Editing Diarrhea (section)

==Causes==
[[File:Stomach colon rectum diagram-en.svg|right|thumb|Diagram of the [[human gastrointestinal tract]]]]

In the latter stages of human digestion, ingested materials are inundated with water and digestive fluids such as [[gastric acid]], [[bile]], and [[digestive enzyme]]s in order to break them down into their nutrient components, which are then absorbed into the bloodstream via the [[Intestinal epithelium|intestinal tract]] in the small intestine. Prior to defecation, the large intestine reabsorbs the water and other digestive solvents in the waste product in order to maintain proper hydration and overall equilibrium.<ref>{{cite book| vauthors = Maton A, Hopkins J, McLaughlin CM, Johnson S, Warner MQ, LaHart D, Wright JD | title = Human Biology and Health| publisher = Prentice Hall| year = 1993| location = Englewood Cliffs, NJ| isbn = 978-0-13-981176-0| oclc = 32308337| url-access = registration| url = https://archive.org/details/humanbiologyheal00scho}}</ref> Diarrhea occurs when the large intestine is prevented, for any number of reasons, from sufficiently absorbing the water or other digestive fluids from fecal matter, resulting in a liquid, or "loose", bowel movement.<ref>{{Cite web |title=Diarrhea: Types, Causes, Complications & Treatment |url=https://my.clevelandclinic.org/health/diseases/4108-diarrhea |access-date=2022-07-19 |website=Cleveland Clinic |archive-date=19 July 2022 |archive-url=https://web.archive.org/web/20220719133818/https://my.clevelandclinic.org/health/diseases/4108-diarrhea |url-status=live }}</ref>

[[acute (medicine)|Acute]] diarrhea is most commonly due to viral [[gastroenteritis]] with [[rotavirus]], which accounts for 40% of cases in children under five.<ref name=WHO2010a/> In [[traveler's diarrhea|travelers]], however, [[bacterial infections]] predominate.<ref name="pmid16267716"/> Various toxins such as [[Amanita phalloides#Signs and symptoms|mushroom poisoning]] and drugs can also cause acute diarrhea.

Chronic diarrhea can be the part of the presentations of a number of chronic medical conditions affecting the intestine. Common causes include [[ulcerative colitis]], [[Crohn's disease]], [[microscopic colitis]], [[celiac disease]], [[irritable bowel syndrome]], and [[bile acid malabsorption]].<ref>{{Cite web |title=Microscopic colitis - Symptoms and causes |url=https://www.mayoclinic.org/diseases-conditions/microscopic-colitis/symptoms-causes/syc-20351478 |access-date=2022-07-19 |website=Mayo Clinic |language=en |archive-date=3 April 2022 |archive-url=https://web.archive.org/web/20220403123231/https://www.mayoclinic.org/diseases-conditions/microscopic-colitis/symptoms-causes/syc-20351478 |url-status=live }}</ref>

