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Flashcards in large intestine Deck (40):
1

failure of neural crest cell migration
dysfunctional Auerbach (muscularis externa layer) + Meissner plexus (submucosal layer) → abnormal peristaltic waves

Hirschsprung disease

2

congenital megacolon with meconium ileus or if less severe, chronic constipation as infant (chronic distention)

Hirschsprung disease

3

twisting of colon around mesentary → ischemia

volvulus

4

most common location of volvulus in elderly (most commonly affected by volvulus)

cecum or sigmoid colon

5

most abundant bacterial flora in large intestine

#1 bacteroides fragilis
#2 E. coli (enterobacteraciae)
other enterobacteraciae:
proteus mirabilis
proteus vulgaris
salmonella
shigella
klebsiella pneumoniae

6

complication of obstruction of appendicitis with:
adults: fecalith (fecal stone)
kids: viral infection (hyperplasia of lymphoid tissue= MALT tissue)

appendicitis

7

N/V
diffuse periumbilical pain → later, pain localizes to RLQ (McBurney's point)
rebound tenderness in RLQ
leukocytosis on CBC

appendicitis

8

McBurney's point

2/3 the way from umbilicus to ASIS

9

confirm diagnosis of appendicitis

r/o ectopic pregnancy with female (serum bHCG)
adults: CT scan
kids or pregnant: US

10

line anus that marks end of endoderm and beginning of ectoderm (squamous cell)

pectinate line

11

pathology proximal to pectinate line

internal hemorrhoids: not painful, may bleed
tx: can band → necrosis

12

sensory + arterial blood supply + venous drainage above and below pectinate line

above: no sensation, superior rectal artery (from IMA), superior rectal vein (to IMV)
below: sensation, inferior rectal artery (from pudendal artery - not IMA), inferior rectal vein (to internal pudendal vein → to internal illiac vein→to IVC)

13

cancer above pectinate line is most likely

adenocarcinoma (rectal)

14

pathology distal to pectinate line

external hemorrhoids: very painful
tx: numbing agent -symptomatic relief

15

cancer below pectinate line is most likely

squamous cell carcinoma (anus)

16

biggest risk factor for squamous cell carcinoma of anus

HPV 16, 18, 31

17

inflammation of perianal region + rectum due to fecal matter in area for an extended period of time
associated with ulcerative colitis
tx: topical steroids

proctitis

18

most common type of polyp in colon - found in rectum or rectosigmoid

hyperplastic polyp

19

polyp with no precancerous risk (benign)
removed during colonoscopy since need bx to prove not cancerous

hyperplastic polyp

20

types of adenomatous polyp (neoplastic - precancerous polyp for adenocarcinoma)

tubular adenomas (lots of glands)
tubulovillous adenomas
villous adenomas (most VILLainOUS - most precancerous, lots of finger-like projections)

21

child

juvenile polyps
if one: no malignant potential
if many: juvenile polyposis syndrome →↑ risk adenocarcinoma

22

AD
multiple benign hamartomas in GI tract (excess accumulation of normal tissue that is located at the site of growth)
hyperpigmentation: lips, mouth, hands, genitalia
↑ risk cancer (50% by 60 yo): colorectal cancer, small intestinal, stomach, pancreatic, breast, ovarian, uterine

Peutz-Jeghers Syndrome

23

risk factors for colon cancer

IBD: UC > chron's
smoking
high fat/low fiber diet
alocohol use
obesity
adenomatous polyps (villous adenomatous polyps greatest risk)
strep bovis bacteremia: 50% of colon cancer patients colonized it in their stool
polyposis syndrome: FAP, HNPCC, Peutz-Jeghers syndrome, juvenile polyposis

24

fatigue, weight loss, LAD, night sweats
abdominal pain, bowel obstruction → N/V
change in bowel habits if L-sided colon affected: "pencil-thin stools"
hematochezia: if rectosigmoid region affected
IDA - chronic GI bleed: if R-sided colon

colon cancer

25

incidental finding of anemia in >50 yo

screen for colon cancer (GI bleed - most commonly R. sided cancer)

26

diagnosis of colon cancer

colonoscopy: >50 yo
fecal occult blood testing
barium enema
flexible sigmoidoscopy
confirmation: tissue bx

27

"apple-core" lesion with barium enema

narrowing of lumen of colon
suggest colon cancer

28

CEA is a tumor marker for

colon cancer
nonspecific: but useful for monitoring for recurrence after treatment for colon cancer

29

AD (germline) mutation in APC gene
1000s of polyps begin at young age
100% progress to colorectal cancer unless colon is resected

familial adenomatous polyposis (FAP)

30

FAP (mutation of APC gene, 1000s of polyps) + malignant CNS tumors (medulloblastoma)

turcot syndrome

TURcot = TURban (brain tumors)

31

FAP (mutation of APC gene, 1000s of polyps) + bone and soft tissue tumors (lipomas, retinal hyperplasia)

Gardner syndrome

lumpy vegetables in garden = lumps, bumps all over body

32

AD mutation in DNA mismatch repair gene → microsatelite instability pathway
colorectal cancer DOESN'T arise from polyp (nonpolyposis colorectal cancer)
PROXIMAL colon cancer (vs 50% of colon cancer in distal 1/3 -distal to splenic flexure)

Heriditary nonpolyposis colorectal cancer (HNPCC/Lynch syndrome)

33

>60 yo with many blind pouches in sigmoid colon
usually asymptomatic or
vague pain in LLQ RELIEVED with defecation or
painless rectal bleeding

diverticulosis

34

true diverticula

outpouching of all three layers of gut wall
example: meckel diverticulum

35

false diverticula

outpouching of only mucosa + submucosa due to weak spots in muscularis externa (where vasa recta perforate muscularis externa)
example: colonic diverticulum

36

diagnosis

barium enema

37

LLQ pain (sigmoid colon)
fever
elevated WBC count
rectal bleeding
constipation due to inflammation in colon
peritonitis (if perforation)

diverticulitis

38

free air in abdomen (below diaphragm) on CT scan

perforated bowel from:
appendix
PUD
diverticulitis

39

treatment of acute flare of diverticulitis

antibiotics: metronidazole (anaerobic bacteria) + TMP-SMX or FQ (ciprofloxacin)

40

screening colonoscopy guidelines

begin at 50 yo
if + family history: begin at 40 yo or 10 yr before youngest 1st degree relative diagnosis
if FAP: every year from 10-12 yr to 35-40 yr
if Lynch syndrome: begin at 20-25 yo or 10 yr before youngest relative diagnosis

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