Human feces (or faeces; Latin: fæx), also known as stool, is the waste product of the human digestive system including bacteria. It varies significantly in appearance, according to the state of the digestive system, diet and general health. Normally stool is 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.
Color variations of feces 
Human fecal matter varies significantly in appearance, depending on diet and health.
- Human feces ordinarily has a light to dark brown coloration, which results from a combination of bile and bilirubin that is derived from dead red blood cells. Normally it is semisolid, with a mucus coating.
- Yellowing of feces can be caused by an infection known as Giardiasis, which derives its name from Giardia, an anaerobic flagellated protozoan parasite that can cause severe and communicable yellow diarrhea. Another cause of yellowing is a condition known as Gilbert's Syndrome. This condition is characterized by jaundice and hyperbilirubinemia when too much bilirubin is present in the circulating blood.
- Black or red
- Feces can be black due to the presence of red blood cells that have 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 can be observed after consuming foods that contain a substantial proportion of animal blood, such as black pudding or tiết canh. Black feces can also be caused by a number of medications, such as bismuth subsalicylate (the active ingredient in Pepto-Bismol), and dietary iron supplements, or foods such as beetroot, black liquorice, or blueberries. 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. Alcoholism can also provoke abnormalities in the path of blood throughout the body, including the passing of red-black stool.
- Prussian blue, used in the treatment of radiation, cesium, and thallium poisoning, can turn the feces blue. Substantial consumption of products containing blue food dye, such as blue curaçao or grape soda, can have the same effect.
- A tarnished-silver or aluminum paint-like feces color characteristically results when biliary obstruction of any type (white stool) combines with gastrointestinal bleeding from any source (black stool). It can also suggest a carcinoma of the ampulla of Vater, which will result in gastrointestinal bleeding and biliary obstruction, resulting in silver stool. 
- Feces can be green due to having large amounts of unprocessed bile in the digestive tract. This can occasionally be the result from eating liquorice candy, as it is typically made with anise oil rather than liquorice herb and is predominantly sugar. Excessive sugar consumption or a sensitivity to anise oil may cause loose, green stools.
Feces possess physiological odor, which can vary according to diet (especially the amount of meat protein e.g., methionine) and health status. The odor of human feces is suggested to be made up from the following odorant volatiles:
- Methyl sulfides
- Benzopyrrole volatiles
- Hydrogen sulfide (H2S)
- Celiac disease
- Crohn's disease
- Ulcerative colitis.
- Chronic pancreatitis
- Cystic fibrosis
- Intestinal infection, e.g. Clostridium difficile infection.
- Short bowel syndrome
Attempts to reduce the odor of feces (and flatus) are largely based on animal research carried out with industrial applications, such as reduced environmental impact of pig farming. See also: Flatulence#Management, odor. Many dietary modifications/supplements have been researched, including:
- Activated charcoal. (Note this study concluded activated charcoal at a dose of 0.52g four times a day did not appreciably influence the liberation of fecal gases).
- Bismuth subsalicylate.
- Herbs such as rosemary
- Yucca schidigera.
- Zinc acetate.
Personal hygiene 
Cultures employ a variety of personal cleansing practising after elimination.
- In Western and East Asian societies, the use of toilet paper is widespread. Other paper products were also used before the advent of flush toilets.
- Some European countries use a bidet for additional cleaning.
- In South Asia and Southeast Asia, handheld bidets are provided for use in toilets.
- In Islam, washing of the anus with water using the left hand is part of the prescribed ritual ablutions.
- In India, the anus is also washed with water using the left hand.
- In the United Kingdom, the Indian toilet was adapted as the "WC" (water closet) and widely deployed in England during the reign of Queen Victoria. London suffered numerous outbreaks of food poisoning resulting from workers handling food after using the toilet. Cleansing of the anus was an arbitrary practice left to personal choice and facilities available.
- In Ancient Rome, a communal sponge was employed. It was rinsed in a bucket of salt water after use.
- In Japan, flat sticks were used in ancient times, being replaced by toilet paper as the country became more Westernized. Toilets that include built-in bidets have now become widely popular in private homes; these can be very sophisticated appliances, allowing users to adjust the temperature, direction and force of water jets, and offering warm air to dry the anus and surrounding regions. The toilet flushes automatically when the buttocks leave the seat.
Bristol stool scale 
The 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:
- Separate hard lumps, like nuts (hard to pass)
- Sausage-shaped but lumpy
- Like a sausage but with cracks on the surface
- Like a sausage or snake, smooth and soft
- Soft blobs with clear-cut edges
- Fluffy pieces with ragged edges, a mushy stool
- Watery, no solid pieces. Entirely Liquid
Fecal markers 
The feces can be analyzed for various markers that are indicative of various diseases and conditions. For example, fecal calprotectin levels indicate an inflammatory process such as Crohn's disease, ulcerative colitis and neoplasms (cancer).
|Reference ranges for fecal markers|
|Marker||Patient type||Upper limit||Unit|
|Calprotectin||2–9 years||166||µg/g of feces|
|≥ 60 years||112|
|≥ 10 years||4.6|
Stool analysis (stool sample) 
The main pathogens that are commonly looked for in feces include:
- Bacteroides species
- Salmonella and Shigella
- Yersinia tends to be incubated at 30 °C (86 °F), which is cooler than usual
- Campylobacter incubated at 42 °C (108 °F), in a special environment
- Candida if the person is immunosuppressed (e.g., undergoing cancer treatment)
- E. coli O157 if blood is visible in the stool sample
- Entamoeba histolytica
Undigested food remnants 
Diarrhea is the condition of having three or more loose or liquid bowel movements per day. This condition can be a symptom of injury, disease or foodborne illness and is usually accompanied by abdominal pain, and often nausea and vomiting. There are other conditions which involve some but not all of the symptoms of diarrhea, and so the formal medical definition of diarrhea involves defecation of more than 200 grams per day (though formal weighing of stools to determine a diagnosis is never actually carried out).
