Feces
Feces
It is the waste material passed out from the bowl through
the anus .
Feces is composed of the remaining digested /
undigested food , water ,bacteria and gastrointestinal
tract secretions.
Formation Of Feces;
Chyme passes from the small intestine to the large
intestine , as the chyme moves through the first half of
colon large amounts of water and electrolytes is
absorbed(when 9L of water fluids enter the intestine only
0.1L of water is excreted in feces since most of it is
absorbed in the small intestine and 1/10 is absorbed in
the large intestine .Water absorbtion transforms the
chyme to a mush-like consistancy , then it moves to the
transverse colon and it solidifies further and finally it
passes the descending colon to the anus.

Composition of Feces;
1- Water 75%.
2-Solid 25%.
a)
Solidified components of the digestive juices ,undigested
fibers (e.g celluose) which is insoluble ,acts as bowl
irritant ,draws water out into lumen ,cleans out lower GIT
and is correlated with lower risk of colon cancer.
b) Dead bacteria (20%).
c) Fat (10-20%).
d) Inorganic material (10-20%).
e) Undigested protein(2-3%).

Properties;
Colour; Normal feces has a dark brown colour,
(bilirubin in the presence of bacteria will get
oxidized to urobilin which gives stool its typical
colour)
- Odor; The odor of feces is affected significantly
by the type of food ingested and the bacterial
flora of the individual (of the main order
contributers H2S and mercaptens.
- Consistency; Normal feces is solid to semi-solid
depending on diet.
- 80 - 170 g/day.

Water and electrolytes;
Electrolytes like bicarbonate are secreted by the
wall of the large intestinal lumen, which helps to
neutralize the acidic byproduct of bacterial
metabolism. Na+ and Cl- are absorbed by the
intestinal wall which creats a concentration
gradient that facilitates water absorbtion.
The large intestine only absorbs 8L of water per
day ,the rest will remain in the colon giving feces
a liquid consistency.

Bacteria;
Bacteria in the colon,
- Contributes to the formation and absorption of
vit B12 ,thiamin, riboflavin and vitamin K .
- It digests cellulose producing nutrients that can
be absorbed by the colon.
- It produces gases such as CO2, H2 and methane
which makes flatus (gas) thus contributing to
feces ordor.

Fecal Analysis;
Stool analysis is done to:
 Help identify diseases of the digestive tract, liver , and pancreas. Certain
enzymes (such as trypsin or elastase) may be evaluated in the stool to help
determine how well the pancreas is functioning.

Help find the cause of symptoms affecting the digestive tract, including
prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea,
vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever.

Screen for colon cancer by checking for hidden (occult) blood.

Look for parasites, such as pinworms or Gardia Lamblia.

Look for the cause of an infection, such as bacteria, a fungus, or a virus.

Check for poor absorption of nutrients by the digestive tract (malabsorption
syndrome). For this test, all stool is collected over a 72-hour period and then
checked for the fat and meat fibers. This test is called a 72-hour stool
collection or quantitative fecal fat test.

Fecal Specimen collection;
The patient is given a proper sample collection
container ,which is clean, dry, sealable and leak
proof . The stool sample should not be
contaminated with urine or water (urine can
destroy protazoa).
Fecal Analysis Methods;

