Fecal Analysis and Diarrhea Evaluation

How many fluids/day pass through the GI tract

10L

What does diarrhea occur 2° to?

interruption of absorption-secretion cycle

Why does infectious diarrhea occur?

When one of the 4 mechanisms fails:

1. increased acidity of the stomach

2. rapid transit time of the small bowel

3. illeocecal valve inhibits bacteria from the large intestine from going backward

4. normal flora compete with and inhibit growth of new bacteria

What are the normal enteric flora?

- Enterococcus

- E. coli

- proteus

- pseudomonas

- S. aureus

- candida albicans

- bacteroides

- clostridium

How do we get sick from GI pathogens?

microorganisms are ingested and infect

How does Shigella infect?

through acid resistance

How does chlorea and e. coli infect?

ingestion in large numbers

What's a general way microorganisms can infect?

ingestion with food and partially protected from stomach acid

True or False: direct invasion is the only way to infect

false; some invade the gut mucosa, which would be direct, while others produce toxins (toxigenic) that cause symptoms

What are the types of diarrhea?

1. osmotic

2. secretory

3. motility disorder

What is osmotic diarrhea?

presence of nonabsobabel intraluminal molecules decreasing water absorption from the lumen; volume decreases with fasting

What are examples of osmotic diarrhea?

lactose intolerance, increased sorbitol use

What is secretory diarrhea?

Impaired absorption or excessive secretion of electrolytes, often leads to massive loss of sodium and potassium, copious watery diarrhea without pus or blood; volume does not decrease with fasting

What are examples of secretory diarrhea?

endocrine disorders, zollinger-ellison syndrome, laxatives, bile salt malabsorption

What is motility disorder diarrhea?

fast transit, slow transit

What is fast transit in a motility disorder, and some examples?

reduced contact; hyperthyroid, s/p gastrectomy, IBS

What is slow transit motility disorder, and some examples?

bacterial overgrowth; DM especially, hypothyroid, scleroderma

How to collect a stool sample?

- collect in a bedpan, if bed-bound

- transfer sterile containers

- no urine or toliet tissue or toliet water

What is inflammatory diarrhea?

inflammation of the bowel results in outpouring of necrotic mucosa, colloid fluid and electrolytes, "dysentery"

What are infectious (bacterial) diarrhea etiologies?

- salmonella

- shigella

- campylobacter

- yersinia

- E. coli

- clostridium

- staphylococcus

What are the infectious (parasites and viruses) diarrhea etiologies?

- hookworm: parasite

- tapeworm: parasite

- giardia: protazoa

- cryptosporidium: protazoa

- rotavirus: viral

- norovirus: viral

Why may fecal fat be low?

Recent barium administration for imaging (will cause a temporary decrease), also fiber laxatives/supplementation

What can D-xylose absorption differentiate between?

malabsorption vs. maldigestion

What does D-xylose absorption evaluate?

absorptive capability of intestines

When is D-xylose decreased?

malabsorptive disease, short bowel syndrome

What are the different ways to seperate evaluation of stool for infectious organisms?

- ova and parasite

- culture

- specific etiology testing that requires special medium

How is the ova and parasite evaluated?

microscopic evaluation with wet mount +/- stain

True or False: a regular stool culture requires 3 evaluations and a ova and parasite requires 1?

false; regular = 1; ova and parasite = 3

What are stool cultures useful for?

bacterial etiologies

What do stool cultures do?

isolation of organisms for identification and antibiotic sensitivities

How are ways C. diff can be diagnosed?

- toxigenic culture (stool)

- stool EIA for toxin A and B

- cytotoxicity assay (toxin B)

- PCR assay

What is the gold standard C. diff diagnostic?

toxigenic culture

What do toxigenic culture do?

isolate toxin-secreting isolates of C. diff, but takes a while so it's done among others

What is the C. diff diagnostic stool EIA for toxin A and B?

rapid test, but less senstiive

What is the cytotoxicity assay (toxin B) for C. diff diagnositcs?

a tissue culture

What is the PCR assay for C. diff diagnostics?

detects C. diff toxin B gene; rapid, expensive, possible false negatives

What is norovirus?

RNA virus that causes acute-often severe projectile gastroenteritis

What is norovirus common in?

travel/cruises

What are the symptoms of norovirus?

profuse vomiting + water diarrhea + nausesa

What are the testing options for noroviruses?

- immunoassay evaluation

- PCR assay

- visualization by electron microscopy

Why is norovirus not really diagnosed much?

it's more clinical, because it's done in like a day, so by the time we're testing, the symptoms have resolved anyway

How is the immunoassay evaluation in norovirus?

not sensitive

How does the PCR assay work in norovirus?

detects RNA in vomit or stool; most widely used

What is Enterobius known as?

pinworms

What are enterobius (pinworms)?

parasitic infection, common in children and instituionalized populations

What does enterobius (pinworms) cause?

intesnse night-time anal itching

Why does enterobius (pinworms) affect kids at night?

because they're nocturnal, so they're moving at night

What is done for enterobius (pinworms)?

