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23. Acute Diarrhea Flashcards

1
Q

Infectious diarrheal disease is the ___ leading cause of death worldwise
____ leading cause of childhood death

A

Second

First

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2
Q

What is the time frame for acute diarrhea/

A

<14 days

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3
Q

What is the definition for diarrhea?

A

> 200 grams per 24 hour period

3 or more loose/watery stools per day or clear increase in frequency over baseline

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4
Q

When does most diarrhea occur?

A

Winter months (viral)

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5
Q

WHat is the length of the SI? What is mostly absorbed there?

A

3-8 meters

Macronutrients: carbs, fat, nitrogen **absorbed in the proximal 100 to 150 cm

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6
Q

How much of the 10 L of chyme that under the duodenum exits the SI?
Consequence on pathology in this area?

A

1.5 L

SI does the bulk of the absorption, therefor pathology is very dramatic there

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7
Q

S/s of infections in the small bowel?

A

Large volume of watery diarrhea
Abdom cramping, bloating, gas, and weight loss
**fever is rare
**rare stool WBCs/occult blood

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8
Q

S/s of infections in the large bowel?

A 
Frequent, small, regular stools
Painful BM of tenesmus (painful urge to have a BM)
Fever
Bloody and mucoid stools
RBCs and WBCs on stool smear
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9
Q

What is the infectious cause of most gastroenteritis?

A

Viral (cultures only positive in 1.5-5.6 cases

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10
Q

What is the definition of severe, community acquired diarrhea?

A

> 4 fluid stools per day
3 days
87% bacterial

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11
Q

What are the bacterial agents that commonly cause acute GI illness?

A 
Salmonella
Shigella
Campylobacter
C. difficile
E. coli 0157:H7
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12
Q

What are the viruses that commonly cause acute GI illness?

A

Adenovirus (40 and 41)
Rotavirus
Calcivirus
Astrovirus

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13
Q

What are the protazoa that commonly cause GI illness?

A

Giardia
Cryptospoidium
Entomoeba histolytica

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14
Q

What are the two viruses that cause colon infection in immunocompromised people?

A

CMV

HSV

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15
Q

What are non-infectious causes of diarrhea?

A 
Drugs-antibiotics, laxitives 
Food allergies 
IBD/IBS
Thyoid disease
Carcinoid/Neuroendocrine tumors
Ischemic colitis 
Stool impaction-overflow diarrhea
Stress
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16
Q

What happens with osmotic diarrhea?

A

Neither SI nor colon can maintain an osmotic gradient

Unabsorbed ions in the lumen cause water retention

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17
Q

What SHOULD the intraluminal osmolality be?

A

290 mOsm/kg

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18
Q

What are some things that can cause osmotic diarrhea?

A
  • Ingestion of poorly absorbed ions or sugar alcohols (mannitol, sorbitol, Mg, sulfate, phosphate)
  • Disaccharidase deficiency (lactase deficiency)
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19
Q

What causes cessation of osmotic diarrhea?

A

Fasting

Cessation of the offending substance

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20
Q

Electrolyte concentrations in stool water with osmotic diarrhea

A

Low concentrations, because electrolyte absorption is not impaired

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21
Q

What is the problem underlying secretory diarrhea?

A
  • Net secretion of anions (Cl- or bicarbonate)

- Inhibition of net sodium absorbtion

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22
Q

What is the most common cause of secretory diarrhea?

A

Infection

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23
Q

What are three actions of enterotoxins that cause secretory diarrhea?

A
  1. Interact with receptors and modulate intestinal transport
  2. Block specific absorbative pathways in addition to stimulating secretion
  3. Inhibit Na+/H+ exchange in the SI and colon
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24
Q

How is the osmotic gap calculated?

A

Gap=Serum Osm - estimated stool Osm (2 x ([Na]+[K]))

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25
Q

What is a normal sized osmotic gap that can result from not being able to count all of the cations?

A

Under 50 mOsm/kg

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26
Q

What kind of osmotic gap will be present in osmotic diarrhea?

A

Over 100 mOsm/kg

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27
Q

What causes a negative osmotic gap?

A

Poorly absorbed multivalent anion like phosphate or sulfate

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28
Q

Why is measured stool osmolality of little value?

A

Tends to rise once the stool has been collected due to continuing bacterial fermentation in vivo

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29
Q

What kind of laxitive can cause a large osmotic gaP?

