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IBD path
GI
46
Medical
Graduate
08/31/2010

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Term
what is inflammatory bowel disease (IBD)?
Definition
chronic inappropriate mucosal immune activation and depending on distribution of the lesions and mucosal alterations it is classified as either crohn disease or ulcerative colitis
Term
which has a greater risk of adenocarcinoma formation, chrons or ulcerative colitis?
Definition
ulcerative colitis
Term
what characterizes crohn's disease?
Definition
crohn's is a systemic disorder which can affect anywhere from the alimentary tract to the anus and tends to involve *skip lesions*. with crohn's there is a higher likelihood of *transmural inflammation (involving entire bowel wall thickness) - leading to more ulcerations, fissures, and fistulas
Term
are colectomies performed in crohn's disease? what about ulcerative colitis?
Definition
crohn's: no b/c it's not just limited to the colon. ulcerative colitis: yes, b/c there is continous involvement of the colon.
Term
what characterizes ulcerative colitis?
Definition
UC only involves the colon, beginning distally from the rectum, continuously moving proximally. it can be diagnosed with a sigmoidoscopy and pts are likely to have ulcers and *pseudopolyps (reparative mechanisms)
Term
what is the etiology of IBD?
Definition
idiopathic, most likely a result of defects in host interactions w/intestinal microbiota, intestinal epithelial dysfunction and aberrant mucosal immune responses
Term
if a pts other family members have IBD, is the risk higher
Definition
yes
Term
what gene is thought to be specifically associated with the inflammatory component of IBD?
Definition
the *NOD2 gene (nucleotide oligomerization binding domain 2) which encodes a protein that binds to intracellular bacterial peptidoglycans and activates NF-kB may be mutated, leading to less effective recognition of/combating luminal microbes which ultimately leads to inflammation. (NOD2 may regulate immune responses to prevent excessive activation by luminal microbes)
Term
what is role of the ATG16L1 (autophagy-related 16-like) gene in IBD?
Definition
this gene is critical to host responses to intracellular bacteria (if mutated, problems occur)
Term
what is role of the IRGM (immunity-related GTPase M) gene in IBD?
Definition
this gene is involved in autophagy and clearance of intracellular bacteria (if mutated, problems occur)
Term
what characterizes the mucosal immune response in IBD?
Definition
T cells polarize to Th1 type (Th17 also participate) and alter immune responses, leading to increased inflammation w/release of TNF and various ILs
Term
what is the progression of IBD in terms of bacterial/T cell involvement?
Definition
bacteria elaborate through the epithelial cells, macrophages release TNF (can further injure cells), Th1/Th17 are activated (release ILs which can injure cells), neutrophils are activated, and an acute inflammatory response is activated
Term
what are the 3 kinds of epithelial defect common to IBD?
Definition
epithelial barrier defects (doesn't protect itself from bacteria well), defective transepithelial transport (unable to transport nutrients - malabsorbtion), and paneth cell granules which contain antibacterial peptides are abnormal in crohn's disease. (all problems of inadequate protection from normal flora)
Term
why might antibx be helpful in IBD?
Definition
there is much evidence that intestinal microbiota contribute to IBD as *antibodies formed against the bacterial protein flagellin* is associated with strictures, perforation and small bowel involvement in crohn's disease
Term
where are the most common sites for crohn disease to affect?
Definition
the terminal ileum, ileocecal valve and the cecum - though it can occur at any level of the GI tract.
Term
are strictures common in crohn disease?
Definition
yes - which can contribute to bowel obstruction
Term
what does it mean that crohn disease has "skip lesions"?
Definition
areas of involved bowel are interspersed with uninvolved bowel
Term
what characterizes an early crohn disease lesion?
Definition
aphthous ulcers which progress, producing multiple serpentine linear ulcers along the long axis
Term
how can you dx chron disease?
Definition
barium enema, colonscopy and bx
Term
what is the "cobblestone appearance" attributed to crohn disease?
Definition
due to sparing of mucosa and patchy distribution of crohn disease a level of depressed diseased tissue results below the level of normal mucosa
Term
how do fissures form in crohn disease?
Definition
these occur between mucosal folds, and if deep enough - can cause fistulae or perforation
Term
what kind of IBD has transmural involvement?
