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 enzymes in order to break them down into their nutrient components, which are then absorbed into the bloodstream via the 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.<unk>  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. Acute<unk>  is most commonly due to viral gastroenteritis with rotavirus, which accounts for 40% of cases in children under five. In travelers, however, bacterial infections predominate. Various toxins such as mushroom poisoning and drugs can also cause acute<unk> . Chronic<unk>  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. Infections There are many causes of infectious<unk> , which include viruses, bacteria and parasites. Infectious<unk>  is frequently referred to as gastroenteritis. Norovirus is the most common cause of viral<unk>  in adults, but rotavirus is the most common cause in children under five years old. Adenovirus types 40 and 41, and astroviruses cause a significant number of infections. Shiga-toxin producing Escherichia coli, such as E coli o157:h7, are the most common cause of infectious bloody<unk>  in the United States. Campylobacter spp. are a common cause of bacterial<unk> , but infections by Salmonella spp., Shigella spp. and some strains of Escherichia coli are also a frequent cause. In the elderly, particularly those who have been treated with antibiotics for unrelated infections, a toxin produced by Clostridioides difficile often causes severe<unk> . Parasites, particularly protozoa e.g., Cryptosporidium spp., Giardia spp., Entamoeba histolytica, Blastocystis spp., Cyclospora cayetanensis, are frequently the cause of<unk>  that involves chronic infection. The broad-spectrum antiparasitic agent nitazoxanide has shown efficacy against many<unk> -causing parasites. Other infectious agents, such as parasites or bacterial toxins, may exacerbate symptoms. 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,<unk>  can lead to severe dehydration and can become life-threatening. Sanitation Poverty often leads to unhygienic living conditions, as in this community in the Indian Himalayas. Such conditions promote contraction of<unk> l diseases, as a result of poor sanitation and hygiene. Open defecation is a leading cause of infectious<unk>  leading to death. Poverty is a good indicator of the rate of infectious<unk>  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<unk> . "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<unk> ... Poverty also restricts the ability to provide age-appropriate, nutritionally balanced diets or to modify diets when<unk>  develops so as to mitigate and repair nutrient losses. The impact is exacerbated by the lack of adequate, available, and affordable medical care." One of the most common causes of infectious<unk>  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. Nutrition Proper nutrition is important for health and functioning, including the prevention of infectious<unk> . 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. Indeed, this relationship between zinc deficiency and reduced immune functioning corresponds with an increased severity of infectious<unk> . Children who have lowered levels of zinc have a greater number of instances of<unk> , severe<unk> , and<unk>  associated with fever. Similarly, vitamin A deficiency can cause an increase in the severity of<unk> l 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 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 The two overlapping types here are of unknown origin: * Ulcerative colitis is marked by chronic bloody<unk>  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 Another possible cause of<unk>  is irritable bowel syndrome (IBS), which usually presents with abdominal discomfort relieved by defecation and unusual stool<unk>  or constipation) for at least three days a week over the previous three months. Symptoms of<unk> -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<unk> -predominant IBS have bile acid malabsorption diagnosed with an abnormal SeHCAT test. Other diseases<unk>  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<unk>  where excessive bile acids in the colon produce a secretory<unk> . * Hormone-secreting tumors: some hormones, e.g. serotonin, can cause<unk>  if secreted in excess (usually from a tumor). * Chronic mild<unk>  in infants and toddlers may occur with no obvious cause and with no other ill effects; this condition is called toddler's<unk> . * Environmental enteropathy * Radiation enteropathy following treatment for pelvic and abdominal cancers. Medications Some medications, such as the penicillum can cause<unk> . Over 700 medications are known to cause<unk> . The classes of medications that are known to cause<unk>  are laxatives, antacids, heartburn medications, antibiotics, anti-neoplastic drugs, anti-inflammatories as well as many dietary supplements.
Diarrhea
Vomiting
Nausea
Constipation
Catarrh
Pseudodiarrhea
Adipsia
Thirst