A

Magnesium

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30
Q

What is useful to look at to see if stool samples have been diluted with urine in the case of laxitive injestion?

A

Stool osmolarity (very high if stool is diluted with urine)

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31
Q

What is the #1 foodbourne illness in the US?

A

Salmonella typhi

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32
Q

What is salmonella typhi infection assoc with?

A

Poultry, milk, eggs

Pet turtles

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33
Q

People with salmonella typhi infection have increased risk for:

A

Gallbladder colonization and gallstones

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34
Q

Patients with sickle cell disease have an increased risk for:

A

Salmonella osteomylitis

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35
Q

Sx of acute salmonella typhi GI infection:

A

Anorexia, ab pain, bloating, N/V, bloody diarrhea

**Colonic/dysenteric like illness despite small bowel disease

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36
Q

What area of the GI does shigella most commonly infect/

A

Left colon, ileum might also be involved

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37
Q

What is shigella rarely assoicated with? (3)

A

HUS
Seizures
Reactive arthritis

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38
Q

What is the leading cause of acute bacterial diarrhea worldwide?

A

Campylobacter jejuni

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39
Q

What are three things that can result from Campylobacter jejuni infection?

A

Reactive arthritis or erythema nodosum
Guillian Barre syndrome
Pseduoappendicitis (bad abdominal pain)

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40
Q

What is the most common pathogenic parasitic infection in humans?

A

Giardia lamblia

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41
Q

How is giardia lamblia acquired? Presentation?

A

Drinking unfiltered/rural water

Acute/chronic diarrhea with upper abdominal pain

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42
Q

What are the 4 kinds of E. coli infections?

A

Enterotoxigenic (ETEC)
Enteroinvasive (EIEC)
Enteroaggregative (EAEC)
Enterohemorrhagic (EHEC) 0157:H7

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43
Q

What type of E. coli resembles shigella and produces blood diarrhea?

A

Enteroinvasive (EIEC)

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44
Q

What type of E. coli attaches to enterocytes via adherence fimbriae

A

Enteroaggregative (EAEC)

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45
Q

What type of E coli is associated with HUS?

A

Enterohemorrhagic (EHEC)

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46
Q

What are the two toxins that Enterotoxigenic E coli has?

A

Heat-labile: like cholera toxin

Heat-stabile: increased IC cGMP with effects similar to cAMP electations by LT

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47
Q

How does the cholera enterotoxin cause disease?

A
  • Increase in IC cAMP
  • Opens CFTR
  • Releases Cl- into lumen and water follows
48
Q

What causes about half of all gastroenteritis outbreaks worldwide

A

Norovirus

49
Q

What is the principal cause of traveller’s diarrhea?

A

Enterotoxigenic E coli

50
Q

Who is most susceptible to rotavirus infection?

A

Children between 6 and 24 months

51
Q

What is an extra-GI sx that ascaris (nematode) can cause?

A

Ascaris pneumonitis (cough)

52
Q

What causes stronyloides infections to persist?

A

Autoinfection: Adult worms in the intestines lay eggs that hatch and release larvae that penetrate the mucosa

53
Q

What is the leading cause of IDA in the developing world?

A

Hookworms like Necator americanus and Ancylostoma duodenale

54
Q

What are some parasites that are more likely to infect patients with lymphoma, BMT, HIV?

A

Cryptosporidium parvum
Isospora belli
Cyclospora
Microsporia

55
Q

What are some bacteria that are more likely to infect patients with lymphoma, BMT, HIV?

A

Salmonella
Campylobacter
Shigella
MAC (myobacterium avium complex)

56
Q

What are some viruses that are more likely to infect patients with lymphoma, BMT, HIV?

A

CMV
HSV
Adenovirus

57
Q

What defines nosocomial diarrhea?

A

New diarrhea at least 72 hours after admission

**increases the length of stay, severity depends on age

58
Q

What is the most common cause of nosicomial diarrhea?

A

Clostridium difficile

**also tube feeds, meds, fecal impaction, ischemic colitis, and CMV/HSV/GVHD in BMT transplants

59
Q

What does diarrhea within 6 hours of eating suggest?

A

Ingestion of a toxin–S.aureus in potato salad or Bacillus cereus in Chinese food/rice

60
Q

What does diarrhea at 8-14 hr after eating suggest?

A

Clostridium perfringens

61
Q

What is needed for diagnosis of the etiology of infectious colitis?

A

CULTURE

**endoscopy not indicated

62
Q

What is a stool culture indicated?

