ALU 301 - Ch 2 - Inflammatory Bowel Disease (2024)
inflammatory bowel disease (IBD)
Term used for 2 inflammatory conditions of undetermined etiology.
1. Ulcerative Colitis (UC)
2. Crohn's Disease (CD)
--Generally accepted idea that UC and CD are diff dz's but have overlapping manifestations ...
ALU 301 - Ch 2 - Inflammatory Bowel Disease (2024)
inflammatory bowel disease (IBD)
Term used for 2 inflammatory conditions of undetermined etiology.
1. Ulcerative Colitis (UC)
2. Crohn's Disease (CD)
--Generally accepted idea that UC and CD are diff dz's but have overlapping manifestations making it
difficult to distinguish one from the other
--Both manifest as dz's of GI tract characterized by chronic inflammation w intermittent periods of
exacerbation and remission. Both can be assoc w dz outside the intestinal tract.
Normal Immune Response
is well regulated and turns itself off when it has performed job of defending the body from harm.
Etiology of IBD - Part 1
-Remains unknown
Several proposed explanations include:
1. genetic susceptibility - familial link; no genetic marker.
>Risk of dz is 14-15x higher than the general population. High degree of concordance in identical
twins. Relatives of CD have 10x the risk/Relatives of UC 8x the risk.
>There can be multiple genes involved in the dz development.
Etiology of IBD - Part II
2. environmental factors -
>use of NSAIDs can alter intestinal barrier & cause exacerbation of the dz.
>Appendectomy is protective if had the sgy at an early age.
> Smoking may modify phenotype w varying effects. Protective against UC, but ^ the risk in CD /can
make it worse
>Intestinal bacteria (Luminal flora) or their antigen products may be a factor -therefore infections &
Abx that alter gut flora are possible risk factors
>Diet is a risk factor: Foods high in fat/sugar can trigger immune response, resulting in developing of
IBD
Etiology of IBD - Part III
3. Abn of the mucosal immune system - In IBD (& other inflamm & Autoimmune Dz's) the immune
response becomes self-sustaining & unregulated. It is not clear why this happens --could be b/c of
intrinsic defect or damage to epithelial barrier.
ALL 3 proposed etiologies are responsible for the clinical dz
No one single factor alone is causal.
, The prevalence & incidence of IBD vary widely and depend on several factors:
1. Age >onset age of most cases btwn 15 and 40yrs
------------------------------------------------
2. Ethnic background
> primarily white people. Amer Jews of Euro descent 4-5x more likely. In U.S. racial & ethnic diff seem
to be narrowing.
-------------------------------------------------
3. geographic location
>More common in Urban area, and in Northern climates. North to south incidence nearly same in
Canada /USA as in Europe. When pop. move from a developing country to a developed one, the dz
freq increases
>Affected w IBD in US - approx 1.6mil / Affected with IBD in Europe 2.2mil.
--------------------------------------------------
4. "Western Lifestyle" in developed countries (Sedentary lifestyle, high fat/simple carb diet. However,
beginning to increase in Japan and Korea
**differences in incidence across age, time, smoking hx, geo location seem to suggest environmental
factors contribute to UC/CD
**No difference in rates for males/females, but slight preponderance of UC in males and Crohns in
females
Ulcerative Colitis - Areas of involvement
ONLY in the Colon, and only in the mucosa (inner lining of the gut). DOES NOT involve whole wall of
colon. Inflammatory process begins in the rectum & advances proximally in a confluent & continuous
pattern.
>rectum or rectosigmoid area is affected in only 30% of cases (Ulcerative proctitis or
proctosigmoiditis)
>40% of case only affect the sigmoid and descending colon (L sided colitis)
> remaining 30% the entire colon is affected (pancolitis or proximal to the splenic flexure)
Ulcerative Colitis - Symptoms
--Rectal Bleeding --most common (typically bloody diarrhea)
--Abdominal Cramping
--Constant Fecal Urgency
--Passage of mucopurulent discharge
**Pattern of severity usually est. early. 1st 5yrs will give you an ideal of how the dz will progress.
Evidence to suggest if not progressed to the splenic flexure in 2yrs, it willl prob not progress further
Ulcerative Colitis - Older Population
--30% of new cases are dx in ages over 60
--More Males than females are dx in this age group, and it more often confined to L Colon
--Sx's at onset in this age group are more severe, but once controlled w tx, can have a more benign
course w little increase in mortality
Ulcerative Colitis - Dz Severity
Determined by Clinical Sx's and Endoscopy
Intestinal mucosa:
>is friable (bleeds easily)
>hyperemic (more blood vessels than NML)
>multiple mucosal ulcerations
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