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Sample 

  1. 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 antibiotic or other drugs.
  7. Semi-formed stool should be examined within 60 minutes of collection.
    1. Liquid stool should be examined within the first 30 minutes.
    2. 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 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:

Summary of the normal Stool:

Physical character Normal values
Gross May see vegetables, seeds, and fibers
Color Brown
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
Urobilinogen 50 to 300 mg/day 
Sodium 5.8 to 9.8 meq/day
Potassium 15.7 to 20.7 meq/day
Chloride 2.5 to 3.9 meq/day
Nitrogen <2.5 g/day
Trypsin 20 to 95 U/g
Lipids  0 to 6 g/day
Osmolality 200 to 250 mOsm
Microscopic findings  
WBCs Negative
RBCs Negative
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

Possible References Used

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