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Block 7 - GI > Intestine Path > Flashcards

Intestine Path Flashcards

1
Q

How can you differentiate the different parts of the small intestine?

A

duodenum - Brunner’s glands
jejunum - lacks Brunner’s and Peyer’s patches
ileum - Peyer’s patches

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2
Q

What increases the absorptive surface of the small intestine?

A

villi, microvilli, and plicae circulares (folds in submucosa)

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3
Q

How does the epithelial lining change in the colon and rectum?

A

shaped into tubular structures called crypts or glands, no villi

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4
Q

What do all cells in the large intestine have in common?

A

proper polarity - nuclei at bottom of cells

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5
Q

What is ischemic enterocolitis?

A

reduction, interruption, obstruction of blood supply

often result of decreased systemic perfusion or anatomic occlusion

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6
Q

Where does ischemic injury usually occur within the GI tract?

A

watershed areas where collateral arteries small and narrow

mostly left colon (splenic flexure)

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7
Q

How does ischemic enterocolitis usually resolve?

A

usually mild and on their own - accessory supply from retroperitoneal portions
minority are gangrenous

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8
Q

What are the causes of acute and chronic cases of ischemic enterocolitis?

A

acute - thrombi/emboli - hemorrhagic due to dual blood supply
chronic - atherosclerosis

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9
Q

What are the major variables in ischemic bowel dz?

A

severity of vascular compromise
period during which it develops
vessels affected

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10
Q

What are the two watershed zones?

A

sup and inf mesenteric arteries

inf mesenteric and hypogastric arteries

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11
Q

How does microvascular anatomy affect ischemic bowel dz?

A

intestinal capillaries run from crypt to surface and hairpin turn before emptying
allows blood to supply crypts (w stem cells) but leaves surface epithelium vulnerable to ischemic injury - look for hyperproliferative crypts w surface atrophy as morphological hallmark

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12
Q

What are predisposing conditions for bowel infarcts?

A 
arterial thrombosis
arterial embolism
venous thrombosis
obstruction
non-occlussive ischemia (low flow)
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13
Q

What are the three categories of ischemic bowel injury?

A

mucosal infarct
mural infarction - mucosa and submucosa
transmural infarction - acute occlusion of major mesenteric A

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14
Q

What do you see with transmural bowel infarctions?

A

purple-red hemorrhagic, then blood in lumen and wall edematous and thickened
coagulative necrosis of muscularis propria w/i 1-4 days
possible serositis

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15
Q

What are the possible consequences of transmural bowel infarctions?

A

perf

mucosal barrier breaks down - bacteria enter circulation –> sepsis

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16
Q

What do the margins of ischemic damage look like in the bowel?

A

arterial occlusion - sharply defined

venous occlusion - less distinct

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17
Q

What generally causes mucosal and mural infarctions?

A

hypoperfusion

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18
Q

What do you see with mucosal or mural bowel infarcts?

A 
often patchy lesions
hemorrhagic mucosa - maybe ulcers
thickened edematous bowel wall
no serosal hemorrhage or serositis
psuedomembranes may form
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19
Q

When are mucosal and mural bowel infarcts completely reversible?

A

as long as muscularis propria spared and hypoperfusion corrected

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20
Q

What is diverticulosis?

A

blind pouch leading off GI tract - lined by mucosa communicating with gut lumen

21
Q

What is the difference between congenital and acquired diverticulosis?

A

congenital - have all 3 layers of bowel wall

acquired - lack or have attenuated musc. propria, mostly in sigmoid

22
Q

What are examples of congenital diverticulum?

A

meckel, normal appendix

23
Q

What are examples of acquired diverticulum?

A

zenker, colontic

24
Q

What two influences contribute to the genesis of diverticula?

A

exaggerated peristaltic contractions w elevation of luminal pressure
inherent anatomy of colon - incomplete outer longitudinal muscle gathered into tenia coli and focal defects where neurovascular bundles penetrate

25
Q

Why are diverticula associated with Western diets?

A

low fiber causes prolonged transit time and increased intraluminal pressure associated w low volume stools

26
Q

What are some symptoms of diverticula?

A

sensation of inability to empty rectum, alternating constipation and diarrhea

27
Q

What are complications of diverticula?

A

inflamation or inf

peritonitis, hemorrhage, perf w abscess

28
Q

What other conditions can diverticula resemble?

A

carcinoma radiologically

appendicitis clinically

29
Q

What types of bowel obstructions are there?

A

mechanical or functional

majority in small bowel - strangulated (surgical emergency) or not

30
Q

What are the most common causes of bowel obstruction?

A

mechanical - adhesion, hernia, intussusception, volvulus

31
Q

When do adhesions develop?

A

when peritonitis heals

32
Q

Where do hernias most often occur?

A

inguinal and femoral canals
umbilicus
site of surgical scars

33
Q

What is a hernia?

A

portions of intestine or ab fat tissue bulge out - covered by thin membrane, can become trapped or strangulated

34
Q

What is intussusception?

A

segment of intestine invaginates into adjoining intestinal lumen - intraluminal tumor?

35
Q

What is volvulus?

A

twisting of intestine loop around mesenteric attachment site, mostly in small bowel

36
Q

What are complications of small bowel obstruction?

A

sepsis, intra-ab abscess, wound dehiscence, aspiration, short bowel syndrome from multiple surgeries, death

37
Q

What are signs and symptoms of small bowel obstruction?

A 
pain
nausea and vomiting
diarrhea then constipation
fever and tachycardia
previous surgery or XRT
hx of malignancy
38
Q

What causes Hirchsprung dz?

A

absence of ganglion cells - segment narrows

RET gene mutations that inactivate RET receptor kinase

39
Q

What indicates diarrhea?

A

stool weights above 250-300 gms/day

40
Q

What is the basic pathogenesis of all diarrhea?

A

reversal of normal net absorption of water and electrolytes to secretion - by osmotic force or active secretion

41
Q

What are acute causes of diarrhea?

A

acute infections
drugs
food allergies
IBD

42
Q

What are chronic causes of diarrhea and how long is needed to be considered chronic?

A 
3 weeks
IBD
IBS
chronic infections
malabsorption syndromes
43
Q

What is the most important mechanism of diarrhea?

A

malabsorption - accumulation of unabsorbed material leads to steatorrhea
will abate w fasting

44
Q

What can cause malabsorption diarrhea?

A

giardia
celiac sprue
lactase def

45
Q

What kind of diarrhea is c. difficile responsible for?

A

antibiotic associated diarrhea and colitis = psuedomembranous, caused by exotoxins A & B

46
Q

What is celiac sprue?

A

immune response to glutin controlled by CD4 T cells

predisposing HLA-DQ2 and HLA-DQ8

47
Q

How is celiac sprue diagnosed?

A

confirm by biopsy from 2nd part of duodenum - villous atrophy, lymphocytes, crypt hyperplasia
AGA or EMA antibodies present

48
Q

What is Whipples dz?

A

systemic illness from tropheryma whippelii - arthritis, weight loss, diarrhea, encephalopathy, lymphadenopathy, steatorrhea

49
Q

What are microscopic findings in whipples?

A

foamy macrophages in lamina propria w PAS+ organisms

Block 7 - GI (28 decks)

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