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What are the four pathophysiologic mechanisms of diarhhea?
Osmotic, secretory, inflammatory, malabsorptive.
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What characterizes acute diarrhea, persistent, chronic?
- acute: < 14 days
- persistent: > 14 days
- chronic: > 30 days
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How does small bowel diarrhea present?
- Large volume watery stool
- mid abdominal pain.
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How does colon ("dysenteric") diarrhea present?
- Small volume stool with blood and tenesmus
- lower abdominal pain
- red cells and leukocytes in the stool.
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Name 7 bacteria that preferentially affect the small bowel?
Salmonella, E. coli, Staph aureus, C. perfringens, B. Cereus, V. cholerae, Aeromonas hydrophila.
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Name two viruses that affect the small bowel preferentially?
Rotovirus, Norovirus.
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Name 6 bacteria that preferentially affect the colon?
Campylobacter, Shigella, Yersinia, Enteroinvasive E. coli, C. difficile, Vibrio parahaemolyticus.
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Name three viruses that affect the colon preferentially?
CMV, Adenovirus, Herpes simplex.
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What is the only protozoa that affects the colon preferentially?
Entamoeba histolytica.
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What is the leading cause of foodborne illness in the US?
Non typhoid salmonella.
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Who is at higher risk for E. Histolytica infection and diarrhea?
- Institutionalized patients, homosexuals
- Found mostly in migrants and travelers.
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What is the pathogenesis of Cholera diarrhea?
Cholera toxin activates adenylate cyclase, increasing cAMP -> activated Cl channel -> increased Cl secretion and decreased Na absorption -> more ions in lumen -> more water in lumen -> voluminous diarrhea.
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What is in the DDx with acute bloody diarrhea?
- E. Coli 0157:H7
- Shiguella
- Campylobacter
- Some salmonella species
- Non-infectious causes: UC, Crohns, ischemic colitis.
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What is in the DDx with fecal leukocytes?
- Shigellosis
- Enteroinvasive E. coli
- V. Parahemolyticus
- C. dificcile
- Ulcerative colitis
- Ischemic colitis
- Salmonella enteritidis.
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What organisms preform toxins?
B. cereus, C. perfringens, Staph aureus.
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What organisms produce enterotoxins?
Aeromonas species, V. Cholerae, enterotoxigenic E. coli.
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What organisms produce cytotoxins?
C. difficile, E. coli 0157:H7.
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What organisms produce diarrhea through enteroadherence mechanisms?
Cryptosporidiosis (cryptosporidium parvum), Cyclospora species, enteroadgerent and enteropathogenic E. coli, Helminths, Giardia Lamblia.
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What organisms cause severe mucosal invasion (invade severely)?
Entamoeba Histolytica, Shigella species, Enteroinvasive E. Coli.
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Where do you see penetrating enteric invasion?
- Distal small bowel
- fecal mononuclear leukocytes
- Enteric fever syndrome.
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Where do you see non-inflammatory enteric infection?
- Proximal small bowel
- water diarrhea
- no fecal leukocytes.
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Where do you see inflammatory enteric infection?
- Colon
- dysentery
- fecal polymorphonuclear leukocytes.
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What is enteric fever?
- Systemic febrile illness originating from distal small bowel
- Exhibiting some combination of: sustained fever, headache, rash, splenomegaly, fecal mononuclear leukocytes, positive blood culturees.
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What are three organisms that may cause enteric fever?
Salmonella typhi, Yersinia enterocolitica, campylobacter fetus.
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Name three poorly absorbable CHOs, what do they cause?
- Lactulose, sorbitol, fructose
- Osmotic diarrhea - is relieved by fasting.
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What causes seretory diarrhea?
- Net secretion of anions (Cl-, bicarbonate)
- Persists during fasting.
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What are two syndromes causing secretory diarrhea, by what mechanisms?
- Zollinger-Ellison syndrome: excess secretion of gastrin
- Pancreatic Cholera syndrome: Excess production of VIP.
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What are three mechanisms of diarrhea with IBDs?
- Exudative caused by mucosal destruction
- Secretory due to cytokines and bacterial toxins
- Malabsorptive from mucosal surface damage.
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What does exudative diarrhea stool contain?
Mucus, serum protein, blood, cellular debris.
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What are three causes of exudative diarrhea?
IBD, Ischemic bowel disease, Bacillary dysentery (shigellosis).
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What is used to diagnose the cause of chronic inflammatory diarrhea?
Radiographs and endoscopy.
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What stain is use to visualize fat droplets in stool?
Sudan stain.
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What are some causes of fatty diarrhea?
- Malabsorption syndrome: Whipple's disease, short bowel syndrome, celiac sprue, bacterial overgrowth
- Maldigestion syndrome: Pancreatic exocrine insufficiency, reduced bile acid pool (ileal resection).
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What are some complications of Celiac Sprue?
- Vitamin Deficiency: Fat soluble and non-fat soluble (folate)
- Iron deficiency
- Osteoporosis.
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How do bile acids affect colonic secretions?
Increase colonic secretions of water and electrolytes.
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