Editing Diarrhea (section)

== Diagnostic approach ==

The following types of diarrhea may indicate further investigation is needed:

* In infants
* Moderate or severe diarrhea in young children
* Associated with blood
* Continues for more than two days
* Associated non-cramping [[abdominal pain]], [[fever]], [[weight loss]], etc.
* In [[Traveler's diarrhea|travelers]]
* In food handlers, because of the potential to infect others;
* In institutions such as hospitals, child care centers, or geriatric and convalescent homes.

A severity score is used to aid diagnosis in children.<ref name="pmid2371542">{{cite journal | vauthors = Ruuska T, Vesikari T | title = Rotavirus disease in Finnish children: use of numerical scores for clinical severity of diarrhoeal episodes | journal = Scandinavian Journal of Infectious Diseases | volume = 22 | issue = 3 | pages = 259–67 | year = 1990 | pmid = 2371542 | doi = 10.3109/00365549009027046 }}</ref>

When diarrhea lasts for more than four weeks a number of further tests may be recommended including:<ref>{{cite journal | vauthors = Arasaradnam RP, Brown S, Forbes A, Fox MR, Hungin P, Kelman L, Major G, O'Connor M, Sanders DS, Sinha R, Smith SC, Thomas P, Walters JR | title = Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition | journal = Gut | volume = 67 | issue = 8 | pages = 1380–1399 | date = August 2018 | pmid = 29653941 | pmc = 6204957 | doi = 10.1136/gutjnl-2017-315909 }}</ref>

* [[Complete blood count]] and a [[ferritin]] if [[anemia]] is present
* [[Thyroid stimulating hormone]]
* [[Tissue transglutaminase]] for [[celiac disease]]
* Fecal [[calprotectin]] to exclude [[inflammatory bowel disease]]
* [[Stool test]]s for ova and parasites as well as for ''[[Clostridioides difficile (bacteria)|Clostridioides difficile]]''
* A [[colonoscopy]] or fecal immunochemical testing for cancer, including biopsies to detect [[microscopic colitis]]
* Testing for [[bile acid diarrhea]] with [[SeHCAT]], [[7α-hydroxy-4-cholesten-3-one]] or fecal [[bile acids]] depending on availability
* [[Hydrogen breath test]] looking for [[lactose intolerance]]
* Further tests if [[immunodeficiency]], [[pelvic radiation disease]] or [[small intestinal bacterial overgrowth]] suspected.

A 2019 guideline recommended that testing for ova and parasites was only needed in people who are at high risk though they recommend routine testing for [[giardia]].<ref name=Sma2019>{{cite journal | vauthors = Smalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y | title = AGA Clinical Practice Guidelines on the Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D) | journal = Gastroenterology | volume = 157 | issue = 3 | pages = 851–854 | date = September 2019 | pmid = 31302098 | doi = 10.1053/j.gastro.2019.07.004 | doi-access = free }}</ref> [[Erythrocyte sedimentation rate]] (ESR) and [[C-reactive protein]] (CRP) were not recommended.<ref name=Sma2019/>