10 - Large Intestine Flashcards
entamoeba histolytica infection in colon
most often in cecum and ascending colon
cause flask shaped ulcers
amoeba look sorta like macrophages
may penetrate vessels and infiltrate liver > amebic abscess
flask shaped ulcer
entamoeba histolytica in colon
presentation of entamoeba histolytica
abd pain, bloody diarrhea, wt loss
can occasionally lead to acute necrotizing colitis and megacolon
tx for entamoeba histolytica
metronidazole
pseudomembranous colitis - cause and pathogenesis
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
MC abx cause of pseudomembranous colitis
3rd gen cephalosporins
micro path of pseudomembranous colitis
“volcano eruption” of neutrophils and dead cells into lumen
inc chronic inflammatory cells in lamina propria
sx of pseudomembranous colitis
fever, leukocytosis, abd pain/ cramps, hypoalbuminemia, watery diarrhea, dehydration, may have fecal leukocytes or occult blood
tx of pseudomembranous colitis
metronidazole or vanc
2 inflammatory bowel diseases
Crohn disease and ulcerative colitis
difference between Crohn and ulcerative colitis
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
epi of IBD
F > M
common in teens/early 20s
caucasian, ashkenazi jews
pathogenesis of IBD
genetic susceptibility > release of TNF / cytokines in response to stimulus > inc tight jxn permeability > more stimulating material comes in (bacteria stuff) > pos feedback loop
tobacco and IBD
tobacco use inc risk of Crohn, dec risk of ulcerative colitis
Crohn dz micro path
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)
path hallmark of Crohn’s
noncaseating granulomas
extra colonic manifestations of IBD
migratory polyarthritis, sacroiliitis, akylosing spondylitis, uveitis, skin lesions, pericholangitis, primary sclerosing cholangitis
which IBD is assoc w/ colonic dilation / toxic megacolon?
ulcerative colitis
ulcerative colitis micro path
similar to crohn in crypts
no inflammation beyond submucosa really
no granulomas
ulcerative colitis clinical features
relapsing episodes of bloody diarrhea w/ stringy mucoid material, lower abd pain, temporarily relieved by defecation
monitoring for colitis assoc neoplasia
start 8 yrs after dz initiation (unless you have primary sclerosing cholangitis - start right away)
diverticulosis pathophys
low fiber diet > chronic constipation > inc intraluminal pressure > muscular hypertrophy > hernation of mucosa thru muscle wall
where are diverticular most common in colon?
sigmoid
sx of diverticulosis
most asymptomatic
other have intermittent cramping, continuous lower abd discomfort, constipation, distention, sensation of never being able to completely empty rectum
diverticulitis - tx
resolves spontaneously, rare to need surgery
high fiber diet improves sx of diverticulosis
MC neoplastic polyp
adenoma (could become CA)
colonic adenoma = ___ dysplasia
mild
prevalence of adenoma polyps in western world
50% by age 50
surveillance for polyps/colon neoplasia
50 or 10 yr before youngest time of dx for relative
histologic hallmark of colonic adenoma
nuclear hyperchromasia, elongation, and stratification
pedunculated and sessile adenomas - match w/ morphology
pedunculated - tubular adenoma
sessile - villous adenoma
which type of adenoma - tubular or villous - is more likely to invade?
villous
MC malignancy of GI tract
adenoCA of colon
2 distinct genetic pathways for developing colon adenoCA
APC/beta catenin - WNT gene, “classic” adenoCA sequence
microsatellite instability pathway - defects in DNA mismatch repair
gross morphology of colon cancer
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
micro path of colon cancer
invasion w/ strong desmoplastic response
poorly diff cells - few glands
some mucin production > poor prognosis
presentation of colon cancer
proximal: fatigue/weakness due to iron deficiency anemia
distal: occult bleeding, changes in bowel habits, cramping/discomfort in LLQ
colon cancer prognosis
poorly diff and mucinous tumors have poor prognosis
2 important prognostic factors - depth of invasion, LN metastases
where does colon cancer like to metastasize?
regional LNs, lungs, bones, liver
