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Small Intestine - Pseudomembranous Colitis (59)

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Small intestine pathological lesions overview
Incomplete involution of vitelline duct
Meckel's diverticulum
Meckel's diverticulum rules of "2"
2% of normal population

within 2 feet of ileocecal valve

average 2 cm in length
Is Meckel's diverticulum a true or false diverticulum?
true diverticulum: all layers of the GIT are involved.
List 2 types of mucosa that may line Meckel's diverticulum
gastric mucosa: potential for peptic ulcer

pancreatic tissue: somewhat beneficial since the small intestine requires secretions from the pancreas.
Meckel's diverticulum complications
hemorrhage and peptic ulceration (think gastric mucosa)

intestinal obstruction

diverticulitis

perforation

fistula
Review causes of small intestine malabsorption.
Enteropathy triggered by ingestion of gluten-containing diet in a genetically susceptible individual
celiac disease

gluten-sensitive enteropathy

tropical sprue
What protein found in wheat is associated with celiac disease?
gliadin

*antibody used for detection of celiac disease
Is celiac disease more common in whites or blacks?
whites (1 in 300-3000)
Celiac disease age of presentation
1-10 years of age
What part of the intestine is most affected by celiac disease?
proximal part (duodenum)
What causes malabsorption in celiac disease?
marked atrophy and loss of villi --> reduction of area for absorption
What immune cells in the epithelial cells cause celiac disease?
T lymphocytes

*diagnostic
What happens to the crypts of the small intestine in celiac disease?
elongate and undergo hyperplasia
List 3 immune cells found in the lamina propria of a patient with celiac disease.
lymphocytes

macrophages

plasma cells
What congenital disorder is associated with celiac disease?
Down syndrome
Celiac disease pathogenesis
What antigen is expressed in most patients with celiac disease?
MHC class 2

*specifically HLA DQ2

*occasionally HLA DQ8
What is the most common serological test for celiac disease?
anti-tissue transglutaminase

*associated with IgA
Celiac disease Dx
What type of cancer is associated with celiac disease?
intestinal lymphomas (T cell type)
What skin condition is associated with celiac disease?
dermatitis herpetiformis: an extremely itchy chronic rash made of bumps and blisters.
Tropical sprue pathogenesis
bacterial infection superimposed on a pre-existing small intestine injury

*history of traveling to the tropics
What part of the small intestine is affected by tropical sprue?
all parts of the small intestine are involved equally
List the 3 main parts of the body affected by Whipple's disease
intestine (mainly duodenum)

joints

CNS
Whipple's disease pathogenesis
gram-positive sickle-shaped actinomycete Trepophyrema whippelii causes the mucosa to build up with foamy macrophages in the lamina propria
Whipple's disease sex
males (10:1)
What is the most common cause of congenital intestinal obstruction?
Hirschsprung's disease
Hirschsprung's disease sex
males (4:1)
What congenital disorder is associated with Hirschsrpung's disease?
Down syndrome
Hirschsprung's disease pathogenesis
The absence of ganglion cells in Meissner's and Auerbach's plexuses causes dilatation and hypertrophy proximal to the aganglionic segment due to the functional obstruction (no peristalsis).
What causes the absence of ganglion cells in Hirschsprung's disease?
defect in migration and survival of neuroblasts
List 3 clinical features of Hirschsprung's disease.
delayed passage of meconium

constipation

abdominal distension
Hirschsprung's disease Dx
rectal biopsy
Hirscprung's disease complications (2)
enterocolitis

perforation leading to peritonitis
Diverticular disease pathogenesis
lack of dietary fiber leads to sustained bowel contractions and increased intraluminal pressure
Diverticulitis Sx (3)
lower abdomen pain

constipation

diarrhea

flatulence

fever
Diverticulitis complication
perforation
Colitis (general) Sx
diarrhea (mucoid or bloody)

abdominal pain (usually below umbilicus)

abdominal cramps

tenesmus: painful defecation
Colitis (general) etiology
Pseudomembranous colitis pathogen
Clostridium dificile
Pseudomembranous colitis pathogenesis
Broad spectrum antibiotic use allows for a normally commensal organism to overgrow and cause TOXIN-mediated damage. The surface epithelium is denuded and mucopurulent exudate erupts to form mushrooming clouds. Coalescence of these clouds leads to the formation of the pseudomembrane.
What part of the colon is most commonly affected by pseudomembranous colitis?
rectosigmoid colon