Usually both categories are present in chronic diarrhea of infants.Secretory diarrhea can be caused by either infectious or non-infectious agents. Infectious agents include bacteria, viruses, and protozoans while non-infectious agents can be hormones, neurotransmitters, cytokines, and others. Osmotic diarrhea occurs when nutrients that are not absorbed exists in the intestines, typically due to damage to the intestines. The nutrients that are unable to be absorbed in the intestines draws water to itself.Some factors that lead to chronic diarrhea of infancy:
Underdeveloped digestive system, nutrients do not spend adequate time in the digestive tract for water to be absorbed which leads to diarrhea. Imbalanced Diet - a diet that has excess fiber and/or a lack of fat, fat can slow down the digestion process and prolong the amount of time nutrients spend in the tract which increases absorption. Fiber can lead to diarrhea because it shortens the amount of time food spends in the intestines, decreasing absorption. Inability to absorb carbohydratesThe specific source of chronic diarrhea typically depends on the age of the infant/child. Diarrhea is uncommon for newborns; consequently, its presence in newborns could indicate a congenital disorder which would need hospitalization. Rare causes of chronic diarrhea in young children include a group of genetic mutations known as "congenital diarrhea and enteropathies" (CODEs). This group of genetic disorders usually presents in the first weeks of birth as severe and debilitating diarrhea and can lead to malabsorption, growth failure, and difficulty feeding.
travel)Evaluation of past medical history includes:
Family history
Conditions such as inflammatory bowel disease, cystic fibrosis, and celiac diseasePhysical examination involves:
Abdominal examination (tenderness, distention, and/or bowel sounds)
Genital examination (rashes, anal fissures, and/or ulcerative lesions)
General assessment and vital signs (any signs of dehydration such as tachycardia and low blood pressure)
Examination of extremities and head (any signs of dehydration such as dry mucous membranes and skin turgor)

Diagnostic Tests
The following tests can also be performed to assist in the diagnosis of toddlers diarrhea and evaluation of any associated complications/underlying conditions:
Stool tests provide further information about bleeding, infectious agents, and/or anatomical problems. Blood tests allow assessment of inflammatory markers and/or other criterion for causative diseases. X-rays provide evaluations of any problems that may originate in the gastrointestinal tract/liver/etc. Upper endoscopy or colonoscopy allows visualization of the gastrointestinal tract to assess location of inflammation. Breath hydrogen tests are utilized to determine lactose, fructose, and/or sucrose intolerance. Small intestinal bacterial overgrowth (SIBO) may also be indicated by this test. Genetic Testing
Most commonly, chronic diarrhea in infants and children are classified as acquired diarrhea, identified with the general diagnostic tests mentioned above. The other classification of chronic diarrhea, congenital diarrheas and enteropathies (CODEs), are rare diagnoses of exclusion. With recent advances in genome sequencing, the addition of targeted genetic testing to diagnostic algorithms has been proposed to allow faster diagnoses and earlier treatment of CODEs. While certain genes and mutations have been associated with various CODEs, further research and studies are necessary to support the role of diagnostic genetic testing.