Examination of Stool
Stool from patient is examined to detect:
1. Adult worms
2. Segments of tapeworms
3. Ova and Cysts of Parasites
4. Larvae
5. Trophozoites
6. WBC , RBC , Pus Cells , Macrophages etc
Collection of stool sample :
1. Stool sample is to be collected in a wide mouthed leak proof container with a tight fitting lid.
2. Amount: 20 – 40 gram of solid stool or 5 – 6 tablespoonful of liquid stool .Care is to be taken to prevent contamination with urine , dirt etc .
3. Patient is to be warned not to take any medicine or medicinal substance before collection of the sample.
4. Stool sample must not be collected from bedpan containing disinfectants.
5. The container should be properly labeled with patient’s ID no., the name of the test that is desired by the clinician.
6. The stool sample is to be kept in a cool shady place but not to be frozen.
7. Stool sample is to be transported to the laboratory without any delay. Examination of stool is to be done within 30 minutes of stool sample collection (not within 30 minutes after reception of stool in the lab).
Examination of stool is divided into
a) Naked eye examination (Macroscopic Examination)
b) Chemical examination
c) Microscopic examination
a) Naked eye examination (Macroscopic Examination):
Consistency: whether the stool sample is formed, soft, loose or watery.
Presence of blood and mucus
Presence of round worm, thread worm or tapeworm proglottides
Colour and smell of stool
b) Chemical examination
Stool is usually acidic but it will be alkaline in bacillary dysentery (shigellosis).
The reaction is tested by litmus paper.
c) Microscopic examination
Two different types of slide preparations can be made for microscopic examination of stool. The saline wet mount and the Iodine wet mount. Both can be made directly from fecal specimens or from the concentrated specimens.
The saline wet mount detects worm eggs, trophozoites and cysts of protozoa, larvae of intestinal nematodes, RBCs, WBCs, etc .
The Iodine wet mount stains the nuclei and glycogen of cysts of protozoa and thus differentiates between the cysts of Entamoeba histolytica and Entamoeba coli .
Procedure
Step1: On one end of a clean glass slide, one drop of normal saline is placed and on the other end, one drop of iodine is placed.
Step 2: Using an application stick, a small portion of stool (the size of a match stick head) is placed in the saline drop and another portion is placed in the iodine drop.
Step 3: Both the drops are covered with cover slips.
Step 4: The slide is observed under microscope using 10 and 40 magnifications.
The cysts, trophozoites, ova, cells etc are identified based on their structural features .

Different Common Eggs Seen In Stool Microscopy :
Egg of Ascaris lumbricoides Egg of ( Fertilized ) Ascaris lumbricoides ( Unfertilized )

Egg of Trichuris trichiura Egg of Hook worm

Larva of Strongyloides stercorales Cyst of Giaridia intestinalis

Cyst of Entamoeba histolytica