===Infections===
{{Main|Infectious diarrhea}}

There are many causes of infectious diarrhea, which include [[virus]]es, [[bacteria]] and parasites.<ref name="pmid18813221">{{cite journal | vauthors = Navaneethan U, Giannella RA | s2cid = 34096072 | title = Mechanisms of infectious diarrhea | journal = Nature Clinical Practice. Gastroenterology & Hepatology | volume = 5 | issue = 11 | pages = 637–47 | date = November 2008 | pmid = 18813221 | doi = 10.1038/ncpgasthep1264 }}</ref> Infectious diarrhea is frequently referred to as [[gastroenteritis]].<ref name=Dav2008>{{cite book|vauthors=Schlossberg D|title=Clinical Infectious Disease|date=2008|publisher=Cambridge University Press|isbn=978-1-139-57665-9|page=349|url=https://books.google.com/books?id=-wWY1_mSeq0C&pg=PA349|access-date=9 September 2017|archive-date=14 January 2023|archive-url=https://web.archive.org/web/20230114192338/https://books.google.com/books?id=-wWY1_mSeq0C&pg=PA349|url-status=live}}</ref> [[Norovirus]] is the most common cause of viral diarrhea in adults,<ref name="pmid19084472">{{cite journal | vauthors = Patel MM, Hall AJ, Vinjé J, Parashar UD | title = Noroviruses: a comprehensive review | journal = Journal of Clinical Virology | volume = 44 | issue = 1 | pages = 1–8 | date = January 2009 | pmid = 19084472 | doi = 10.1016/j.jcv.2008.10.009 }}</ref> but [[rotavirus]] is the most common cause in children under five years old.<ref name="pmid19457420">{{cite journal | vauthors = Greenberg HB, Estes MK | title = Rotaviruses: from pathogenesis to vaccination | journal = Gastroenterology | volume = 136 | issue = 6 | pages = 1939–51 | date = May 2009 | pmid = 19457420 | pmc = 3690811 | doi = 10.1053/j.gastro.2009.02.076 }}</ref> [[Adenovirus]] types 40 and 41,<ref name="pmid1962727">{{cite journal | vauthors = Uhnoo I, Svensson L, Wadell G | title = Enteric adenoviruses | journal = Baillière's Clinical Gastroenterology | volume = 4 | issue = 3 | pages = 627–42 | date = September 1990 | pmid = 1962727 | doi = 10.1016/0950-3528(90)90053-J }}</ref> and [[astrovirus]]es cause a significant number of infections.<ref name="pmid12442031">{{cite journal | vauthors = Mitchell DK | title = Astrovirus gastroenteritis | journal = The Pediatric Infectious Disease Journal | volume = 21 | issue = 11 | pages = 1067–9 | date = November 2002 | pmid = 12442031 | doi = 10.1097/00006454-200211000-00018 | s2cid = 3177998 }}</ref> [[Shiga-toxin producing Escherichia coli]], such as [[E coli o157:h7]], are the most common cause of infectious bloody diarrhea in the United States.<ref>{{Citation |last1=Akhondi |first1=Hossein |title=Bacterial Diarrhea |date=2022 |url=http://www.ncbi.nlm.nih.gov/books/NBK551643/ |work=StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=31869107 |access-date=2022-07-19 |last2=Simonsen |first2=Kari A. |archive-date=15 June 2022 |archive-url=https://web.archive.org/web/20220615215551/https://www.ncbi.nlm.nih.gov/books/NBK551643/ |url-status=live }}</ref>

''[[Campylobacter]]'' [[species|spp.]] are a common cause of bacterial diarrhea, but infections by ''[[Salmonella]]'' spp., ''[[Shigella]]'' spp. and some strains of ''Escherichia coli'' are also a frequent cause.<ref name="pmid19116615">{{cite journal | vauthors = Viswanathan VK, Hodges K, Hecht G | title = Enteric infection meets intestinal function: how bacterial pathogens cause diarrhoea | journal = Nature Reviews. Microbiology | volume = 7 | issue = 2 | pages = 110–9 | date = February 2009 | pmid = 19116615 | pmc = 3326399 | doi = 10.1038/nrmicro2053 }}</ref>

In the elderly, particularly those who have been treated with antibiotics for unrelated infections, a toxin produced by ''[[Clostridioides difficile (bacteria)|Clostridioides difficile]]'' often causes severe diarrhea.<ref name="pmid19528959">{{cite journal | vauthors = Rupnik M, Wilcox MH, Gerding DN | s2cid = 23376891 | title = Clostridium difficile infection: new developments in epidemiology and pathogenesis | journal = Nature Reviews. Microbiology | volume = 7 | issue = 7 | pages = 526–36 | date = July 2009 | pmid = 19528959 | doi = 10.1038/nrmicro2164 }}</ref>