A
  • Severely ill
  • Outbreaks
  • Hospitalization requirement
  • IC patients
  • Comorbidities
  • IBD
  • some employees
63
Q

Why are there many false negatives for ova and parasites? What must be done because of this?

A 
Ova shed intermittantly
Repeated 3x (3 consecutive days, 24 hr apart)
64
Q

When should stool for O and P be ordered?

A 
Persistent diarrhea >14 days
Travel to mountainous regions
Exposure to infants in daycare
Immune-compromised 
Community waterborne outbreak
65
Q

What are ELISAs or DFA good at identifying in the school?

A

Giardiasis

Cryptosporidium

66
Q

What is the key aspect of treatment for diarrhea?

A

HYDRATION

67
Q

What are the important factors for oral rehydration in diarrhea tx?

A

Intestinal glucose absorption via sodium-glucose cotransport remains intact
Intestine able to absorb water if glucose and salt are present

68
Q

What is the Na/glucose cotransporter on the apical surface?

A

SGLT-1

69
Q

How does EHEC presentation differ from the other E coli infections?

A

Bloody stool
NO fever
WBC >10,000
Abdominal tenderness

70
Q

Why is it important to distinguish between EHEC and the other E. colis?

A

Don’t want to give EHEC antibiotics–precipitates HUS

71
Q

Presentation and Tx for traveller’s diarrhea (enterotoxic E.coli)

A

> 4 stools daily with fever, blood/pus/mucus in stool

Prompt tx with fluoroquinolone or TMP-SMX (reduces duration from 3-5 to 1-2 days)

72
Q

What are the indications for empiric antibiotics for diarrhea? What antibiotic?

A

Fever, bloody diarrhea, and the presence of occult blood or fecal leukocytes in the stool
**except for C. diff and EHEC
Fluoroquinolone for 3-5 days (azithromycin and erythromycin if there is resistance)

73
Q

What are two antimotility agents?

A

Loperamide

Diphenoxylate

74
Q

When is the only time that antimotility agents should be used?

A

If fever is absent and stools are NOT bloody

75
Q

What happens if you use antimotility agents for EHEC?

A

Facilitates the development of HUS

76
Q

Classification of C. diff

A

Gram + spore forming anaerobic bacteria

77
Q

Transmission of C. diff?

A

Fecal oral

78
Q

What % of inpatients have asymptomatic colonization with C diff? Outpatients?

A

7-26%

2%

79
Q

Why do newborns have a high carrier rate but don’t get infected?

A

Don’t have the receptors that the toxins bind to, don’t get sick

80
Q

How many days from exposure to sx with c diff?

A

2-3 days

81
Q

Of the C. diff spores and vegetative cells ingested, which one makes it to the small bowel?

A

Spores can survive the stomach acidity and germinate in the small bowel upon exposure to bile acids

82
Q

Where does C. diff colonize?

A

Colonic mucosa

83
Q

What happens after antibiotics destroy normal bacterial flora?

A

C. difficile grows and secretes toxins
Toxins inflame and ulcerate the mucosa
Damaged mucosa secretes fluid that causes the diarrhea

84
Q

What are the toxins produced by C. difficile?

A

Toxin A: potent enterotoxin
Toxin B: cytotoxin in vitro
Binary

85
Q

What C diff toxin is typically tested for?

A

Toxin B

86
Q

What are characteristics of the hypervirulent C. diff strain

A

BI/NAP1/027 strains have 16x more toxin A and 23x more toxin B
tcdC gene mutation may have increased toxin levels
Increased fluoroquinolone resistance

87
Q

What are the typical clinical feautures of C. diff colitis?

A 
Bloody, watery diarrhea
Fever
Ab pain
Leukocytosis (VERY HIGH)
Pseudomembrinous colitis
88
Q

What are the features of severe forms of C. diff infections ?

A

Toxic megacolon
Sepsis
Colonic perforation
Death

89
Q

Important modes of prevention of C. diff?

A

Gloves
HAND WASHING (alcohol based gels don’t work)
Minimize antibiotic exposure (esp quinolones)

90
Q

What are the mainstay therapies for primary C. diff?

A

Vancomycin
Metronidazole
**similar efficacy, but vanco is slightly more effective for severe cases

91
Q

Severe C diff disease is defined as any one of the following:

A
  1. Age over 65
  2. Creatinine over 1.5 times baseline
  3. WBC > 15K
92
Q

What percent of patients with C. diff will have recurrence of sx after intial infection?

