STOOL
EXAMINATION
COLLECTI
ON
• Universal precautions
• Pt. is asked to pass stool in a clean container.
• Stool should be collected in a steralized, wide mouthed container.
• Loose/last/portion containing mucus, blood etc is to be collected in a wide
mouthed bottle.
• Should be uncontaminated with urine or any other body secretions.
• >2gm is required.
• Properly named and always a fresh sample should be tested.
• Liquid stool to be examined within ½ hour
• Solid stool to be examined within 1 hour.
• If delayed store in a refrigerator.
COLLECTION
CONTD...
• 3 samples of stool within 10 days to exclude false negatives.
• 2 samples to be examined on alternate days after normal
defaecation and 1 sample after a purgative for certain worms.
• Formalin is the best preservative. It kills the bacteria but
ptreserves the protozoa and helminthes.
• For culture no preservatives to be used
Eggs of Pin worm –
Enterobius vermicularis rarely appear in stools.
PINWORM ( These are usually collected in the folds of skin
in perianal region.
ENTEROBIUS)
EGG • COLLECTION: Cotton swab / Plaster patch –
COLLECTIONAnus especially in early morning – Dipped in
Saline – Observed.
TYPES OF
EXAMINATION
• PHYSICAL EXAMINATION: colour, volume, consistency, odour,
mucus, pus, blood, helminths.
• CHEMICAL EXAMINATION: reactions, occult blood, fat,
carbohydrate, etc
• MICROSCOPIC EXAMINATION: remnants of food, crystals, pus
cells, macrophages, RBCs, bacteria, yeasts, molds, protozoa, helminths.
• STOOL CULTURE:
Physical examination
RECORD FOLLOWING FINDINGS:
• AMOUNT
• CONSISTENCY
• COLOUR
• ODOUR
• MUCUS
• BLOOD
• PUS
Chemical Examination Of
Stool
RECORD FOLLOWING FINDINGS:
• Acidity/basicity (pH)
• Fats
• Occult blood
• Reducing substances
Occult
blood
• Detect blood which is present in amount or form not visible
macroscopically
• Normally nil
• Abnormal presence in condition of occult haemorrhage in the GI
tract
• BENZIDINE TEST
• GUAIAC TEST
• ORTHOTOLUIDINE TEST
Most commonly used test is benzidine test
BENZIDINE TEST
• 4 gm benzidine in 100 ml of glacial acetic acid
• Emulsify pea sized bit of faeces in 5 ml of water.
• Mix 1 ml emulsion and 1 ml of reagent in test tube
• Add several drops of 35 H2O2
• Blue colour indicates positive reaction
MICROSCOPIC
EXAMINATION
NEED FOR MICROSCOPIC
EXAMINATION
• For the diagnosis of microscopic elements.
• Trophozoites and its movements are better seen in unstained
preparation of a fresh material.
• Cystic forms &Nuclear character are better seen in stained
preparation(iodine)
• Gycogen mass- stained with iodine
• Chromatoid bars- unstained preparation
FLOATATION TECHNIQUE
• Use solutions which have highier specific gravity(zinc sulphate or
Sheather’s sugar) than the organisms to be floated so that the
organisms rise to the top and the debries sink to the bottom.
• Advantage – produce a cleaner material than the sedimentation
technique
• Disadvantage – walls of eggs and cyst will often collapse,
hindering identification.
• Some parasite eggs do not float.
SEDIMETATION TECHNIQUE
• Use solutions of lower specific gravity
than the parasitic organisms(formalin
ethyl acetate technique)
• Recommended for general diagnostic
laboratories due to easy to perform and
less prone to technical error.
Staining methods
• Wet mount
• normal saline
• Iodine solution
• Buffered methylene blue solution
Microscopic examination of wet mount
Saline wet mount
Iodine wet mount
• Iodine kills the organisms, therefore motility is lost.
• Used mainly to stain nuclei and glycogen mass if present.
• Flagella becomes recognisable.
• Cyst can usually be specifically identified in this method.
• Lugol’s iodine solution is used.
Buffered methylene blue wet mount
• Stains only trophozoites of amoeba
• It does not stain amoebic cyst or
trophozoites and cyst of flagellates.
• Nucleus and the inclusions such as RBC or
yeast cells stain dark blue
• Cytoplasm stains light blue
Vegetable cell
• Sometimes causes
confusion with ova, eggs,
cyst or cell bodies
• IRREGULAR OUTER
MARGIN
• Excess quantity is seen in
excess intake of vegetables
or indigestion
Fat globules
• Appear similar to parasitic
cyst or cell bodies
• Emulsifying agents are used
to eliminate confusion
• Confused with ova of
helminths
• Found in fat dyspepsia
Epithelial cells
• Excess presence
due to
inflammatory
conditions of
colon, rectum, anal
canal
Pus cells
• Commonly found in normal
stool, help to ease the passage of
stool
• Normally not visible to human
eye.
• If visible indicates disease
• Bacillary dysentery, UC, acute
Amoebic dysentery, malignancy
of rectum, drug induced
enterocilitis
RBCs
• seen in cases of
ulcrative lesions of
gut
• in bacillary dysentery
– yellowish discrete
• Amoebic dysentery –
greenish and in
clumps
Crystals
• Fatty acid crystals
• Calcium oxalate crystals
• Triple phosphate crystals
• Charcot Leyden crystals
• Haemotoidin crystals
• Crystals of drugs
Charcot Leyden crystal:
• Slender and pointed at both ends,
Hexagonal bipyramidal structures
localised in the primary granules of
cytoplasm of eosinophils and basophils
• Evidence of parasitic infiltrate eg amoeba,
ascaris, hookworm, fasciola
• diamond shaped or whetstone shaped
crystals
• Normally colourless, stained purplish- red
by trichome
• Vary in size and may be as large as 50 µm
in length
• Found in UC, dysentery, malignant ulcers,
schistosomiasis etc
Haematoidin crystals:
• Ironless pigment derived from
haemoglobin and formed within
tissues(reticuloendothelial cells) but
found extracellularly after 5-7 days in
foci of previous haemorrhage.
• Occurs as refractile, yellow- brown
and orange-red granules
Yeast and molds
• Yeast are normally
present
• Excess in cases of
AIDS
• Molds are rare but may
be seen in
immunodeficiency
conditions
HOOKWORM (Ancylostoma
duodenale)
ROUNDWORM
(Ascaris
lumbricoides)
TAPEWORM (Taenia solium-Pork
Taenia saginata-Beef)
WHIPWORM (Trichuris trichura)
PINWORM (Enterobius vermicularis)
Entamoeba histolytica
Giardia
lamblia