Definition
crohn disease; and it is characterized by thickened walls, edema, submucosal fibrosis, and hypertrophy of the muscularis propria - which can all contribute to stricture formation
Term
what is the "creeping fat" seen in crohn disease?
Definition
mesenteric fat extending around the serosal surface which occurs as a protective mechanism
Term
what are the crypt abscesses found in crohn disease?
Definition
crypt abscesses are due to abundant neutrophils infiltrating the crypt epithelium (may destroy the crypt). this can lead to haphazard crypt organization due to repeated bouts of damage and regeneration.
Term
what are some other histologic features of crohn disease?
Definition
*paneth cell metaplasia in the L colon, *pseudopyloric metaplasia, *mucosal atrophy (leads to malabsorption), and *non-caseating granulomas found in any layer of the intestinal wall (almost never seen in ulcerative colitis - very important feature)
Term
what are the clinical features of crohn disease?
Definition
variable. diarrhea (rarely bloody), fever, abdominal pain, possible abdominal mass, malabsorption commonly
Term
what can crohn disease mimic?
Definition
appendicitis or bowel perforation
Term
can crohn disease have asymptomatic periods?
Definition
yes, and stress, smoking, and diet may initiate relapses
Term
what kind of CA does crohn disease increase risk for?
Definition
adenocarcinoma - but risk is not as high as in pts w/ulcerative colitis
Term
what extraintestinal manifestations are associated with crohn disease?
Definition
uveitis (eye irritation), migratory polyarthritis, sacroiliitis, ankylosing spondylitis, erythema nodosum, pericholangitis, and primary sclerosing cholangitis
Term
what areas of the body are affected by ulcerative colitis?
Definition
ulcerative colitis involves the rectum and extends proximally into the colon in a continuous fashion *w/o skip lesions. sometimes you may have a little involvement of the ileum, which is called: *backwash ileitis
Term
how do the extraintestinal manifestations associated with ulcerative colitis compare to crohns disease?
Definition
they are similar, but ulcerative colitis has a higher incidence of extraintestinal manifestations including: uveitis (eye irritation), migratory polyarthritis, sacroiliitis, ankylosing spondylitis, erythema nodosum, pericholangitis, and primary sclerosing cholangitis
Term
which has a higher incidence of adenocarcinoma, crohn disease or ulcerative colitis?
Definition
ulcerative colitis
Term
which disease has a higher overall incidence, crohn disease or ulcerative colitis?
Definition
ulcerative colitis
Term
what is the prognosis for ulcerative colitis?
Definition
it depends on the severity and duration
Term
what is pancolitis?
Definition
the entire colon is affected by ulcerative colitis
Term
what is left-sided colitis?
Definition
colonic involvement does not extend beyond the transverse colon
Term
how does the surface of a colon affected by ulcerative colitis appear?
Definition
the colonic mucosa is red, granular, and may have broad-based ulcers (aligned along the long axis). *pseudopolyps, which are islands of regenerating mucosa extend into the lumen and may resemble neoplastic polyps. the tips of these pseudopolyps may fuse, forming *mucosal bridges. there may be an abrupt transition between diseased and normal colon.
Term
how does colon affected by ulcerative colitis appear histologically?
Definition
there may be *mucosal atrophy though mural thickening is absent, and the serosal surface is normal (no creeping fat/fissures)
Term
do strictures occur with ulcerative colitis?
Definition
no
Term
what is a toxic megacolon?
Definition
this is due to damage to the muscularis propria and neuromuscular functioning of the colon - the bowel continually dilates
Term
does ulcerative colitis present as a mass?
Definition
not usually
Term
is bloody diarrhea common with ulcerative colitis?
Definition
yes
Term
how does ulcerative colitis compare to crohn's disease?
Definition
pretty similar - the same crypt abscesses, crypt distortion and epithelial metaplasia occurs - but generally there are *no granulomas* in ulcerative colitis
Term
what are clinical symptoms of ulcerative colitis?
Definition
attacks of bloody diarrhea with stringy mucoid material and abdominal pain and cramps which may last for days to months
Term
what is the treatment for ulcerative colitis?
Definition
colectomy cures colitis, but extraintestinal manifestations linger
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