this lecture is a continuation of the diagnosis of GI disorders by Dr. Thom, focusing on gastroenteritis. first topic: diarrhea. there are in general four mechanisms for causing diarrhea. it can be caused osmotically by the presence of large amounts of undigestable solutes as in lactose intolerance or laxatives. secondly, it can be caused by secretion of ions from the enterocytes into the intestinal lumen, from enterotoxins, or hormones, or laxatives. thirdly, it can be an inflammatory or infectious process accompanied by blood, mucous, or protein exudate. lastly, diarrhea can be caused by excessively increased or decreased contact between the mucosa and GI contents. patients with diarrhea caused by a microorganism are likely to show any of these symptoms: dehydration, failure to thrive/malnutrition, abdominal pain not worsened with palpation, borborygmi, and perianal erythema.
gastroenteritis can be virally or bacterially caused. the viruses most commonly associated with gastroenteritis are rotavirus (which causes the most cases of infectious diarrhea worldwide), adenovirus, norwalk virus, calci virus, astrovirus. bacterial gastroenteritis can be caused toxigenically due to a preformed toxin that is then ingested, or from toxins formed in the intestine, or from invasion of the intestine by the microorganism itself. of the toxigenic bacteria, staph aureus is most commonly implicated in cases of bacterial gastroenteritis. food poisoning from food that was left out in room temperature or in picnics is generally due to staph aureus and resolves quickly, sometimes within a few hours. bacillus cereus poisoning is associated with chinese food and results in emesis followed by diarrhea. cholera produces copious watery diarrhea 1-3 days after infection. clostridium perfringens is associated with meat products and clostridium botulinum is associated with home canned foods and freshwater fish.
gastroenteritis can also be caused by "enteroinvasive" bacteria such as campylobacter jejuni, shigella, salmonella, and e.coli, and can result in watery and/or bloody diarrhea. c. jejuni causes the most cases of bloody diarrhea in the US and starts with a prodrome with vague systemic symptoms, followed by watery diarrhea, followed by bloody diarrhea. it is associated with contaminated meat and dairy products and might have an incubation of 1-7 days. salmonella is associated with meat and dairy as well, in particular raw unpasteurized milk. shigella is most common in young children, is highly contagious, and might have an incubation period of 1-3 days. gastroenteritis due to e.coli is of two types: enteropathogenic, associated with nurseries and watery diarrhea, and enterohemorrhagic, associated with undercooked beef and bloody diarrhea. e.coli might be difficult to treat because antibody treatment might simply release toxins from inside the e. coli cells and increase toxin exposure.
gastroenteritis can also be caused by parasite infection: three such parasites are giardia lamblia, cryptosporidium, and entameoba histolytica. giardia and entameoba are both fecal oral, travel related, and occur due to ingestion of cysts, while cryptosporidium is nearly ubiquitous in water supplies. giardia has a 1-2 week incubation, followed by a mild self limiting enteritis with watery diarrhea, bloating, and flatulence. cryptosporidium is characterized by profuse watery diarrhea and low grade fever, and entameoba histolytica can produce cramps, abdominal pain, fever, and bloody diarrhea.
questions
diarrhea...
1. what are the four major mechanisms for the pathophysiology of diarrhea?
2. what is the osmotic mechanism for diarrhea?
3. what is the secretory mechanism for diarrhea? what is it caused by?
4. what is the exudative mechanism for diarrhea?
5. what is the "motility" mechanism for diarrhea?
6. what are 5 PE findings for patients with diarrhea caused by a microorganism?
gastroenteritis...
7. what are the viruses most commonly associated with gastroenteritis?
8. rotavirus is the most common cause of...
9. when during the year is the peak incidence of gastroenteritis caused by rotavirus?
10. what are the three mechanisms for pathogenesis of bacterial gastroenteritis?
11. what are the "toxigenic" bacteria associated with bacterial gastroenteritis?
12. what is the most common cause of s. aureus food poisoning and how serious is it?
13. bacillus cereus is associated with what type of food?
14. what are the 2 distinct symptoms associated with bacillus cereus food poisoning?
15. how long after ingestion does cholera produce diarrhea?