Tape test: apply scotch tape to perianal area first thin in morning, eggs should be visible on the tape

How is Enterobius (pinworms) evaluated?

ova and parasite evaluation

What way is Cryptosporidium usually found?

typically water-borne

What is Cryptosporidium resistant to, and who does it mostly affect?

resistant to chlorination; affects mostly immunocompromised

How does inflammatory diarrhea occur?

inflammation of the bowel results in outpouring of necrotic mucosa, colloid fluid and electrolytes, "dysentery"

What types of inflammatory diarrhea can be represented by frequent bloody stools + systemic symptoms?

shigella, salmonella, campylobacter, E. coli, C. diff, IBD

What types of noninflammatory diarrhea can be represented by copious watery diarrhea without pus or blood + systemic symptoms?

enterotoxins, laxatives, fatty acid metabolites

How does noninflammatory diarrhea occur?

impaired absorption or excessive secretion of electrolyte, often leads ot massive loss of sodium and potassium

What is malabsorption?

markedly reduced absorptive capability; fast trasnit time; fats are not well-absorbed

What can cause malabsorption?

chron's disease, short gut

What is maldigestion?

generally secondary to obstruction in pancreatobiliary tree or short gut

What causes maldigestion?

tumor, gallstones

What is fecal fat testing used for?

to evaluate patients with steatorrhea; measures fat content in stool

What is the normal amount of fat in the feces?

2-7 g/24 hours

What is needed in fecal fat testing?

3-day stool collection

What causes increased fecal fat interpretation?

- cystic fibrosis

- malabsorption

- maldigestion

- short gut syndrome

- enema and laxative (mineral oil) use

What are the malabsorption issues that cause increased fecal fat interpretation?

celiac disease, Crohn's disease, whipple disease (tropheryma whipplei, rare bacterial infection)

What are the maldigestion issues that cause increased fecal fat interpretation?

bile duct obstruction or pancreatic duct obstruction

What is d-xylose?

a monosaccharide that is easily absorbed in normal intestines

What happens to d-xylose in malabsorption?

D-xylose absorption is diminished

What do you measure d-xylose absorption with?

serum and urine levels

What is d-xylose used for?

to differentiate between maldigestion and malabsorption

How does D-xylose absorption work?

- baseline serum and urine collection

- patient drinks water with set amount of D-xylose

- collect serum specimen (1hr in peds, 2hrs in adults)

- collect urine specimen (5hrs)

What is the required collection for ova and parasites?

collection of minimum of 3 specimens over 10 days (every other day)

What are some IDs that could be made from the ova and parasite?

- cryptosporidium

- cyclospora

- giardia

- helminths (parasitic worms)

What bacterial etiologies require a special media/culture technique in stool cultures?

- yersinia

- E. coli 0157:H7

- vibrio

Why does C. diff occur?

bacterial overgrowth associated with antibiotic use/extended antibiotic use

How does C. diff occur?

toxins released causes necrosis of colonic epithelium, this leads to pseudomembranous colitis

What are the two types of C. diff, and what causes each?

toxin A: enterotoxin

toxin B: cytotoxin

What are the s/sxs of C. diff?

high volume, watery diarrhea

How is C. diff diagnosed?

flexible sigmoidoscopy/colonoscopy

What is visualized when a patient has C. diff?

typical pattern is numerous raise, yellow plaques; "pseudomembranous colitis"

What is Salmonella?

foodborne enteropathogen

How is Salmonella diagnosed?

- stool culture

- total antibody EIA

What does the stool culture for Salmonella tell us?

the actual subtype of salmonella

What does the total antibody EIA (serum) do for salmonella?

detects anitbodies to salmonella

What do the agglutinin titers have to be in Salmonella to be positive?

>1:160 positive

What is Shigella?

foodborne enteropathogen

How is Shigella diagnosed?

stool culture

What is the most common cause of enteritis?

E. coli

Where can E. coli be found?

environment, foodborne, and GI tracts of animals and humans

What are the 3 different E. coli infection categories?

1. enterohemorrhagic (EHEC)

2. enteropathogenic (EPEC)

3. enterotoxigenic (ETEC)

What is enterohemorrhagic (EHEC) E. coli?

subtype of e. coli that produces a toxin called shiga toxin

What does Shiga toxin often produce?

severe disease with bloody diarrhea, hemolytic/uremic syndrome

Who is most affected by EHEC?

children and elderly

What is EHEC often associated with?

pockets of larger outbreaks

How is EHEC diagnosed?

stool culture + stool for identification of shiga toxin

What is EPEC desecribed as?

watery or bloody diarrhea?

Who is EPEC common in?

international travel and children

How is EPEC diagnosed?

stool culture

What ETEC the leading cause of?

traveler's diarrhea

How is ETEC transmitted?

via contaminated food or water supplies

How is ETEC described?

water diarrhea?