7. Fecal Analysis Flashcards by Samantha Boyer

normal adult excretes —– g/day of feces

100-200 g

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4 major digestive enzymes from pancrease

trypsin
chymotrypsin
amino peptides/elastase
lipase

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aid in fat digestion

bile salts from liver

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—– mL enters GI tract each day

9000 mL

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fecal electrolyte content is similar to that of…

plasma

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large intestine can absorb around —— mL water

3000 mL

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diarrhea definition (3)

increase in daily stool weight > 200g
liquidity
frequency of > 3x/day

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chronic diarrhea

> 4 weeks

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3 major mechanisms of diarrhea

secretory
osmotic
intestinal hypermotility

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——— = 290 - [2(fecal Na) + (fecal K)]

osmotic gap

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osmotic vs secretory diarrhea

osmo gap

osmotic: ↑ (> 50)
secretory: ↓ (< 50)

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osmotic vs secretory diarrhea

fecal Na

osmotic: ↓ (< 60 mmol/L)

secretory: ↑ (> 90 mmol/L)

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osmotic vs secretory diarrhea

fecal K

osmotic: ↓ K

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osmotic vs secretory diarrhea

osmotic: ↓ (< 5.3)

secretory: ↑ (> 5.6)

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osmotic vs secretory diarrhea

reducing substance

osmotic: +

secretory: =

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osmotic vs secretory diarrhea

stool output

osmotic: ↓ (< 200 g)

secretory: ↑ (> 200 g)

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secretory diarrhea

increased secretion of water
overrides absorptive ability
often infections (enterotoxin-producing—think cholera)

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osmotic diarrhea

poor absorption that exerts osmotic pressure across intestinal mucosa

water and electrolyte retention

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malabsorption and maldigestion contribute to ——– diarrhea

osmotic

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osmotic diarrhea causes

lactose intolerance
laxatives
Mg-containing antacids
amebiasis
antibiotics

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intestinal motility is altered by…

dietary fiber
chemicals
nerves
hormones
emotions

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nerves and muscles of the bowel are extra sensitive

IBS

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causes of hypermotility

enteritis
parasympathetic drugs
complications of malabsorption
secretory & osmotic diarrhea

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causes of constipation

diet
↓ exercise
↓ water, fiber
dairy products
antacids
resisting the urge
stress
long term laxative use
pain medications
IBS
pregnancy
etc

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fecal fat

steatorrhea

absence of bile salts gives > --- g/day of fecal fat

6 g

pale, greasy, bulky, spongy, pasty foul stools

steatorrhea

differentiates malapsorption from pancreatitis as causes of steatorrhea

D-xylose test

low urine D-xylose after ingestion

malabsorption condition

no D-xylose in blood after ingestion (normal)

pancreatitis

3 colorless tetrapyrroles (general name)

urobilinogens conjugated bilirubin --> intestinal bacteria --> urobilinogens

3 urobilinogens

- urobilinogen - stercobilinogen - mesobilinogen

what happens to urobilinogens in the lower GI tract?

spontaneously oxidized to bile pigments ("bilin" form) orange brown color

black stool

upper GI bleed iron therapy charcoal bismuth

red stool

lower GI bleed beets rifampin

pale yellow, white, gray stools

bile duct obstruction barium sulfate

green stools

biliverdin oral antibiotics green veg

claylike white stools

bile duct obstruction pancreatic disorders

ribbonlike stools

intestinal constriction

mucus/bloody mucus in stools

colitis dysentery malignancy constipation

---- WBCs/hpf indicates invasive, inflammatory condition

1-3

-------- bacteria are usually the cause of fecal leukocytes

invasive (not toxin producing, viruses or parasites)

methods for detecting fecal WBCs (3)

wet prep + **methylene blue** (fresh specimen) dried smear + **wright/gram stain** (fresh specimen, permanent slides) **lactoferrin latex agglutination** (refrigerated/frozen specimen)

muscle fiber examination useful in diagnosing... (3)

- pancreating insufficienty (CF) - biliary obstruction - gastrocolic fistulas

-------- slides are used for muscle fiber exam

emulsification

# muscle fiber exam emulsify stool in ---- drops of ---------

2 drops 10% alcoholic eosin

# muscle fiber exam only count...

undigested fibers vertical and horizontal striations > 10 is reported as increased

2 parts of qualitative fecal fat exam why?

- **neutral fat stain**—only neutral fats - **split fat stain**—also stains fatty acid salts (soaps), fatty acids, cholesterol

neutral fat stain

water 95% ethyl alcohol Sudan III

split fat stain

acetic acid Sudan III

how to quantify fats for both types of stain

- neutral: large orange droplets/HPF - split: all orange droplets/HPF

steatorrhea indicated by each stain's droplet count

- neutral: > 60/HPF - split: > 100/HPF

normal neutral stain count elevated split stain count

malabsorption

elevated neutral and split stain count

maldigestion

detects early stages of colorectal cancer

FOBT

amount of occult blood that is clinically significant

2.5 mL/150 g

3 FOBT methods

- Guaiac-based FOBT - Immunochemical FOBT - Porphyrin-based FOBT

point of care FOBT

guaiac

gFOBT relies on the -------- of hemoglobin

pseudoperoxidase

gFOBT false positives

**red meats (myoglobin)** horseradish, melons, broccoli, cauliflower, radishes, turnips aspirin, NSAIDs **rehydration of dried sample prior to developer**

gFOBT false negatives

vitamin C failure to wait for sample to dry

iFOBT relies on the --------- of hemoglobin

globin portion (anti-human Ab)

FOBT with no dietary or medication restrictions

iFOBT

porphyrin FOBT relies on...

conversion of heme to fluorescent porphyrins

FOBT more sensitive to upper GI bleeds

porphyrin

porphyrin FOBT false positives

red meat

confirmatory, quantitative fecal fat test

3-day collection

coefficient of fat retention and reference value

100[(dietary fat - fecal fat)/dietary fat] = coefficient of fat retention should be at least 95%

5 methods of measuring fat in a 3-day collection

**time consuming** - Van de Kamer titration (gold standard) - gravimetric **rapid** - near-infrared reflectance spectroscopy - NMR - acid steatocrit

VDK titration gets ----% of fecal fat

80%

test to find out if blood in neonate stool is from them or from swallowing mom's

APT test (fetal hemoglobin)

positive for fetal hemoglobin

remains pink after alkali treatment (1% NaOH) (mom's Hgb will denature)

3 fecal enzyme tests

- trypsin (not used) - chymotrypsin (not used) - elastase 1

elastase 1 test is an ------- test

ELISA

CHO in stool produces ------ diarhhea

osmotic

2 examples of what can cause CHO in feces

Celiac lactose intolerance

test for CHO in stool

Clinitest screening only; needs to be confirmed with serum test

pH < ----- can correlate with + stool clinitest

5.5

7. Fecal Analysis Flashcards

(78 cards)