Acute Diarrhea/GI infections Flashcards
Where are most nutrients absorbed?
the proximal 100-150 cms
Features of small bowel infection
watery diarrhea, large volume, abd cramping, bloating, gas, wt loss
fever is rare
rare stool WBCs or occult blood
Features of large bowel infection
frequent small regular stools painful BM or tenesmus fever bloody, mucoid stools RBCs and WBC on stool smear
What is the most common etiology of severe community acquired diarrhea?
87% bacterial
Define osmotic diarrhea
neither SI nor LI can maintain an osmotic gradient
electrolyte absorption is not impaired
osmotic gap is present (>100 mosm/kg)
Features of osmotic diarrhea?
can occur due to ingestion of poorly absorbed ions or surgars or sugar alcohols
disappears w/fasting (ie/at night) or cessation of offending substance
monosaccharides but not disaccharides can be absorbed intact across the apical membrane of the intestine
Define secretory diarrhea
small osmotic gap (<50 mosm/kg)
osmolality of colonic fluid contents is in equilibrium with body fluids
Features of secretory diarrhea?
can be causes b either net secretion of anions or inhibition of net sodium absorption, enterotoxins, peptides produced by endocrine tumors
How is the osmotic gap calculated?
2x([Na+]+[K+])
osmotic gap=serum osm - est stool osm
(normal ~290)
What does it mean when the osmotic gap is negative?
poorly absorbed multivalent anion (ie/phosphate or sulfate)
What are signs of surreptitious laxative ingestion?
chemical or chromatographic analysis of stool water
large osmotic gap (suggests magnesium ingestion)
negative osmotic gap
-eating disorders, munchausen, secondary gain (disability)
What are signs that a stool sample may have been tampered with?
if stool osmolarity extremely high-diluted with urine
if stool osmolarity extremely low-diluted with water
What is the number one foodbourne disease in the us? What are features of this pathogen?
salmonella typhi
gram negative encapsulated bacilli
found in poultry, eggs and milk, associated with pet turtles
What type of bacteria is shigella?
gram negative bacilli
unencapsulated, facultative anaerobes
Where is shigella commonly contracted?
daycare and institutional settings or person to person
What is the clinical course of shigella?
check for when trying to dx chrons
self limited
usually affects left colon, maybe ileum too
rarely causes HUS< seizures or reactive arthritis
What are key features of campylobaer jejuni?
leading cause of acute bacterial diarrhea worldwide undercooked poultry, unpasteurized milk, conaminated water incubtion up to 8 days flu like prodrome self limited watery or hemorrhagic diarrhea small and large bowel symptoms reactive arthritis/erythema nodosum guillain barre syndrome pseudoappendicitis
Features of giardia lamblia?
drinking from mountain streams
acute or chronic diarrhea with upper abdominal bloating
small bowel disease
flagellated protzoan
Escherischia coli types?
ETEC (enterotoxigenic e coli)
EIEC (enteroinvasive e coli)
EAEC (Enteroaggregative ecoli)
EHEC (enterohemorrhagic e coli)
What is the principal cause of traveler’s diarrhea?
ETEC
What 2 toxins does ETEC produce?
heat labile & heat stable (LT & ST)
What are key features of EHEC?
aka 0157:H7 undercooked ground beef 39% of cultured pathogens in visibly bloody specimens associated w/HUS potentially worse w/abx
Features of vibrio cholerae?
gram negative contaminated drinking wter seafood assoicated worry about after natural disasters enterotoxin choleratoxin causes disease: opens CFTR leading to more water in the lumen
Describe vibrio cholera infection
usually asymptomatic/mild
severe disease-watery diarrhea and vomiting
incubation 1-5 days
may lose up to 1L/hr
How common is norovirus?
half all gastroenteritis worldwide
from contamination or person to person
schools, cruise ships, etc
What is the leading cause of death worldwide?
rotavirus
-children bwn 6 and 24 mo most vulnerable
vaccines now available
What parasites frequently cause diarrhea?
ascaris lumbricoides
strongyloides
necator americanus and ancylostoma duodenale
What is the leading cause of iron deficiency anemia in the developing world?
necator americanus and ancylostome duodenale
hookworms
What are common causes of diarrhea in immunocomprimised hosts?
parasites-crytp, isospora belli, cyclospora, microsporia
bacteria-salmonella, campylobacer, shigella, mac
viral-cmv, hsv, adenovirus
What is the definition of nosocomial diarrhea?
new diarrhea at least 72 hours after admission
A history of fever directs the DDX to what causes?
invasive bacteria, enteric viruses, cytotoxic organism (C diff, Ent hist), ischemia, IBD
What does diarrhea within 6 hours of eating something indicate?
ingestion of a toxin
ie/staph aureus-potato salad, bacillus cereus-chinese food/rice
What does diarrhea within 8-14 hours of eating something indicate?