It occurs when insufficient fluid is absorbed by the colon. As part of the digestion process, or due to fluid intake, food is mixed with large amounts of water. Thus, digested food is essentially liquid prior to reaching the colon. The colon absorbs water, leaving the remaining material as a semisolid stool. If the colon is damaged or inflamed, however, absorption is inhibited, and watery stools result.
Diarrhea is most commonly caused by myriad viral infections but is also often the result of bacterial toxins and sometimes even infection. In sanitary living conditions and with ample food and water available, an otherwise healthy patient typically recovers from the common viral infections in a few days and at most a week. However, for ill or malnourished individuals diarrhea can lead to severe dehydration and can become life-threatening without treatment.
|This section requires expansion. (September 2012)|
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 (109 °F) overnight. Although most strains of E. coli are harmless, their presence is indicative of fecal contamination, and hence an increased possibility of the presence of more dangerous organisms.
Fecal contamination of water sources is highly prevalent worldwide, accounting for the majority of unsafe drinking water. 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.
See also 
- Sometimes but not always stools in UK English; plural use not even mentioned in Oxford online dictionaries
- Heller, JL (2009-11-01). "Bloody or tarry stools". National Institutes of Health. Retrieved 2009-11-30.
- "Fact Sheet: Prussian Blue". Centers for Disease Control and Prevention. 2006-05-10. Retrieved 2009-11-30.
- Hiele, M; Ghoos, Y; Rutgeerts, P; Vantrappen, G; Schoorens, D (1991 Jun). "Influence of nutritional substrates on the formation of volatiles by the fecal flora.". Gastroenterology 100 (6): 1597–602. PMID 2019366.
- Tangerman, A (2009 Oct 15). "Measurement and biological significance of the volatile sulfur compounds hydrogen sulfide, methanethiol and dimethyl sulfide in various biological matrices.". Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 877 (28): 3366–77. PMID 19505855.
- Chavez, C; Coufal, CD; Carey, JB; Lacey, RE; Beier, RC; Zahn, JA (2004 Jun). "The impact of supplemental dietary methionine sources on volatile compound concentrations in broiler excreta.". Poultry science 83 (6): 901–10. PMID 15206616.
- Geypens, B; Claus, D; Evenepoel, P; Hiele, M; Maes, B; Peeters, M; Rutgeerts, P; Ghoos, Y (1997 Jul). "Influence of dietary protein supplements on the formation of bacterial metabolites in the colon.". Gut 41 (1): 70–6. PMID 9274475.
- Otto, ER; Yokoyama, M; Hengemuehle, S; von Bermuth, RD; van Kempen, T; Trottier, NL (2003 Jul). "Ammonia, volatile fatty acids, phenolics, and odor offensiveness in manure from growing pigs fed diets reduced in protein concentration.". Journal of animal science 81 (7): 1754–63. PMID 12854812.
- Dugdale, David C. ""Stools - foul smelling" on Medline Plus". U.S. National Library of Medicine. Retrieved 21 October 2012.
- Levine, J; Ellis, CJ; Furne, JK; Springfield, J; Levitt, MD (1998 Jan). "Fecal hydrogen sulfide production in ulcerative colitis.". The American journal of gastroenterology 93 (1): 83–7. PMID 9448181.
- Bartlett, John G.; Gerding, Dale N. (15 January 2008). "Clinical Recognition and Diagnosis of Infection". Clinical Infectious Diseases 46 (s1): S12–S18. doi:10.1086/521863.
- Suarez, FL; Furne, J; Springfield, J; Levitt, MD (1999 Jan). "Failure of activated charcoal to reduce the release of gases produced by the colonic flora.". The American journal of gastroenterology 94 (1): 208–12. PMID 9934757.
- Suarez, FL; Furne, JK; Springfield, J; Levitt, MD (1998 May). "Bismuth subsalicylate markedly decreases hydrogen sulfide release in the human colon.". Gastroenterology 114 (5): 923–9. PMID 9558280.
- Giffard, CJ; Collins, SB; Stoodley, NC; Butterwick, RF; Batt, RM (2001 Mar 15). "Administration of charcoal, Yucca schidigera, and zinc acetate to reduce malodorous flatulence in dogs.". Journal of the American Veterinary Medical Association 218 (6): 892–6. PMID 11294313.
- Lewis SJ, Heaton KW (1997). "Stool form scale as a useful guide to intestinal transit time". Scand. J. Gastroenterol. 32 (9): 920–4. doi:10.3109/00365529709011203. PMID 9299672.
- "Constipation Management and Nurse Prescribing: The importance of developing a concordant approach" (PDF). Archived from the original on 2006-07-05. Retrieved 2006-11-06.
- Joshi, S.; Lewis, S. J.; Creanor, S.; Ayling, R. M. (2009). "Age-related faecal calprotectin, lactoferrin and tumour M2-PK concentrations in healthy volunteers". Annals of Clinical Biochemistry 47 (Pt 3): 259–263. doi:10.1258/acb.2009.009061. PMID 19740914.
- "Diarrhoea". World Health Organization.
||This article needs additional citations for verification. (January 2008)|
- Media related to Human feces at Wikimedia Commons