A

10-35%

93
Q

What are risk factors for recurrence of C diff infection?

A 
COntinued antibiotics (prevent reest of normal flora)
Age and comorbidities 
Antacid medication
Immunosuppression
Immunodeficiency
94
Q

What are the options for tx of recurrence of C diff

A

Repeat initial therapy
Switch to vanco
Vanco taper (allow good bacteria to return)
Rifaximin chaser (follows vanco)

95
Q

What is an alternative to vanco for C diff that inhibits RNA pol, but lacks activity vs gram negative bacteria, preserving some natural flora?

A

Fidaxomicin (low serum conc, high fecal concentration)

  • *has better protection against recurrence than vanco
  • *too expensive
96
Q

What are the risks of using probiotics for protecting against C diff recurrence?

A

Fungemia from sacchromyces
Endocartitis from lactobaccilus and bifidobacteria
**in IC and critically ill patients

97
Q

What is the probiotic that is MC used following C diff tx?

A

Sacchromyces boulardii

98
Q

What antibodies increase following C diff infection?

A

Anti-toxin A and B antibody levels

**High IgA anti-toxin A is 48x more protective than low levels

99
Q

What is the MOA of IVIG for C diff?

A

Neutralization of toxin A thorugh IgG anti-toxin A antibodies
**good choice for patients that are immunosuppressed

100
Q

What is IBS?

A

Recurrent and relapsing abdominal pain, bloating, and change in bowel habits including diarrhea and constipation

101
Q

Causes of IBS

A

Psychologic stressors
Diet
Abnormal GI motility
Visceral hypersentitivity

102
Q

When does IBS manifest? Labs?

A

20-40 yo in females

Labs all normal, normal endoscopy

103
Q

What is the Rome III criteria for IBS?

A

Recurrent abdominal pain or discomfort 3 days/month in the last 3 months along with 2 or more of the following:

  1. Improvement with defecation
  2. Onset assoc with change in BM frequency
  3. Onset assoc with change in appearance of stool
104
Q

What happens in diverticular disease?

A

Pseudodiverticular outpouching of the colonic mucosa and submucosa
Nerves and arterial vasa recta penetrate the inner circular muscle coat to create discontinuities in the muscle wall

105
Q

Who gets diverticular disease? Under what conditions? Exacerbated by:

A 
Older people (505 in Western adult populations over 60)
Conditions of elevated intraluminal pressure in the sigmoid colon, exacerbated by diets low in fiber which reduces stool bulk
106
Q

What region of the colon is MC affected by diverticular disease?
Obstruction of diverticula leads to:

A

Sigmoid colon

Diverticulitis

107
Q

What can happen with perforation in diverticulitis?

A

Pericolonic abscesses
Sinus tracts
Peritonitis

108
Q

Sx of diverticular disease?

A

Usually asymptomatic

20%: cramping, lower abdominal discomfort, constipation, diarrhea

109
Q

What might prevent development of diverticulitis from diverticular disease? Tx if diverticulitis develops?

A

High fiber diet

Resolves spontaneously or after antibiotic tx

110
Q

What causes appendicitis in 50-80% of cases?

A

Overt lumenal obstruction like a stonelike mass of stool (fecolith)

111
Q

What is the name for the point where abdominal pain focuses in appendicitis?

A

McBurney’s point: right lower quadrant

112
Q

What is McBurney’s sign?

A

Deep tenderness noted at 2/3 the distance from the umbilicus to the right anterior iliac spine

113
Q

What causes mucosal infartion ischemic colitis? Transmural infarction?

A

Hypoperfusion: hypotension or arterial spasm

Arterial occlusion: thrombosis or embolis

114
Q

What are the two watershed regions that are particularly susceptible to ischemic colitis?

A
  1. Splenic flexure (SMA to IMA)

2. Sigmoid colon and rectum (IMA to pudendal)

115
Q

What will be seen on endoscopy with ischemic colitis?

A

Segmental and patchy hemorrhage/ulceration of the mucosa

Linear ulcerations

116
Q

Who gets ischemic colitis?

A

Older people with coexisting cardiac or vascular disease

117
Q

How does acute transmural infarction causing ischemic colitis manifest?

A

Sudden, severe abdominal pain and tenderness

Sometimes accompanied by nausea, vomiting, bloody diarrhea, or grossly melanotic stool

GI (28 decks)

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