Parasites, particularly [[protozoa]] e.g., ''[[Cryptosporidium]]'' spp., ''[[Giardia]]'' spp., ''[[Entamoeba histolytica]]'', ''[[Blastocystis]]'' spp., ''[[Cyclospora cayetanensis]]'', are frequently the cause of diarrhea that involves chronic infection. The broad-spectrum antiparasitic agent [[nitazoxanide]] has shown efficacy against many diarrhea-causing parasites.<ref name="pmid22301075">{{cite journal | vauthors = Rossignol JF, Lopez-Chegne N, Julcamoro LM, Carrion ME, Bardin MC | title = Nitazoxanide for the empiric treatment of pediatric infectious diarrhea | journal = Transactions of the Royal Society of Tropical Medicine and Hygiene | volume = 106 | issue = 3 | pages = 167–73 | date = March 2012 | pmid = 22301075 | doi = 10.1016/j.trstmh.2011.11.007 }}</ref>

Other infectious agents, such as [[parasites]] or [[bacteria]]l toxins, may exacerbate symptoms.<ref name="pmid16267716">{{cite journal | vauthors = Wilson ME | title = Diarrhea in nontravelers: risk and etiology | journal = Clinical Infectious Diseases | volume = 41 | issue = Suppl 8 | pages = S541-6 | date = December 2005 | pmid = 16267716 | doi = 10.1086/432949 | series = 41 | doi-access = free }}</ref> In sanitary living conditions where there is ample food and a supply of clean water, an otherwise healthy person usually recovers from viral infections in a few days. However, for ill or [[malnourished]] individuals, diarrhea can lead to severe [[dehydration]] and can become life-threatening.<ref name="pmid12608880">{{cite journal | vauthors = Alam NH, Ashraf H | s2cid = 26076784 | title = Treatment of infectious diarrhea in children | journal = Paediatric Drugs | volume = 5 | issue = 3 | pages = 151–65 | year = 2003 | pmid = 12608880 | doi = 10.2165/00128072-200305030-00002 | doi-access = free }}</ref>

====Sanitation====
[[File:Slum and dirty river.jpg|thumb|Poverty often leads to unhygienic living conditions, as in this community in the Indian Himalayas. Such conditions promote contraction of diarrheal diseases, as a result of poor [[sanitation]] and [[hygiene]].]]
[[Open defecation]] is a leading cause of infectious diarrhea leading to death.<ref>{{cite web |url=https://www.who.int/mediacentre/factsheets/fs330/en/ |title=WHO &#124; Diarrhoeal disease |publisher=Who.int |access-date=10 March 2014 |url-status=live |archive-url=https://web.archive.org/web/20140401193648/http://www.who.int/mediacentre/factsheets/fs330/en/ |archive-date=1 April 2014 }}</ref>

Poverty is a good indicator of the rate of infectious diarrhea in a population. This association does not stem from poverty itself, but rather from the conditions under which impoverished people live. The absence of certain resources compromises the ability of the poor to defend themselves against infectious diarrhea. "Poverty is associated with poor housing, crowding, dirt floors, lack of access to clean water or to sanitary disposal of fecal waste ([[sanitation]]), cohabitation with domestic animals that may carry human pathogens, and a lack of refrigerated storage for food, all of which increase the frequency of diarrhea{{nbsp}}... Poverty also restricts the ability to provide age-appropriate, nutritionally balanced diets or to modify diets when diarrhea develops so as to mitigate and repair nutrient losses. The impact is exacerbated by the lack of adequate, available, and affordable medical care."<ref>{{cite book| vauthors = Jamison DT |title=Disease control priorities in developing countries|date=2006|publisher=Oxford Univ. Press|location=New York|isbn=978-0-8213-6179-5 |edition=2nd}}</ref>

One of the most common causes of infectious diarrhea is a lack of clean water. Often, improper fecal disposal leads to contamination of groundwater. This can lead to widespread infection among a population, especially in the absence of water filtration or purification. Human feces contains a variety of potentially harmful human [[pathogens]].<ref name="Brown 629–34">{{cite journal | vauthors = Brown J, Cairncross S, Ensink JH | title = Water, sanitation, hygiene and enteric infections in children | journal = Archives of Disease in Childhood | volume = 98 | issue = 8 | pages = 629–34 | date = August 2013 | pmid = 23761692 | pmc = 3717778 | doi = 10.1136/archdischild-2011-301528 }}</ref>

