large intestine

Question 1

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

Answer 1

Hirschsprung disease

Question 2

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

Answer 2

Hirschsprung disease

Question 3

twisting of colon around mesentary → ischemia

Answer 3

volvulus

Question 4

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

Answer 4

cecum or sigmoid colon

Question 5

most abundant bacterial flora in large intestine

Answer 5

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

Question 6

complication of obstruction of appendicitis with:

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

Answer 6

appendicitis

Question 7

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

Answer 7

appendicitis

Question 8

McBurney’s point

Answer 8

2/3 the way from umbilicus to ASIS

Question 9

confirm diagnosis of appendicitis

Answer 9

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

Question 10

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

Answer 10

pectinate line

Question 11

pathology proximal to pectinate line

Answer 11

internal hemorrhoids: not painful, may bleed

tx: can band → necrosis

Question 12

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

Answer 12

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)

Question 13

cancer above pectinate line is most likely

Answer 13

adenocarcinoma (rectal)

Question 14

pathology distal to pectinate line

Answer 14

external hemorrhoids: very painful

tx: numbing agent -symptomatic relief

Question 15

cancer below pectinate line is most likely

Answer 15

squamous cell carcinoma (anus)

Question 16

biggest risk factor for squamous cell carcinoma of anus

Answer 16

HPV 16, 18, 31

Question 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

Answer 17

proctitis

Question 18

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

Answer 18

hyperplastic polyp

Question 19

polyp with no precancerous risk (benign)

removed during colonoscopy since need bx to prove not cancerous

Answer 19

hyperplastic polyp

Question 20

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

Answer 20

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

Question 21

child

Answer 21

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

Question 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

Answer 22

Peutz-Jeghers Syndrome

Question 23

risk factors for colon cancer

Answer 23

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

Question 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

Answer 24

colon cancer

Question 25

incidental finding of anemia in >50 yo

Answer 25

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

Question 26

diagnosis of colon cancer

Answer 26

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

Question 27

"apple-core" lesion with barium enema

Answer 27

narrowing of lumen of colon | suggest colon cancer

Question 28

CEA is a tumor marker for

Answer 28

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

Question 29

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

Answer 29

familial adenomatous polyposis (FAP)

Question 30

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

Answer 30

turcot syndrome TURcot = TURban (brain tumors)

Question 31

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

Answer 31

Gardner syndrome lumpy vegetables in garden = lumps, bumps all over body

Question 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)

Answer 32

Heriditary nonpolyposis colorectal cancer (HNPCC/Lynch syndrome)

Question 33

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

Answer 33

diverticulosis

Question 34

true diverticula

Answer 34

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

Question 35

false diverticula

Answer 35

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

Question 36

diagnosis

Answer 36

barium enema

Question 37

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

Answer 37

diverticulitis

Question 38

free air in abdomen (below diaphragm) on CT scan

Answer 38

perforated bowel from: appendix PUD diverticulitis

Question 39

treatment of acute flare of diverticulitis

Answer 39

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

Question 40

screening colonoscopy guidelines

Answer 40

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