Diarrhea refers to the expulsion of a high volume of liquid stool. It can be accompanied by blood or mucous, depending on the reason for the diarrhea. Risks associated with diarrhea include dehydration and electrolyte imbalances.
Infections
Most causes of diarrhea in children are due to viral or bacterial infections. A common virus is the rotavirus, which is the leading cause of gastroenteritis and dehydration in the United States, as well as a leading cause of hospitalization for children. Other viruses include the Norwalk virus, which has caused well-publicized outbreaks of diarrhea in cruise ships around the world, and the cholera virus, which continues to cause significant diarrheal illnesses in developing countries.
Bacterial causes of diarrhea include E.coli, Salmonella and Shigella. Most outbreaks of these bacteria tend to follow the consumption of poorly handled or uncooked foodstuffs. The diarrhea caused by these bacteria is often accompanied by blood and can lead to bacteremia, or blood-borne infection, that can cause problems in the kidneys and other complications.
Malabsorption
Malabsorption occurs when children lack enzymes in their gut to properly absorb nutrients. When these nutrients remain in the lumen of the intestines, they pull water from the tissues, causing diarrhea. Common conditions in children that can present this way include lactose intolerance and celiac disease, a condition in which children can't absorb gluten-containing products like wheat, rye and barley. Other conditions than can cause malabsorption and diarrhea in children include cystic fibrosis and pancreatic insufficiency. In both of these conditions the pancreas is unable to secrete enzymes that are essential for digestion, leaving undigested food in the digestive system, which can then lead to diarrhea. Other foods than can cause diarrhea include too much caffeine or fructose-containing products, like certain fruit juices.
Systemic Illnesses
Inflammatory bowel disease, like Crohn's disease and ulcerative colitis, can lead to inflammation in the colon, which can decrease its ability to absorb nutrients. A common presentation of inflammatory bowel disease in children is bloody diarrhea. Hyperthyroidism, or an overactive thyroid, can also present with diarrhea, as well as other symptoms like tachycardia, restlessness and increased sweating. Another cause of diarrhea in children is giving them laxatives for constipation, which can then lead to frequent liquid stools.
