Stool Examination:- Part 2 – Normal Stool Findings

Sample 

1. The fresh stool can be examined immediately for the moving organisms.
2. Stool in 10% formalin can be used for Helminths and protozoa.
3. Stool in formalin-ethyl acetate is used to concentrate the stool.
4. The smallest amount of the stool needed for the examination is 2 to 5 grams.

Precautions

1. Advise patients for the following things for at least 48 hours before the collection of the stool:
   1. Avoid mineral oils.
   2. Do not take bismuth.
   3. Antibiotic s like tetracyclines.
   4. Anti-diarrheal drugs which are non-absorbent.
   5. Avoid anti-malarial drugs.
   6. The patient should not have a barium swallow examination before the stool examination.
   7. For occult blood stop iron-containing drugs, meat, and fish at least 48 hours before the collection.
2. Warm stools are better for the ova and parasites.
3. Don’t refrigerate the stool for ova and parasites.
4. Stool for ova and parasites can be collected in formalin and polyvinyl alcohol. These are used as a fixative.
5. If there is blood or mucus, that should be included in the stool. Because most of the pathogens are found in this substance.
6. Exam the stool before giving antibiotics or other drugs.
7. The semi-formed stool should be examined within 60 minutes of collection.
   1. The liquid stool should be examined within the first 30 minutes.
   2. The solid stool should be examined within the first hour of collection.
8. Trophozoites degenerate in liquid stool rapidly, so exam the stool within 30 minutes.
9. In the case of constipated cases, use non-residual purgative on the night before the collection of the stool.

Stool preservatives are:

1. Preservatives for the wet preparation are:
   1. 10% formol-saline for the wet preparation. This is the best preservatives as it kills the bacteria and preserves the protozoa and helminths.
   2. Sodium acetate formalin.
   3. Methionate iodine formalin. This is a good preservative for the field collection of the stool.
2. For staining use Polyvinyl alcohol.
3. Avoid preservatives for the culture of stool.
   1. Usually three parts of the preservatives and one part of the stool.

The normal findings in the stool:

1. Quantity
   1. The bulk of the stool is 100 to 200 grams.
   2. It may be up to 250 grams on a vegetable diet.
2. Amount of water
   1. Normally there is up to 75 % of the water in the stool.
   2. It is interesting that our body has also roughly 75% of water.
3. Gross appearance:
   1. Normal is soft and formed.
   2. Scanty mucous seen.
   3. Abundant mucous seen.
   4. Mucous with blood seen.
   5. Grossly fibrous.
   6. Homogenous appearance.
4. Color
   1. Normal color is yellowish-brown due to the presence of bilirubin and bile.
   2. In infants the color is green and the stool is loose or pasty.
   3. Various colors depending on diet.
   4. Clay color stool is seen in biliary obstruction.
   5. Tarry stool is seen if there are more than 100 ml of blood coming from the upper GI tract.
   6. The red color is seen due to blood in the large intestine, or undigested beets or tomatoes.
   7. The black color stool is seen due to blood, iron, or bismuth medication.
5. Consistency may be:
   1. Soft.
   2. Formed.
   3. Semiformed.
   4. Hard.
   5. loose.
   6. Diarrheal.
   7. Watery like a fluid.
6. pH
   1. This is from 7.0 to 7.5.
   2. This may be acidic with high lactose intake.
7. Microscopic Examination:
   1. Normally RBCs are absent.
   2. Epithelial cells are present and these are increased with GI tract irritation.
   3. Few WBCs are seen and these may be increased due to GI tract inflammation.
   4. Crystals of calcium oxalate, fatty acids, and triple phosphate are commonly present.
   5. Charcot-Leyden crystals are seen in parasitic infestation especially in amoebiasis.
   6. Undigested vegetable fibers and meat fibers are seen sometimes.
   7. Neutral fat globules, stained with Sudan may be seen normally 0 to 2 +.
   8. Hematoidin crystals are sometimes seen after GI tract hemorrhage.
      

      Stool with the presence of WBCs and RBCs

      

      Stool gross presence of blood and Mucus

8. Urobilinogen
   1. This is normally found 40 to 280 mg / 24 hours.
9. Fat
   1. Normally absent and this is less than 7 grams / 24 hours during three days period.
   2. This is less than 30% of dry weight (This is on a diet of 50 grams of fat per day).
   3. Normal
      1. 2 to 6 grams/24 hours (7 to 21 mmol/day).
10. Calcium
    1. This is about 0.6 gram / 24 hour’s.
11. Stercobilinogen normally is 40 to 280 mg/day with an average of 150 mg/day.
12. Nitrogen depends upon the nature of the diet.
    1. The normal amount is 1 to 1.5 g/day.
13. Coproporphyrin’s normal amount is 300 to 1100 µg/day.
    

    Stool normal findings

Summary of the normal stool:

Physical character	Normal values
Gross	May see vegetables, seeds, and fibers
Color	Normal = Brown Clay-colored = Biliary obstruction Red color = blood in the large intestine or undigested  beets and tomatoes Black color = Iron or bismuth medication or blood
Odor	Variable depends upon the bacterial fermentation
Consistency	Variable soft to semiformed
Amount	100 to 200 g/day
Mucous	Normally absent
Blood grossly	Negative
Parasites	Negative
Biochemical features
pH	Neutral and maybe 7.0 to 7.5
Water contents	75%
Occult blood	Negative
Reducing substances	Negative <0.25 g/dL
Porphyrins	Corporphyrins = 400 to 1200 µg/day Uroporphyrins = 10 to 14  µg/day
Neutral fat globules	Normal = 0 to 2+ seen with Sudan black stain
Urobilinogen	50 to 300 mg/day
Sodium	5.8 to 9.8 meq/day
Potassium	15.7 to 20.7 meq/day
Calcium	Roughly 0.6 gm/24 hours
Chloride	2.5 to 3.9 meq/day
Nitrogen	<2.5 g/day
Trypsin	20 to 95 U/g
Lipids (fats)	0 to 6 g/day (<7 gm/24 hours during 3 day period)
Osmolality	200 to 250 mOsm
Microscopic findings
WBCs	Negative to few Increased in GIT inflammation
RBCs	Negative
Epithelial cells	Few seen Increased in GIT irritation
Parasites	Negative
Yeast	Negative
Bacteria	Negative
Viruses	Negative
Ova and cyst	Negative
Undigested foods	Negative to a small amount
Meat fibers, starch	Negative to a small amount
Crystals	Crystals of Caoxalate, fatty acids, triple phosphate are commonly seen Crystal of hematoidin are seen after the hemorrhage Charcot’s crystals are seen after parasitic infestation, especially in amoebiasis

In routine stool examination consists of: