Diarrhea is usually categorized into either malabsorptive type (i.e. osmotic) or secretory type (e.g. inflammatory or infectious). Malabsorptive diarrhea implies poor digestion and/or absorptive capacity.  Secretory diarrhea implies compromise of the mucosal barrier and active loss of intestinal fluid.

Diarrhea is a concerning complaint as it can result in dehydration and poor weight gain. An important measure of hydration is urine output, which should be carefully noted by the parents. Stool tests are important in the evaluation of diarrhea and will help determine the nature of the condition.