large intestine Flashcards
failure of neural crest cell migration dysfunctional Auerbach (muscularis externa layer) + Meissner plexus (submucosal layer) → abnormal peristaltic waves
Hirschsprung disease
congenital megacolon with meconium ileus or if less severe, chronic constipation as infant (chronic distention)
Hirschsprung disease
twisting of colon around mesentary → ischemia
volvulus
most common location of volvulus in elderly (most commonly affected by volvulus)
cecum or sigmoid colon
most abundant bacterial flora in large intestine
#1 bacteroides fragilis #2 E. coli (enterobacteraciae) other enterobacteraciae: proteus mirabilis proteus vulgaris salmonella shigella klebsiella pneumoniae
complication of obstruction of appendicitis with:
adults: fecalith (fecal stone)
kids: viral infection (hyperplasia of lymphoid tissue= MALT tissue)
appendicitis
N/V
diffuse periumbilical pain → later, pain localizes to RLQ (McBurney’s point)
rebound tenderness in RLQ
leukocytosis on CBC
appendicitis
McBurney’s point
2/3 the way from umbilicus to ASIS
confirm diagnosis of appendicitis
r/o ectopic pregnancy with female (serum bHCG)
adults: CT scan
kids or pregnant: US
line anus that marks end of endoderm and beginning of ectoderm (squamous cell)
pectinate line
pathology proximal to pectinate line
internal hemorrhoids: not painful, may bleed
tx: can band → necrosis
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)
cancer above pectinate line is most likely
adenocarcinoma (rectal)
pathology distal to pectinate line
external hemorrhoids: very painful
tx: numbing agent -symptomatic relief
cancer below pectinate line is most likely
squamous cell carcinoma (anus)
biggest risk factor for squamous cell carcinoma of anus
HPV 16, 18, 31
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
most common type of polyp in colon - found in rectum or rectosigmoid
hyperplastic polyp
polyp with no precancerous risk (benign)
removed during colonoscopy since need bx to prove not cancerous
hyperplastic polyp
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)
child
juvenile polyps
if one: no malignant potential
if many: juvenile polyposis syndrome →↑ risk adenocarcinoma
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
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
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
incidental finding of anemia in >50 yo
screen for colon cancer (GI bleed - most commonly R. sided cancer)
diagnosis of colon cancer
colonoscopy: >50 yo fecal occult blood testing barium enema flexible sigmoidoscopy confirmation: tissue bx
“apple-core” lesion with barium enema
narrowing of lumen of colon
suggest colon cancer
CEA is a tumor marker for
colon cancer
nonspecific: but useful for monitoring for recurrence after treatment for colon cancer
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)
FAP (mutation of APC gene, 1000s of polyps) + malignant CNS tumors (medulloblastoma)
turcot syndrome
TURcot = TURban (brain tumors)
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
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)
> 60 yo with many blind pouches in sigmoid colon
usually asymptomatic or
vague pain in LLQ RELIEVED with defecation or
painless rectal bleeding
diverticulosis
true diverticula
outpouching of all three layers of gut wall
example: meckel diverticulum
false diverticula
outpouching of only mucosa + submucosa due to weak spots in muscularis externa (where vasa recta perforate muscularis externa)
example: colonic diverticulum
diagnosis
barium enema
LLQ pain (sigmoid colon) fever elevated WBC count rectal bleeding constipation due to inflammation in colon peritonitis (if perforation)
diverticulitis
free air in abdomen (below diaphragm) on CT scan
perforated bowel from:
appendix
PUD
diverticulitis
treatment of acute flare of diverticulitis
antibiotics: metronidazole (anaerobic bacteria) + TMP-SMX or FQ (ciprofloxacin)
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
