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Flashcards in Gastro 3 Deck (25)
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1

painful, bloody, small-volume diarrhea

Dysentery

2

isotonic stool (intestinal fluid secretion is isotonic with plasma) during fasting

Secretory diarrhea

3

concentrated stool, unabsorbed luminal solutes while fasting

Osmotic diarrhea

4

resulting from inflammatory disease, purulent, bloody stools even when fasting

Exudative diarrhea

5

inadequate nutrient absorption with steatorrhea (fat), relieved when fasting

Malabsorptive diarrhea
-Arises from disturbances of intraluminal digestion, terminal digestion (in brush border), transepithelial transport or lymphatic transport
-Despite varying causes, malabsorptive disorders are similar in presentation
-Diarrhea, flatus, abdominal pain, weight loss (anemia)
-Celiac disease, cystic fibrosis, lactose deficiency, environmental enteropathy (stunted growth related to impaired intestinal function)

6

most common symptom of intestinal disease

Diarrhea

7

Celiac Disease

Arises from dietary gluten sensitivity
Classically appears 6-24 months of age with irritability, abdominal distention, anorexia, diarrhea, weight loss
Serologic tests indicate IgA antibodies to gliadin4+ T cells creating inflammatory reaction & tissue damage as well as IL-15-mediated expansion of CD8+ T cells
Deaminated gliadin is presented to CD4+ T cells
Pts at risk for T cell lymphoma and small intestinal adenocarcinoma

8

Lactase deficiency (Lactose intolerance)

Results from deficiencies of disaccaharidases located in brush border
Congenital lactase deficiency is autosomal recessive mutation in lactase gene
Acquired lactase deficiency due to downregulation of lactase gene expression (adults)
Pts present with explosive diarrhea, abdominal distention after milk ingestion
Treated with removal of lactose from diet

9

Abetalipoproteinemia

Pts present in childhood with diarrhea, steatorrhea, failure to thrive
Autosomal recessive disease with inability to secrete triglyceride-rich lipoproteins from GI epithelium
Accumulation of mono & triglycerides in epithelial cells
Defect in transepithelial transport

10

Microscopic colitis

Pts present with chronic, non-bloody watery diarrhea, without weight loss

11

Intestinal graft-versus-host

Presents with watery diarrhea due to donor T-cells targeting recipient’s intestinal epithelium

12

Diarrheal disease: Infectious enterocolitis

Caused by bacterial, viral or parasitic infections responsible for ½ worldwide deaths by 5 yrs

13

Cholera (Vibrio cholerae)

Transmitted though contaminated food/water (poor sanitation)
Seasonal incidence during warm weather
Non-invasive, remains in the intestinal lumen
Cholera toxin that stimulates adenylate cyclase to increase cAMP which open CF receptors resulting in increased luminal chloride causing secretory diarrhea
Watery diarrhea (1L/hr) after 1-5 day bacterial incubation
Typically results in massive fluid loss leading to shock

14

Shigellosis (Shigella)

Shigella is minimally invasive that produces bloody, watery diarrhea after 1-7 days incubation
Shigella is resistant to acidic stomach environment so small dose is highly infective
Self-limiting disease that can benefit from anti-biotics, but anti-diarrheal drugs delay bacterial clearance

15

Typhoid fever (Salmonella typhi)

Transmitted though contaminated food/water (poor sanitation)
Invasive pathogen involves the full thickness of the intestinal wall, can produce septicemia.
Presents with acute vomiting, bloody diarrhea, abdominal pain followed by flu-like phase and lastly a high fever phase
Seasonal incidence during warm weather

16

Infectious enterocolitis: Pseudomembranous Colitis

-Killing of commensal bacteria by antibiotics allows the expansion of resistant
microorganisms that can cause disease
-Clostridium difficile colonizes many hospitals and nursing homes, and antibiotic treatment can allow it to proliferate in the intestinal tract
-Toxin produced by C. difficile causes pseudomembranous colitis with mucosal necrosis and severe bloody diarrhea characterized by a gray-green exudate adherent to the mucosal surface

17

Norovirus

Transmitted though contaminated food/water (poor sanitation) as well as person-to-person
‘Cruise-ship’ disease, very common
Presents with nausea, vomiting, watery diarrhea and abdominal pain
Self-limiting disease

18

Rotavirus

Most common cause of severe childhood diarrhea and diarrhea-mediated deaths world-wide
Ages 6 months – 2 years
Infects and destroys mature adsorptive enterocytes
Villus surface epithelial cells are replaced with immature & ineffective adsorptive cells resulting in osmotic diarrhea

19

Giardia lamblia

Intestines can harbor parasites & protozoa
Giardia is a flagellated protozoan is most common parasitic infection in humans
Cysts are transmitted though contaminated food/water (poor sanitation)
Non-invasive trophozoites are released from cysts in stomach
Giardia evades immune surveillance by modulating surface antigens
Giardia reduces brush border enzymes, damages small intestinal epithelial cells
Parasites can cause diarrhea, malabsorption, and GI hemorrhage

20

Inflammatory Bowel Disease

-Females > males, adolescence or young adults
-Two forms are distinguished: Crohn's disease and ulcerative colitis
-affects the large (&small) intestine

21

ulcerative colitis

UC occurs in colon & rectum
UC extends only into mucosa & submucosa

22

Crohn's disease

Crohn’s occurs throughout small & large intestine
Crohn’s is usually transmural, skip lesions present

23

IBD: aberrant immune response

Arises from inappropriate immune reaction
Hygiene hypothesis
NOD2 as gene risk for Crohn’s
Altered TH1 & TH17 cell response in Crohn’s
Abnormal Paneth cell granules in Crohn’s disease

24

Collagenous colitis:

middle aged women
presence of dense subepithelial collagen layer, increased intraepithelial lymphocytes and mixed inflammatory infiltrate within the lamina propria

25

Lymphocytic colitis:

subepithelial layer is not thickened, excessive intraepithelial lymphocytes
Often associated with celiac and other autoimmune diseases