Faeces Examination

Collection of sample - The sample of faeces is preferably collected in a disposable cardboard container. Examination should be delayed for more than a few hours especially when amoebae are to be looked for.

Naked eye examination

• Quantity - Bacteria usually make up one third to one half of the dry weight of faeces. Bulkier stools occur with vegeterian diet.

• Colour - Normal faeces are light to dark brown in colour due to the presence of bile pigments. Coloured stools occur in obstructive jaundice due to absence of bile pigments in the stool.Tarry or black stools occur in upper gastrointestinal haemorrhage due to altered blood. Tarry stools also occur following iron administration.

• Consistency - Normal stools are well formed. Watery stools occur in diarrhoea.Hard faeces suggest constipation. Flattened and ribbon like stools occur in obstruction in the lumen of the bowels. Palel, bulky, semi-solid, frothy stools, occur in malabsorption syndrome.

• Odour - Normal odour of the faeces is due to presence of indole and skatole, which is stronger than after a meat diet. In nursing infants a typical sour odour due to the presence of fatty acids occurs.

• Blood and Mucus - Small amounts of mucus may be normally present. When large amount of mucus is present, especially with blood, it suggests lesions of the large gut especially amoebic or bacillary dysentery.

• Parasites - Stools may contain worms or segments of worms eg.roundworm, tapeworm etc.

Chemical examination

• Reaction - Normal stools are slightly acidic or slightly alkaline.

• Benzidine tests are done for occult blood.

Microscopic examination

• Saline preparation - A bit of faecal matter is taken on the end of narrow stick and a thin emulsion in a drop of saline is prepared on the slide. A cover slip is put and the smear is examined to detect the motility of E.histolytica and other organisms.
• Iodine preparation - This is done in a similar manner as saline preparation except that instead of saline, Gram's iodine is used. Iodine stains nuclear structures making identification simpler. However, this preparation kills the organisms and hence motility cannot be detected.
• Hanging drop preparation - A bit of diluted faecal material is taken on a coverslip which is inverted on a special slide and then examined under the microscope. This helps to examine the darting motility of Vibrio cholera.