clostridium perfringens infection (toxin producing)
Diarrhea that began more than 14 hours after food ingestion indicates what?
viral or bacterial, non specific
When and how to order stool culture for ova and parasites?
when: 3 times, 3 consecutive days (24hrs apart) order w/ persistent diarrhea >14 days travel to mountainous regions exposrue to daycare immune comprimised community waterbourne outbreak
How is infectious diarrhea treated?
oral rehdration (preferred, IV ok) oral rehydration solution-has sal, citrate, bicarb, KCl, glucose & sucrose in water
How to dx EHEC?
need 3 of the following:
- bloody stool
- no reported fever
- WBC >10,000
- abdominal tenderness
What empiric antibiotics are used for travelers diarrhea?
fluoroquinolong or TMP-SMX
What are the indications for empiric antibiotics?
fever, bloody diarrhea, presence of occult blood in stool
When can antimotility agents be used for diarrhea? Which agents do you use?
if fever is absent and stools are not bloody
loperamid or diphenoxylate may be used
What is the risk with giving and antimotility agent?
can facilitate the development of HUS in EHEC
What are some general features of C difficile?
gram positive spore forming anaerobic bacteria
assoc w/use of clinda
cause of anti-biotic associated pseudomembranous colitis
What are risk factors for C diff?
recent abx use age duration of hospital stay chemo IBD AIDS gi surgery or g tube? antacids?
How is Cdiff transmitted?
fecal-oral
What is the time it takes to go from Cdiff exposrue to symptoms?
2-3 days
risk of contraction for weeks after abx though
What toxins does C diff produce?
toxin A-enterotoxin
toxin B-cytotoxin
What is the clinical presentation for C diff?
bloody watery diarrhea fever abd pain leukocytosis pseudomembranous colitis severe-toxic megacolon (stop having diarrhea, ominous sign) sepsis, colonic perforation, death
C diff presention?
wearing gloves
wash hands (not w/hand gel)
isolation gowns
What are the two mainstays of C diff tx?
metronidazole and vancomycin***
What is the rate of C diff recurrence?
10-35%
Options for tx for C diff recurrence?
switch from metronidazole to vancomycin vancomycin taper rifaximin chaser fidaxomicin (lower recurrance, narrower spectrum than vanco) probiotics ?? fecal transplant IVIG (anti IgG anti-toxin A)
What is a common bacterial used as a probiotic for c diff?
sacchromyces boulardii
What is irritiable bowel syndrome?
chronic and relapsing abd pain, bloating, and changes in bowel habits including diarrhea nad constipation
What are lab findings in IBS?
normal cbc, lytes and LFTs
What criteria does a patient’s symptoms have to fit to be IBS?
Rome III Criteria
3days sx/mo in the last 3mo w/2 or more of the follwoing
-improvement w/defecation
-onset associated w/change in freq of stool
-onset associated w/ a change in form (appearance) of stool
What is diverticular disease?
actually pseudodiverticular outpouchings of the colonic mucosa and submucosa
-occurs near where nerves and arterial vasa recta penetrate the inner circular muscle coat to create discontinuities in the muscle wall
Where does diverticular disease usually occur?
sigmoid colon
What occurs when diverticula become inflamed?
diverticulitis
What exacerbates diverticulosis?
diets low in fiber, which reduce stool bulk
What can occur with diverticular perforation?
formation of pericolonic abscesses, development of sinus tracts (fistula), and occasionally peritonitis
What are the symptoms of diverticular disease?
~20% develop symptoms
-intermittent cramping, continuous lower abdominal cramping, continuous lower abdominal discomfort, constipation and diarrhea
Features of acute appendicitis?
males
adolescents/young adults
luminal obstruction/fecalith
ischemic injury and stasis favors bacterial proliferation
Sx of acute appendicitis?
periumbilical pain that moves to RLQ
nausea, vomiting, low grade fever, mildly elevated white count
mcburney’s sign
What causes ischemic colitis?
mucosal infartction -hypotension -arterial spasm transmural infarction -arterial thrombotic/embolitic occlusion
Where does ischemic colitis usually occur?
watershed zones (splenic flexure, sigmoid colon and rectum)
Features of ischemic colitis?
segmental and patchy distribution hemorrhagic and ulcerated mucosa self limited resolves when inciting event resolves older ppl, usually w/coexisting cardiac or vascular disease
What are the symptoms of acute transmural infarction?
sudden severe abd pain and tenderness
sometimes accompanied by nausea, vomiting, bloody diarrhea, or grossly melanotic stool
What cytokines do Th1 cells produce?
IFN-gamma
What cytokines do Th2 cells produce?
IL-4, IL-5, IL-13
What cytokines do Th17 cells produce?
IL-17