16. what is the WHO rehydration formula composed of?
17. what foods are clostridium perfringens associated with?
18. how many different types of toxins are produced by clostridium perfringens and botulinum?
19. clostridium botulinum food poisoning from toxins A,B is associated with...
20. clostridium botulinum food poisoning from toxins E is associated with...
21. clostridium botulinum can cause...
22. what is the incubation period for clostridium botulinum?
gastroenteritis due to "enteric infection"...
23. what is the most common bacterial cause of bloody diarrhea in the US?
24. what foods is the bacteria from question 23 associated with and how long is the incubation period?
25. what is the clinical picture of enteric infection from the bacteria from question 23?
26. salmonella is associated with which food?
27. shigella is most common in what age group?
28. how long is the incubation period for shigella?
29. why is gastroenteritis due to e.coli difficult to treat?
30. enteropathogenic e.coli invasion is associated with...
31. enterohemorrhagic e.coli invasion is associated with...
32. what are some complications of enterohemorrhagic e.coli and how common are they?
parasitic infections...
33. what are three examples of parasites that might infect the GI tract?
34. how is giardia transmitted?
35. how is giardia related to lactose intolerance?
36. what is the clinical picture of giardia infection of the gut?
37. how is cryptosporidium transmitted?
38. what is the clinical picture of a cryptosporidium infection of the gut?
39. how is entamoeba histolytica transmitted?
40. which patients are at higher risk of infection with entamoeba histolytica?
41. what is the clinical picture of patients infected with entamoeba histolytica?
answers
1. osmotic, secretory, exudative, motility.
2. increased concentration of non absorbable solute in the intestinal lumen (undigested carb's, epsom salts) causes increased osmotic pressure.
3. increased chloride and water secretion, from the inhibition of Na/water absorption, enterotoxins, hormones, laxatives, removed gall bladder.
4. diarrhea with mucous, blood, protein exudate from inflammation or infection.
5. increased or decreased contact between the mucosa and GI contents.
6. dehydration, failure to thrive/malnutrition, abdominal pain, borborygmi, perianal erythema.
7. rotavirus, enteric adenovirus, norwalk virus, calci virus, astrovirus.
8. infectious diarrhea worldwide.
9. winter months.
10. from preformed toxin, toxin formed in vivo, or invasion of mucosa by bacteria.
11. staph aureus, bacillus cereus, cholera, clostridium perfringens and botulinum. [toxigenic staph cereal cool closet] [the staff ate toxic cereal in a cool closet]
12. from food left out for long periods, usually resolves quickly- within hours.
13. chinese food - called "fried rice syndrome".
14. emesis first, then diarrhea. resolves in less than 2 days.
15. 1-3 days after.
16. water, salt, "lite salt", glucose, NaHCO3.
17. beef, beef products, poultry.
18. 12, 3.
19. home-canned foods.
20. freshwater fish.
21. paralysis.
22. 4-8 hours.
23. campylobacter jejuni and fetus.
24. contaminated meat and dairy, 1-7 days.
25. prodrome for 1-2 days with headache and malaise, then severe abdominal pain with fever and watery diarrhea, then bloody diarrhea.
26. unpasteurized raw milk.
27. children 6 months to 5 years.
28. 1-3 days.
29. because treatment antibiotics might simply lyse bacterial cells and release toxic contents, creating greater toxin exposure.
30. nurseries, watery diarrhea.
31. undercooked beef, bloody diarrhea.
32. 5% of cases have hemolytic uremic syndrome or thrombotic thrombocytopenic purpura.
33. giardia lamblia, cryptosporidium, entameoba histolytica.
34. fecal / oral ingesting of cysts, associated with traveling, hypochlorhydria, malnutrition.
35. giardia might produce a celiac like lesion which could interfere with lactose absorption.
36. 1-2 weeks incubation, mild self limiting enteritis with watery diarrhea, bloating, and flatulence.
37. fecal/oral, water, food, pets (cats especially). in most drinking water sources.
38. 5 day incubation, then profuse watery diarrhea and low grade fever.
39. fecal/oral, associated with traveling.
40. institutionalized or immunocompromised.
41. abdominal pain, fever, bloody diarrhea.
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