10 - Large Intestine

Question 1

entamoeba histolytica infection in colon

Answer 1

most often in cecum and ascending colon
cause flask shaped ulcers
amoeba look sorta like macrophages
may penetrate vessels and infiltrate liver > amebic abscess

Question 2

flask shaped ulcer

Answer 2

entamoeba histolytica in colon

Question 3

presentation of entamoeba histolytica

Answer 3

abd pain, bloody diarrhea, wt loss

can occasionally lead to acute necrotizing colitis and megacolon

Question 4

tx for entamoeba histolytica

Answer 4

metronidazole

Question 5

pseudomembranous colitis - cause and pathogenesis

Answer 5

c diff (usually, can also be salmonella, c perfringens, staph aureus)
abx disrupt flora > c diff overgrowth > toxins > disruption of epithelial cytoskeleton > tight jxns lost > cytokines > apoptosis

Question 6

MC abx cause of pseudomembranous colitis

Answer 6

3rd gen cephalosporins

Question 7

micro path of pseudomembranous colitis

Answer 7

“volcano eruption” of neutrophils and dead cells into lumen

inc chronic inflammatory cells in lamina propria

Question 8

sx of pseudomembranous colitis

Answer 8

fever, leukocytosis, abd pain/ cramps, hypoalbuminemia, watery diarrhea, dehydration, may have fecal leukocytes or occult blood

Question 9

tx of pseudomembranous colitis

Answer 9

metronidazole or vanc

Question 10

2 inflammatory bowel diseases

Answer 10

Crohn disease and ulcerative colitis

Question 11

difference between Crohn and ulcerative colitis

Answer 11

Crohn - regional enteritis in any area of GI, typically transmural. “Skip lesions”, transmural inflammation, and fissures seen. strictures common

ulcerative - severe ulcers limited to colon/rectum involving mucosa and submucosa. Continuous colonic involvement rectum->proximal, ulcers and pseudopolyps

Question 12

epi of IBD

Answer 12

F > M
common in teens/early 20s
caucasian, ashkenazi jews

Question 13

pathogenesis of IBD

Answer 13

genetic susceptibility > release of TNF / cytokines in response to stimulus > inc tight jxn permeability > more stimulating material comes in (bacteria stuff) > pos feedback loop

Question 14

tobacco and IBD

Answer 14

tobacco use inc risk of Crohn, dec risk of ulcerative colitis

Question 15

Crohn dz micro path

Answer 15

cryptitis and crypt abscess > destruction
abrupt transitions btwn ulcers and nl mucosa
distorted architecture due to constant remodeling
epithelial metaplasia > gastric antral appearing glands / foveolar metaplasia
**noncaseating granuloma is hallmark - can be in mesenteric LN or cutaneous (metastatic)

Question 16

path hallmark of Crohn’s

Answer 16

noncaseating granulomas

Question 17

extra colonic manifestations of IBD

Answer 17

migratory polyarthritis, sacroiliitis, akylosing spondylitis, uveitis, skin lesions, pericholangitis, primary sclerosing cholangitis

Question 18

which IBD is assoc w/ colonic dilation / toxic megacolon?

Answer 18

ulcerative colitis

Question 19

ulcerative colitis micro path

Answer 19

similar to crohn in crypts
no inflammation beyond submucosa really
no granulomas

Question 20

ulcerative colitis clinical features

Answer 20

relapsing episodes of bloody diarrhea w/ stringy mucoid material, lower abd pain, temporarily relieved by defecation

Question 21

monitoring for colitis assoc neoplasia

Answer 21

start 8 yrs after dz initiation (unless you have primary sclerosing cholangitis - start right away)

Question 22

diverticulosis pathophys

Answer 22

low fiber diet > chronic constipation > inc intraluminal pressure > muscular hypertrophy > hernation of mucosa thru muscle wall

Question 23

where are diverticular most common in colon?

Answer 23

sigmoid

Question 24

sx of diverticulosis

Answer 24

most asymptomatic
other have intermittent cramping, continuous lower abd discomfort, constipation, distention, sensation of never being able to completely empty rectum

Question 25

diverticulitis - tx

Answer 25

resolves spontaneously, rare to need surgery

high fiber diet improves sx of diverticulosis

Question 26

MC neoplastic polyp

Answer 26

adenoma (could become CA)

Question 27

colonic adenoma = ___ dysplasia

Answer 27

mild

Question 28

prevalence of adenoma polyps in western world

Answer 28

50% by age 50

Question 29

surveillance for polyps/colon neoplasia

Answer 29

50 or 10 yr before youngest time of dx for relative

Question 30

histologic hallmark of colonic adenoma

Answer 30

nuclear hyperchromasia, elongation, and stratification

Question 31

pedunculated and sessile adenomas - match w/ morphology

Answer 31

pedunculated - tubular adenoma

sessile - villous adenoma

Question 32

which type of adenoma - tubular or villous - is more likely to invade?

Answer 32

villous

Question 33

MC malignancy of GI tract

Answer 33

adenoCA of colon

Question 34

2 distinct genetic pathways for developing colon adenoCA

Answer 34

APC/beta catenin - WNT gene, “classic” adenoCA sequence

microsatellite instability pathway - defects in DNA mismatch repair

Question 35

gross morphology of colon cancer

Answer 35

in proximal colon, rarely causes obstruction
distal , annular w/ napkin ring constrictions > luminal obstruction
both grow into bowel wall and make a firm palpable mass

Question 36

micro path of colon cancer

Answer 36

invasion w/ strong desmoplastic response
poorly diff cells - few glands
some mucin production > poor prognosis

Question 37

presentation of colon cancer

Answer 37

proximal: fatigue/weakness due to iron deficiency anemia
distal: occult bleeding, changes in bowel habits, cramping/discomfort in LLQ

Question 38

colon cancer prognosis

Answer 38

poorly diff and mucinous tumors have poor prognosis

2 important prognostic factors - depth of invasion, LN metastases

Question 39

where does colon cancer like to metastasize?

Answer 39

regional LNs, lungs, bones, liver