Fecal analysis

What does examination of feces examine? Like what organ are we examining?

Gastrointestinal tract (GIT)

How many grams of feces we pass daily and what is feces consist of?

• 200-300 grams

• Consists of: undigested food, intestinal bacteria, GI secretions, and bile pigments + H20

What are the major players of the gastrointestinal tract and what are their functions?

• small intestine functions in digestion and absorption of food

• large intestine functions in absorption of water, sodium, and chloride

Since not all liquid that passes through the GIT is absorbed by the large intestine, what would happen if excess liquid passes through the large intestine?

the excess liquid causes watery stool —> diarrhea

Decreased intestinal mobility permits water reabsorption which result in ______, with this, fecal specimen are small, hard, and often spherical (______).

constipation, scybala

What are the three classes of diarrhea?

• secretory: increased intestinal secretion of a solute

• osmotic: ingestion of an osmotically active solute (sodium/salt)

• intestinal hypermotility

What is the equation for osmotic gap?

osmotic gap= measured osmolality — [2 x (Na + K)]

lets say that the calculated osmotic gap ended up calculating to 16. What type of diarrhea would this be?

this would be secretory diarrhea because the difference between measured and calculated fecal osmolality is between 10-20 mOsm/kg

The osmotic gap ended up being 22 mOsm/kg. What type of diarrhea is this?

This is osmotic diarrhea because the difference between measured and calculated fecal molality exceeds 20 mOsm/Kg

What can cause secretory diarrhea?

• enterotoxin-producing organisms

• intestinal mucosal damage (drug induced or disease related)

• neoplasms (abnormal growth of a tissue)

• drugs or hormones (caffeine)

what are some causes of osmotic diarrhea and what are the types there is?

• Maldigestion: inability to convert food into absorbable substances. It can be caused by pancreatic or hepatic diseases where fat emulsification and lipase activation are deficient or lacking (enzymes).

• Malabsorption: inadequate intestinal absorption of already processed foods. Can be caused by parasitic infection (i.e. Giardia lamblia) or mucosal diseases such as (celiac sprue, ulcerative colitis, crohn’s disease)

what is intestinal hypermotility and what causes it?

• it when transit time is too short to allow normal reabsorption

• It can be caused by: secretory or osmotic diarrhea, laxatives, parasympathetic nerve, stress, increased dietery fiber, and cardiovascular drugs.

what is steatorrhea?

It is feces that is characteristically pale, greasy, bulky, spongy, or pasty and foul smelling. Fecal fat comes from diet, gastrointestinal secretions, bacterial by-products, and sloughed intestinal epithelium.

So if stool is watery and loose it is _________. If stool is greasy, bulky, and has foul odor it is _______.

diarrhea, steatorrhea

so what if fecal WBCs are present/not present in diarrhea?

present WBCs indicate we need a stool culture. absent WBCs indicate parasites or viruses

so what if the three day collection of feces for a test for steatorrhea is normal or abnormal?

normal leads to diarrhea. abnormal means we need more testing to rule out hepatobiliary disease further leads to xylose absorption test. normal means maldigestion and abnormal means malabsorption.

what are the abnormal colors of feces and what do they mean?

• white/clay: problem with liver or bile ducts

• yellow: post hepatic obstruction or barium presence

• green: a lot of green veggies are eaten or antibiotic therapy

• red: blood, beets, food dyes, or certain drugs

• black: blood, iron therapy, pepto-bismol

What are the ways to record feces?

“soft”, “loose”, or “watery”

What causes for feces to have mucus?

constipation or gastrointestinal diseases (colitis, intestinal TB, bacillary dysentery, neoplasms)

What are some causes of odor in feces?

• normal flora is disrupted

• steatorrhea has foul smelling odor due to undigested lipids

what are the types of exams done on feces, stains, and what are they for?

• fecal leukocytes (wright’s or methylene blue stains): presence of neutrophil indicate inflammation

• fecal fat (sudan III/IV, oil red O stains): screen for fat in feces

• fecal blood (Guaiac test): can help detect occult/hidden blood

• fetal fecal hemoglobin (APT test): based on fetal hemoglobin resistance to alkali denaturation which helps differ from maternal source of blood

• fecal carbohydrates (clinitest): testing for reducing carbohydrates to see if patient has deficient or defective enzyme carbohydrates that are excreted in feces