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)
Enteropathy triggered by ingestion of gluten-containing diet in a genetically susceptible individual
What protein found in wheat is associated with celiac disease?
*antibody used for detection of celiac disease
What causes malabsorption in celiac disease?
marked atrophy and loss of villi --> reduction of area for absorption
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.
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?
*associated with IgA
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)
Whipple's disease pathogenesis
gram-positive sickle-shaped actinomycete Trepophyrema whippelii causes the mucosa to build up with foamy macrophages in the lamina propria
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
Diverticular disease pathogenesis
lack of dietary fiber leads to sustained bowel contractions and increased intraluminal pressure
Colitis (general) Sx
diarrhea (mucoid or bloody)
abdominal pain (usually below umbilicus)
tenesmus: painful defecation
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.