Feces

Feces (also spelt faeces) is the excrement from the digestive tract expelled
from the anus of animals by defecation. It consists of water, undigested
food residues, digestive secretions, and bacteria. The reddish-brown color
of human feces is derived from stercobilin, created by bacterial action on
bilirubin and subsequent oxidation.

The word feces comes from the Latin word faex which means "dregs".

Feces are also known as scat and scatology is the study of feces.

Feces are generally a taboo subject. This is probably because of the need 
to keep feces well away from food, for health reasons.

Coprophilia is a sexual attraction to feces. Coprophagia is the extremely
hazardous practice of eating feces.

Laboratory testing of feces

In the medical profession, feces are referred to as stools. This comes from
the Anglo-Saxon word stol, which means "seat". The word stool was originally
used to describe the seat one sat on to go to the bathroom. So, the
expression was that they were "going to stool." By the end of the 16th
century, the word stool was used to mean the same thing as feces.

Feces will usually be required for microbiological testing, looking for an
intestinal pathogen.

Biochemical tests done on feces include fecal elastase and fecal fat
measurements, as well as tests for fecal occult blood.

It is recommended that the clinician correlates the symptoms and submit
specimens according to laboratory guidelines to obtain results that are
clinically significant. Formed stools often do not give satisfactory results
and suggest little of actual pathologic conditions.

Three main types of microbiological tests are commonly done on feces:

   * Antibody-antigen type tests, that look for a specific virus (e.g.
     rotavirus).
   * Microscopic examination for intestinal parasites and their ova (eggs).
   * Routine culture.

Routine culture involves streaking the sample onto agar plates containing
special additives, such as MacConkey's Agar, that will inhibit the growth of
Gram positive organisms and will selectively allow enteric pathogens to
grow, and incubating them for a period, and observing the bacterial colonies
that have grown.

Yellowing of feces can be caused by an infection known as giardia. Giardia
are tiny parasitic organisms. If giardia infects the intestines it can cause
severe yellow diarrhea. This is a dangerous communicable infection and must
be reported.

Another cause of yellowing is a condition known as Gilbert's Syndrome. This
condition is characterized by jaundice and hyperbilirubinemia.
Hyperbilirubinemia occurs when too much bilirubin is present in the
circulating blood.

Feces can be black if dried blood is present in it from a bleed. More active
bleeding can lead feces to be red in color.

In children with certain illnesses, Feces can be blue or green. Babies also
produce green feces when they are given food for the first time.

The main pathogens that are commonly looked for in feces include:

   * Salmonella and Shigella
   * Yersinia (this tends to be incubated at 30¡C, which is cooler than
     usual.)
   * Campylobacter (incubated at 42¡C, in a special environment.)
   * Aeromonas
   * Candida (if the person is immunosupressed e.g. cancer treatment.)
   * E. coli O157 (if blood is visible in the stool sample.)