====Nutrition====
Proper nutrition is important for health and functioning, including the prevention of infectious diarrhea. It is especially important to young children who do not have a fully developed immune system. [[Zinc deficiency]], a condition often found in children in [[developing countries]] can, even in mild cases, have a significant impact on the development and proper functioning of the human immune system.<ref>{{cite journal|vauthors=Black RE, Sazawal S|title=Zinc and childhood infectious disease morbidity and mortality|journal=The British Journal of Nutrition|volume=85|pages=S125-9|date=May 2001|issue=Suppl 2|pmid=11509100|doi=10.1079/bjn2000304|doi-access=free}}</ref><ref>{{cite journal|vauthors=Shankar AH, Prasad AS|title=Zinc and immune function: the biological basis of altered resistance to infection|journal=The American Journal of Clinical Nutrition|volume=68|issue=2 Suppl|pages=447S–463S|date=August 1998|pmid=9701160|doi=10.1093/ajcn/68.2.447S|doi-access=free}}</ref> Indeed, this relationship between zinc deficiency and reduced immune functioning corresponds with an increased severity of infectious diarrhea. Children who have lowered levels of zinc have a greater number of instances of diarrhea, severe diarrhea, and diarrhea associated with fever.<ref>{{cite journal|vauthors=Bahl R, Bhandari N, Hambidge KM, Bhan MK|title=Plasma zinc as a predictor of diarrheal and respiratory morbidity in children in an urban slum setting|journal=The American Journal of Clinical Nutrition|volume=68|issue=2 Suppl|pages=414S–417S|date=August 1998|pmid=9701154|doi=10.1093/ajcn/68.2.414S|doi-access=free}}</ref> Similarly, [[vitamin A deficiency]] can cause an increase in the severity of diarrheal episodes. However, there is some discrepancy when it comes to the impact of vitamin A deficiency on the rate of disease. While some argue that a relationship does not exist between the rate of disease and vitamin A status,<ref>{{cite book|vauthors=Rice AL, West KP, Black RE|chapter=Vitamin A deficiency|veditors=Ezzati M, Lopez AD, Rodgers A, Murray CJ|title=Comparative quantification of health risks: global and regional burden of disease attributes to selected major risk factors.|location=Geneva|publisher=World Health Organization|year=2004|volume=1|pages=211–56, especially 238–240|chapter-url=http://apps.who.int/iris/bitstream/handle/10665/42792/9241580348_eng_Volume1.pdf|access-date=30 December 2018|archive-date=31 July 2020|archive-url=https://web.archive.org/web/20200731084243/https://apps.who.int/iris/bitstream/handle/10665/42792/9241580348_eng_Volume1.pdf|url-status=live}}</ref> others suggest an increase in the rate associated with deficiency.<ref>{{cite journal|vauthors=Sommer A, Katz J, Tarwotjo I|title=Increased risk of respiratory disease and diarrhea in children with preexisting mild vitamin A deficiency|journal=The American Journal of Clinical Nutrition|volume=40|issue=5|pages=1090–5|date=November 1984|pmid=6496388|doi=10.1093/ajcn/40.5.1090|doi-access=free}}</ref> Given that estimates suggest 127 million preschool children worldwide are vitamin A deficient, this population has the potential for increased risk of disease contraction.<ref>{{cite journal|vauthors=West KP|title=Extent of vitamin A deficiency among preschool children and women of reproductive age|journal=The Journal of Nutrition|volume=132|issue=9 Suppl|pages=2857S–2866S|date=September 2002|pmid=12221262|doi=10.1093/jn/132.9.2857S|doi-access=free}}</ref>

===Malabsorption===
{{Main|Malabsorption}}
[[Malabsorption]] is the inability to absorb food fully, mostly from disorders in the small bowel, but also due to maldigestion from diseases of the [[pancreas]].

