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

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