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