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What are the four pathophysiologic mechanisms of diarhhea?
Osmotic, secretory, inflammatory, malabsorptive.
What characterizes acute diarrhea, persistent, chronic?
- acute: < 14 days
- persistent: > 14 days
- chronic: > 30 days
How does small bowel diarrhea present?
- Large volume watery stool
- mid abdominal pain.
How does colon ("dysenteric") diarrhea present?
- Small volume stool with blood and tenesmus
- lower abdominal pain
- red cells and leukocytes in the stool.
Name 7 bacteria that preferentially affect the small bowel?
Salmonella, E. coli, Staph aureus, C. perfringens, B. Cereus, V. cholerae, Aeromonas hydrophila.
Name two viruses that affect the small bowel preferentially?
Name 6 bacteria that preferentially affect the colon?
Campylobacter, Shigella, Yersinia, Enteroinvasive E. coli, C. difficile, Vibrio parahaemolyticus.
Name three viruses that affect the colon preferentially?
CMV, Adenovirus, Herpes simplex.
What is the only protozoa that affects the colon preferentially?
What is the leading cause of foodborne illness in the US?
Non typhoid salmonella.
Who is at higher risk for E. Histolytica infection and diarrhea?
- Institutionalized patients, homosexuals
- Found mostly in migrants and travelers.
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.
What is in the DDx with acute bloody diarrhea?
- E. Coli 0157:H7
- Some salmonella species
- Non-infectious causes: UC, Crohns, ischemic colitis.
What is in the DDx with fecal leukocytes?
- Enteroinvasive E. coli
- V. Parahemolyticus
- C. dificcile
- Ulcerative colitis
- Ischemic colitis
- Salmonella enteritidis.
What organisms preform toxins?
B. cereus, C. perfringens, Staph aureus.
What organisms produce enterotoxins?
Aeromonas species, V. Cholerae, enterotoxigenic E. coli.
What organisms produce cytotoxins?
C. difficile, E. coli 0157:H7.
What organisms produce diarrhea through enteroadherence mechanisms?
Cryptosporidiosis (cryptosporidium parvum), Cyclospora species, enteroadgerent and enteropathogenic E. coli, Helminths, Giardia Lamblia.
What organisms cause severe mucosal invasion (invade severely)?
Entamoeba Histolytica, Shigella species, Enteroinvasive E. Coli.
Where do you see penetrating enteric invasion?
- Distal small bowel
- fecal mononuclear leukocytes
- Enteric fever syndrome.
Where do you see non-inflammatory enteric infection?
- Proximal small bowel
- water diarrhea
- no fecal leukocytes.
Where do you see inflammatory enteric infection?
- fecal polymorphonuclear leukocytes.
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.
What are three organisms that may cause enteric fever?
Salmonella typhi, Yersinia enterocolitica, campylobacter fetus.
Name three poorly absorbable CHOs, what do they cause?
- Lactulose, sorbitol, fructose
- Osmotic diarrhea - is relieved by fasting.
What causes seretory diarrhea?
- Net secretion of anions (Cl-, bicarbonate)
- Persists during fasting.
What are two syndromes causing secretory diarrhea, by what mechanisms?
- Zollinger-Ellison syndrome: excess secretion of gastrin
- Pancreatic Cholera syndrome: Excess production of VIP.
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.
What does exudative diarrhea stool contain?
Mucus, serum protein, blood, cellular debris.
What are three causes of exudative diarrhea?
IBD, Ischemic bowel disease, Bacillary dysentery (shigellosis).
What is used to diagnose the cause of chronic inflammatory diarrhea?
Radiographs and endoscopy.
What stain is use to visualize fat droplets in stool?
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).
What are some complications of Celiac Sprue?
- Vitamin Deficiency: Fat soluble and non-fat soluble (folate)
- Iron deficiency
How do bile acids affect colonic secretions?
Increase colonic secretions of water and electrolytes.