Causes include:{{citation needed|date=June 2021}}
* ''enzyme deficiencies or mucosal abnormality'', as in [[food allergy]] and [[food intolerance]], e.g. [[celiac disease]] (gluten intolerance), [[lactose intolerance]] (intolerance to milk sugar, common in non-Europeans), and [[fructose malabsorption]].
* ''[[pernicious anemia]]'', or impaired bowel function due to the inability to absorb [[vitamin B12|vitamin B<sub>12</sub>]],
* ''loss of pancreatic secretions'', which may be due to [[cystic fibrosis]] or [[pancreatitis]],
* ''structural defects'', like [[short bowel syndrome]] (surgically removed bowel) and radiation fibrosis, such as usually follows cancer treatment and other drugs, including agents used in [[chemotherapy]]; and
* ''certain drugs'', like [[orlistat]], which inhibits the absorption of fat.

===Inflammatory bowel disease===
{{Main|Inflammatory bowel disease}}
The two overlapping types here are of unknown origin:
* [[Ulcerative colitis]] is marked by chronic bloody diarrhea and inflammation mostly affects the distal [[colon (anatomy)|colon]] near the [[rectum]].
* [[Crohn's disease]] typically affects fairly well demarcated segments of bowel in the colon and often affects the end of the small bowel.

===Irritable bowel syndrome===
{{Main|Irritable bowel syndrome}}
Another possible cause of diarrhea is irritable bowel syndrome (IBS), which usually presents with abdominal discomfort relieved by [[defecation]] and unusual [[Human feces|stool]] (diarrhea or [[constipation]]) for at least three days a week over the previous three months.<ref>{{cite journal | vauthors = Longstreth GF, Thompson WG, Chey WD, Houghton LA, Mearin F, Spiller RC | title = Functional bowel disorders | journal = Gastroenterology | volume = 130 | issue = 5 | pages = 1480–91 | date = April 2006 | pmid = 16678561 | doi = 10.1053/j.gastro.2005.11.061 }}</ref> Symptoms of diarrhea-predominant IBS can be managed through a combination of dietary changes, soluble fiber supplements and medications such as [[loperamide]] or [[codeine]]. About 30% of patients with diarrhea-predominant IBS have [[bile acid malabsorption]] diagnosed with an abnormal [[SeHCAT]] test.<ref>{{cite journal | vauthors = Wedlake L, A'Hern R, Russell D, Thomas K, Walters JR, Andreyev HJ | title = Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome | journal = Alimentary Pharmacology & Therapeutics | volume = 30 | issue = 7 | pages = 707–17 | date = October 2009 | pmid = 19570102 | doi = 10.1111/j.1365-2036.2009.04081.x | s2cid = 11327665 | doi-access = free }}</ref>

