small Intestine Bacterial Overgrowth (SIBO) etiology

A

Anatomical stasis- diverticuli, fistulas and strictures, intestine bypass

Functional stasis- diabetic dysmotility, scleroderma

35
Q

Small Intestine Bacterial Overgrowth (SIBO) cause

A

Colonic- type bacterial proliferation in the SI

36
Q

Small Intestine Bacterial Overgrowth (SIBO) Symptoms

A

Diarrhea
bloating
Iron deficiency
Steatorrhea: colonic bacteria in small intestine -> deconjugation of bile acids
Macrocytic anemia: cobalamin consumption by the bacteria, Folate level is increased due to production by the bacteria

37
Q

Small Intestine Bacterial Overgrowth (SIBO) Treatment

A

Antibiotics

38
Q

Short bowel syndrome etiology

A

result of extensive SI resection (Crohn’s, mesenteric ischemia)
In rare cases- congenital

39
Q

Short bowel syndrome symptoms depend on

A

length of, and identity of specific segment that was resected
Residual disease in the remaining segment

40
Q

Short bowel syndrome symptoms

A

Multiple nutritional deficiencies

Multifactorial diarrhea

Renal calcium oxalate stones: Increased fatty acid bind calcium -> increase in free oxalate -> increased absorption

Increase in cholesterol gallstones: Decreased bile acid pool size -> cholesterol supersaturation

Gastric acid hypersecretion

41
Q

Short bowel syndrome treatment

A

Oral rehydration solutions, MCTs, vitamin

TPN

GLP-2 analogue (Gattex, atrophy of remaining intestine)

42
Q

Bariatric surgeries types

A

restrictive:
vertical sleeve
gastric band

malabsorptive:
roux-en-y bypass
deudenal switch

43
Q

Roux-en-Y Gastric Bypass

A

demand daily vitamins postoperatively

44
Q

Roux-en-Y Gastric Bypass deficiencies risk

A

Vitamin B12: low IF

fat-soluble vitamins A, D, E, and K.

Fe, B9, Ca: normally absorb mainly in duodenum & proximal jejunum.
Ca deficiency exacerbates by vitamin D deficiency

Prolonged vomiting may result in thiamine (vitamin B1) deficiency, which can lead to Wernicke’s encephalopathy

Medicine (17 decks)

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