Human feces

Human Feces (also faeces &mdash; see spelling differences), also known as stools, is the waste product of the human digestive system and varies significantly in appearance, depending on the state of the whole digestive system, influenced by diet and health. Normally stools are semisolid, with a mucus coating. Small pieces of harder, less moist feces can sometimes be seen impacted on the distal (leading) end. This is a normal occurrence when a prior bowel movement is incomplete; and feces are returned from the rectum to the intestine, where water is absorbed. Meconium (sometimes erroneously spelled merconium) is a newborn baby's first feces. Human feces are a defining subject of toilet humor.

Fecal management
The management of feces is an issue of hygiene, since feces contribute to spreading of diseases and intestinal parasites. The problem of efficient management of feces has existed since the times when people started to live in permanent settlements, primarily for the reasons of cleanliness and odour. Toilets were known in ancient India (dated as early as 2,500 BC), in Ancient Rome, Egypt and China, although the contemporary flush toilet originated in 19th century Victorian England.

Until the end of the 19th century, the primary concern of sewage collection and disposal in the Western world was to remove waste away from inhabited places, and it was common to use waterflows and larger bodies of water as a destination of sewage, where waste could be naturally dissipated and neutralized. With the increased population density this is no longer a viable solution, and special processing of sewage is required. The lack of the latter is a grave sanitary and public health problem in developing countries.

It is thought one human's annual excrement is the equivalent of 25 kg of commercially produced 20:10:10 NPK fertiliser.

Laboratory testing of feces
Feces will sometimes be required for microbiological testing, looking for an intestinal pathogen or other parasite or disease.

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 correlate 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 pathological 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 agar, that will inhibit the growth of Gram-positive, thick membranes organisms and will selectively allow enteric pathogens to grow, and incubating them for a period, and observing the bacterial colonies that have grown.

Bristol Stool Chart


The Bristol Stool Chart or Bristol Stool Scale is a medical aid designed to classify the form of human feces into seven categories. Sometimes referred to in the UK as the "Meyers Scale," it was developed by K.W.Heaton at the University of Bristol and was first published in the Scandinavian Journal of Gastroenterology in 1997. The form of the stool depends on the time it spends in the colon.

The seven types of stool are:
 * Type 1: Separate hard lumps, like nuts (hard to pass)
 * Type 2: Sausage-shaped, but lumpy
 * Type 3: Like a sausage but with cracks on its surface
 * Type 4: Like a sausage or snake, smooth and soft
 * Type 5: Soft blobs with clear cut edges (passed easily)
 * Type 6: Fluffy pieces with ragged edges, a mushy stool
 * Type 7: Entirely liquid

Types 1 and 2 indicate constipation, with 3 and 4 being the "ideal stools" especially the latter, as they are the easiest to pass, and 5–7 being further tending towards diarrhea or urgency.

Color variations of feces
Yellowing of feces can be caused by an infection known as Giardiasis, which derives its name from Giardia, a microscopic parasitic organism. 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 due to the presence of blood that has been in the intestines long enough to be broken down by digestive enzymes. This is known as melena, and is typically due to bleeding in the upper digestive tract, such as from a bleeding peptic ulcer. The same color change (albeit harmless) can be observed after consuming foods that contain substantial proportion of animal bloods, such as Black pudding or Tiết canh. The black color is caused by oxidation of the iron in the blood's hemoglobin. Black feces can also be caused by a number of medications, such as bismuth subsalicylate, and dietary iron supplements. Because liquorice is high in iron, this may also cause the feces to become black. Hematochezia is similarly the passage of feces that are bright red due to the presence of undigested blood, either from lower in the digestive tract, or from a more active source in the upper digestive tract.

In children with certain illnesses, feces can be blue or green. Eating green or leafy food can turn feces green. Babies when digesting solid food for the first time also produce feces which tend to be green and of unusual consistency because of the presence of cells discarded during development of the digestive tract. Food with large amounts of food color can cause feces to be colored. An example is FDA Blue #5, which turns feces green when it reacts with bile in the intestine. The effect is considered harmless, and there have been no reports of ill effects. After a barium meal, the subsequent stool should be white.

Fecal contamination
A quick test for fecal contamination of water sources or soil is a check for the presence of E. coli bacteria performed with the help of MacConkey agar plates or Petri dishes. E. coli bacteria uniquely develop red colonies at temperature of approximately 43 °C overnight. While most strains of E. coli are harmless, their presence is indicative of more serious fecal contamination, and hence a high possibility of more dangerous organisms.

Fecal contamination of water sources is highly prevalent worldwide, accounting for the majority of unsafe drinking water, which is the only water available to 1.1 billion people. In developing countries most sewage is discharged without treatment. Even in developed countries events of sanitary sewer overflow are not uncommon and regularly pollute the Seine River (France) and the River Thames (England), for example.

The main pathogens that are commonly looked for in feces include:
 * Salmonella and Shigella
 * Yersinia 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 immunosuppressed e.g. cancer treatment
 * E. coli O157 if blood is visible in the stool sample
 * Cryptosporidium
 * Entamoeba histolytica

Tourism
Nature reserve organizations, parks, and tourist agencies often issue regulations for tourists aimed at the prevention of the pollution of nature. In particular, catholes (cat holes), i.e., pits for feces, must be located at a reasonable distance (at least 60 m) from water sources (rivers, lakes, etc.), to avoid possible bacterial contamination of water via precipitation, as well as away from trails. For faster feces decomposition, organic soil is preferred over sandy mineral soil. It is also recommended to avoid concentration of catholes around campsites. Filled catholes must be covered with a reasonably thick layer of soil, to prevent access by animals, some of which are coprophagous.

Some areas require special instructions of human waste disposal. In rocky places, with the absence of soil, it is advised to spread feces thinly by smearing over rocks with good sun access for faster sterilization by UV radiation and drying. In larger snow fields, a larger distance (e.g., 200 m) from trails and campsites may be mandated, if the waste is being disposed under snow.