1- Gross Examination ; The gross examination provides clues
to possible GI disorders .
a)Colour; Black colour may indicate old blood from the upper
GIT , whereas bright red blood in feces indicates blood
from the lower GIT.
A very pale stool indicates biliary obstruction , or a barium
sulfate enema.
The presence of blood streaked mucus or pus
often accompanies bacterial or amebic dysentery.
 b)Consistancy ; A ribbon like fecal specimen
could indicate irritable bowl syndrome or GIT
obsruction.
2-Microscopic examination;
a)Fecal leukocytes, especially neutrophils are
associated with dysenttery. They can be detected
by dried smears of the stool stained with gram
stain.
Fecal
leukocytes
White blood cells in a stool sample
stained with Methylene Blue
2-Microscopic examination;
Meat fibers ; Increased undigested food such as meat
fibers and vegetables correlate with mal digestion , and
patients with hypermotility , pancretitis…..
Increased meat fibers can be recognized microscopically
as they are rectangular with the cross striations typical of
muscle fibers.
3- Chemical analysis;
a)Occulent blood, fecal blood is found in
infection,trauma, colorectal cancer, ulcers
hemorrhoids. Blood can be detected by many
tests the best test is the guaiac impregnated
paper in a card board holder .Patients should be
instructed to avoid red meat, turnips, horse
raddish, asprin, vitC as they interfere with the
test .
 guaiac test; A thin layer of feces is applied to a thick
piece of paper attached to a thin film coated with guaiac.
Both sides of the test card are peeled open, to access the
inner guaiac paper. One side of the card is marked for
application of the stool and the other is for the developer
fluid .After applying the feces, one or two drops of
hydrogen peroxide are then dripped on to the other side of
the film, and it is observed for a rapid blue color change.
When the hydrogen peroxide is dripped on to the guaiac
paper, it oxidizes the alpha-guaiaconic acid to a blue
colored quinone. When no blood or peroxidases ,or
catalases from vegetables are present this oxidation occurs
very slowly .Heme found in blood catalyzes this reaction
giving a positive result in two seconds . Therefore a
positive result is one where there is a quick and intense
blue color change of the film.


The guaiac test can often be false positive which is a
positive test result when there is in fact no source of
bleeding. This is particularly common if the recommended
dietary preparation is not followed, as the heme in red
meat or the peroxidase or catalase activity in vegetables,
especially if uncooked, can cause analytical false positives.
Vitamin C can cause analytical false negatives due to its
anti-oxidant properties inhibiting the color reaction.
Other tests for fecal blood include ; benzidine , orthotoluidine
……., but they are very sensitive thus they lead to many
false positive results.
guaiac test;
Both square test areas in
the upper area of the card
show the intense blue
color of a positive result.
The lower two smaller
circular areas on the
orange stripe are
analytical control
reactions, positive on the
left and negative on the
right, that help assure
that the card and
developer bottle have
been maintained in proper
conditions and have not
been damaged before the
test is performed
Fecal Analysis Methods;
b) Fetal Hemaglobin ; Newborns may excrete stool
containing blood . This could originate from the maternal
blood ingested at delivery or from the newborns own GIT.
Differentiating between these two sources of blood is
important for the newborns survival.
To determine whether it is fetal Hemoglobin (Hb F) or
maternal Hemoglobin (Hb A) . The stool is mixed with
waterto yeild a pink supernatant . The supernatant is
removed and then alkalinized with dilute NaOH , if the
pink color remains , the blood contains fetal Hemoglobin
(Hb F) , if the pink color changes to yellow or brown
within two minutes the Hb is maternal Hemoglobin (Hb
A) .
Fecal Analysis Methods;
c)Fecal CHO ; Disaccharides are osmotically active and
trigger movement of alarge amount of water to the
intestines , when present in the colon .Fecal CHO are
present in Celiac disease , and lactose intolerance.
The CHO test is most useful in infants to diagnose chronic
diarrhea cases which could be caused by e.g Celiac
disease , and lactose intolerance .
CHO in feces is detected by the Copper reduction test , to
detect reducing sugars , if positive infant is tested by
more specific serum tests.
If CHO is present the pH of feces drops from pH 7 or 8 to
a pH below 5.5.
Stool analysis
Stool analysis
Normal:
The stool appears brown,
soft, and well-formed in
consistency.
The stool does not
contain blood, mucus,
pus, harmful bacteria,
viruses, fungi, or
parasites.
The stool is shaped like a
tube.
The pH of the stool is
about 6.
The stool contains less
than 2 milligrams per
gram (mg/g) of sugars
called reducing factors.
Abnormal:
The stool is black, red, white,
yellow, or green.
The stool is liquid or very hard.
There is too much stool.
The stool contains blood,
mucus, pus, harmful bacteria,
viruses, fungi, or parasites.
The stool contains low levels of
enzymes, such as trypsin or
elastase.
The pH of the stool is less than
5.3 or greater than 6.8.
The stool contains more than 5
mg/g of sugars called reducing
factors; between 2 and 5 mg/g
is considered borderline.
The stool contains more than 7
g of fat (if your fat intake is
about 100 g a day).