===Other diseases===
Diarrhea can be caused by other diseases and conditions, namely:
* Chronic [[ethanol]] ingestion<ref name="Harrison">{{cite book | vauthors = Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL | title = Harrison's Principles of Internal Medicine | location = New York | publisher = McGraw-Hill | date = 2005 | isbn = 978-0-07-139140-5 | title-link = Harrison's Principles of Internal Medicine }}</ref>
* [[Hyperthyroidism]]<ref name="pmid26576135">{{cite journal | vauthors = Lee KJ | title = Pharmacologic Agents for Chronic Diarrhea | journal = Intestinal Research | volume = 13 | issue = 4 | pages = 306–12 | date = October 2015 | pmid = 26576135 | pmc = 4641856 | doi = 10.5217/ir.2015.13.4.306 }}</ref>
* Certain medications<ref name="pmid26576135"/>
* [[Bile acid malabsorption]]<ref name="pmid26576135"/>
* [[Ischemia|Ischemic]] bowel disease: This usually affects older people and can be due to blocked arteries.
* [[Microscopic colitis]], a type of [[inflammatory bowel disease]] where changes are seen only on histological examination of colonic biopsies.
* [[Bile salt malabsorption]] ([[primary bile acid diarrhea]]) where excessive [[bile acids]] in the [[Colon (anatomy)|colon]] produce a secretory diarrhea.
* Hormone-secreting tumors: some hormones, e.g. [[serotonin]], can cause diarrhea if secreted in excess (usually from a tumor).
* Chronic mild diarrhea in infants and toddlers may occur with no obvious cause and with no other ill effects; this condition is called [[toddler's diarrhea]].
* [[Environmental enteropathy]]
* [[Radiation enteropathy]] following treatment for pelvic and abdominal cancers.
* [[Mast cell activation syndrome]] (MCAS)<ref>{{Cite journal |last1=Afrin |first1=Lawrence B. |last2=Self |first2=Sally |last3=Menk |first3=Jeremiah |last4=Lazarchick |first4=John |date=2016-12-16 |title=Characterization of Mast Cell Activation Syndrome |journal=The American Journal of the Medical Sciences |language=en |volume=353 |issue=3 |pages=207–215 |doi=10.1016/j.amjms.2016.12.013 |pmid=28262205 |pmc=5341697 }}</ref><ref>{{Cite journal |last1=Molderings |first1=Gerhard J. |last2=Haenisch |first2=Britta |last3=Brettner |first3=Stefan |last4=Homann |first4=Jürgen |last5=Menzen |first5=Markus |last6=Dumoulin |first6=Franz Ludwig |last7=Panse |first7=Jens |last8=Butterfield |first8=Joseph |last9=Afrin |first9=Lawrence B. |date=2016 |title=Pharmacological treatment options for mast cell activation disease |journal=Naunyn-Schmiedeberg's Archives of Pharmacology |language=en |volume=389 |issue=7 |pages=671–694 |doi=10.1007/s00210-016-1247-1 |pmid=27132234 |pmc=4903110 }}</ref><ref>{{Cite journal |last1=Valent |first1=Peter |last2=Akin |first2=Cem |last3=Nedoszytko |first3=Boguslaw |last4=Bonadonna |first4=Patrizia |last5=Hartmann |first5=Karin |last6=Niedoszytko |first6=Marek |last7=Brockow |first7=Knut |last8=Siebenhaar |first8=Frank |last9=Triggiani |first9=Massimo |last10=Arock |first10=Michel |last11=Romantowski |first11=Jan |last12=Górska |first12=Aleksandra |last13=Schwartz |first13=Lawrence B. |last14=Metcalfe |first14=Dean D. |date=2020-11-27 |title=Diagnosis, Classification and Management of Mast Cell Activation Syndromes (MCAS) in the Era of Personalized Medicine |journal=International Journal of Molecular Sciences |language=en |volume=21 |issue=23 |page=9030 |doi=10.3390/ijms21239030 |doi-access=free |pmid=33261124 |pmc=7731385 }}</ref>

===Medications===
Over 700 medications, such as [[side effects of penicillin|penicillin]], are known to cause diarrhea.<ref>{{cite book | vauthors = Vallerand A | title = Davis's drug guide for nurses | publisher = F.A. Davis Company | location = Philadelphia | year = 2017 | isbn = 978-0-8036-5705-2 |pages=989–994}}</ref><ref>{{cite web | vauthors = Dekel R, Sperber AD |url=https://www.iffgd.org/lower-gi-disorders/diarrhea/diarrhea-incontinence-caused-by-medication.html |title=Diarrhea & Incontinence Caused by Medication | publisher = International Foundation for Gastrointestinal Disorders (IFFGD) |access-date=18 May 2017 |url-status=live |archive-url=https://web.archive.org/web/20170224195533/https://www.iffgd.org/lower-gi-disorders/diarrhea/diarrhea-incontinence-caused-by-medication.html |archive-date=24 February 2017 }}</ref> The classes of medications that are known to cause diarrhea are laxatives, antacids, heartburn medications, antibiotics, anti-neoplastic drugs, anti-inflammatories as well as many dietary supplements.<ref name="MoonZhang2015">{{cite journal | vauthors = Moon C, Zhang W, Sundaram N, Yarlagadda S, Reddy VS, Arora K, Helmrath MA, Naren AP | title = Drug-induced secretory diarrhea: A role for CFTR | journal = Pharmacological Research | volume = 102 | pages = 107–112 | date = December 2015 | pmid = 26429773 | pmc = 4684461 | doi = 10.1016/j.phrs.2015.08.024 }}</ref>