severe diarrhea, and diarrhea associated with fever. 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, others suggest an increase in the rate associated with deficiency. given that estimates suggest 127 million preschool children worldwide are vitamin a deficient, this population has the potential for increased risk of disease contraction. malabsorption main article: 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: 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, 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 article: 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 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 article: irritable bowel syndrome another possible cause of diarrhea is irritable bowel syndrome (ibs), which usually presents with abdominal discomfort relieved by defecation and unusual stool (diarrhea or constipation) for at least three days a week over the previous three months. 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. other diseases diarrhea can be caused by other diseases and conditions, namely: chronic ethanol ingestion hyperthyroidism certain medications bile acid malabsorption 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 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. medications some medications, such as the penicillin can cause diarrhea. over 700 medications are known to cause diarrhea. 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. pathophysiology ion transporters targeted by enteric infections function transporter absorptionnhe, sglt1, enac, dra secretioncacc, nkcc1, cftr absorption and secretion sodium potassium atpase evolution according to two researchers, nesse and williams, diarrhea may function as an evolved expulsion defense mechanism. as a result, if it is stopped, there might be a delay in recovery. they cite in support of this argument research published in 1973 that found that treating shigella with the anti-diarrhea drug (co-phenotrope, lomotil) caused people to stay feverish twice as long as those not so treated. the researchers indeed themselves observed that: "lomotil may be contraindicated in shigellosis. diarrhea may represent a defense mechanism". 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 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. chronic diarrhea when diarrhea lasts for more than four weeks a number of further tests may be recommended including: 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 tests for ova and parasites as well as for 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. erythrocyte sedimentation rate (esr) and c-reactive protein (crp) were not recommended. prevention sanitation further information: wash § health aspects numerous studies have shown that improvements in drinking water and sanitation (wash) lead to decreased risks of diarrhoea. such improvements might include for example use of water filters, provision of high-quality piped water and sewer connections. in institutions, communities, and households, interventions that promote hand washing with soap lead to significant reductions in the incidence of diarrhea. the same applies to preventing open defecation at a community-wide level and providing access to improved sanitation. this includes use of toilets and implementation of the entire sanitation chain connected to the toilets (collection, transport, disposal or reuse of human excreta). there is limited evidence that safe disposal of child or adult feces can prevent diarrheal disease. hand washing basic sanitation techniques can have a profound effect on the transmission of diarrheal disease. the implementation of hand washing using soap and water, for example, has been experimentally shown to reduce the incidence of disease by approximately 30–48%. hand washing in developing countries, however, is compromised by poverty as acknowledged by the cdc: "handwashing is integral to disease prevention in all parts of the world; however, access to soap and water is limited in a number of less developed countries. this lack of access is one of many challenges to proper hygiene in less developed countries." solutions to this barrier require the implementation of educational programs that encourage sanitary behaviours. water given that water contamination is a major means of transmitting diarrheal disease, efforts to provide clean water supply and improved sanitation have the potential to dramatically cut the rate of disease incidence. in fact, it has been proposed that we might expect an 88% reduction in child mortality resulting from diarrheal disease as a result of improved water sanitation and hygiene. similarly, a meta-analysis of numerous studies on improving water supply and sanitation shows a 22–27% reduction in disease incidence, and a 21–30% reduction in mortality rate associated with diarrheal disease. chlorine treatment of water, for example, has been shown to reduce both the risk of diarrheal disease, and of contamination of stored water with diarrheal pathogens. vaccination immunization against the pathogens that cause diarrheal disease is a viable prevention strategy, however it does require targeting certain pathogens for vaccination. in the case of rotavirus, which was responsible for around 6% of diarrheal episodes and 20% of diarrheal disease deaths in the children of developing countries, use of a rotavirus vaccine in trials in 1985 yielded a slight (2–3%) decrease in total diarrheal disease incidence, while reducing overall mortality by 6–10%. similarly, a cholera vaccine showed a strong reduction in morbidity and mortality, though the overall impact of vaccination was minimal as cholera is not one of the major causative pathogens of diarrheal disease. since this time, more effective vaccines have been developed that have the potential to save many thousands of lives in developing nations, while reducing the overall cost of treatment, and the costs to society. rotavirus vaccine decreases the rates of diarrhea in a population. new vaccines against rotavirus, shigella, enterotoxigenic escherichia coli (etec), and cholera are under development, as well as other causes of infectious diarrhea. nutrition dietary deficiencies in developing countries can be combated by promoting better eating practices. zinc supplementation proved successful showing a significant decrease in the incidence of diarrheal disease compared to a control group. the majority of the literature suggests that vitamin a supplementation is advantageous in reducing disease incidence. development of a supplementation strategy should take into consideration the fact that vitamin a supplementation was less effective in reducing diarrhea incidence when compared to vitamin a and zinc supplementation, and that the latter strategy was estimated to be significantly more cost effective. breastfeeding breastfeeding practices have been shown to have a dramatic effect on the incidence of diarrheal disease in poor populations. studies across a number of developing nations have shown that those who receive exclusive breastfeeding during their first 6 months of life are better protected against infection with diarrheal diseases. one study in brazil found that non-breastfed infants were 14 times more likely to die from diarrhea than exclusively breastfed infants. exclusive breastfeeding is currently recommended for the first six months of an infant's life by the who, with continued breastfeeding until at least two years of age. others probiotics decrease the risk of diarrhea in those taking antibiotics. insecticide spraying may reduce fly numbers and the risk of diarrhea in children in a setting where there is seasonal variations in fly numbers throughout the year. management in many cases of diarrhea, replacing lost fluid and salts is the only treatment needed. this is usually by mouth – oral rehydration therapy – or, in severe cases, intravenously. diet restrictions such as the brat diet are no longer recommended. research does not support the limiting of milk to children as doing so has no effect on duration of diarrhea. to the contrary, who recommends that children with diarrhea continue to eat as sufficient nutrients are usually still absorbed to support continued growth and weight gain, and that continuing to eat also speeds up recovery of normal intestinal functioning. cdc recommends that children and adults with cholera also continue to eat. there is no evidence that early refeeding in children can cause an increase in inappropriate use of intravenous fluid, episodes of vomiting, and risk of having persistent diarrhea. medications such as loperamide (imodium) and bismuth subsalicylate may be beneficial; however they may be contraindicated in certain situations. fluids