Toddler diarrhea, also known as chronic nonspecific diarrhea (CNSD), is a benign cause of chronic diarrhea characterized by the passage of nonbloody, nonpainful, loose bowel movements daily without growth failure.

Diarrhea is defined as increased frequency, volume, or wateriness of the stool. This is generally accepted as more than 3 stools a day, or a total daily weight of more than 200-250 g. A volume over 20 g/kg/day is used for children who weigh less than 10 kg. Stooling frequency and volumes can be quite different between toddlers, so comparing new bowel habits to baseline patterns can be helpful when evaluating for diarrhea. Chronic diarrhea occurs when diarrhea has been present for at least 4 weeks.

In toddler diarrhea, stools may appear brown, yellow, or green, and may contain undigested food particles. These bowel movements are neither bloody nor painful, and can occur more than 3 times a day with no subsequent growth failure. The episodes of diarrhea occur mainly during the day, although up to 25% of children with toddler diarrhea may pass stools at nighttime as well.

It is usually seen in well-appearing children ages 6 months to 5 years, most commonly among children 2-4 years old. This is the most common form of chronic diarrhea in a child who is gaining weight and growing normally. Importantly, toddler diarrhea does not have associated abdominal pain, fever, vomiting, weight loss, or issues with weight gain.

Pathophysiology: There are 4 mechanisms of diarrhea: increased intestinal secretion, decreased intestinal absorption, abnormal motility, and increased osmotic load. While CNSD is an osmotic diarrhea, infectious, inflammatory, and secretory etiologies should be considered since toddler diarrhea is a diagnosis of exclusion.

The rapid transit of food and fluid through a child's intestinal tract results in the subsequent lack of time to absorb water, bile, or sugars back into the bloodstream from the intestinal surface. When excess bile is in the stool, a yellow or green appearance may arise. When there is excess undigested sugar or water in the intestines, the stools will be loose and more frequent. The presence of undigested high fiber materials (such as fruits and vegetables) may appear "whole" or as undigested particles in the stool. As a result, the bacterial flora in the large intestines will gain access to the excess undigested sugars, creating more sugars and fluid as a byproduct, producing loose and/or "explosive" stools because of the gassiness.

Food contributors: Toddler diarrhea is exacerbated by the ingestion of osmotically active carbohydrates (eg, fruit juices). Stools are typically more formed in the morning and worsen in the afternoon and evening, coinciding with the ingestion of osmotically active foods. High-fiber foods (fruits and vegetables) may act as a contributor.

Emergent considerations: Infectious, inflammatory, and secretory etiologies should be considered as toddler diarrhea is a diagnosis of exclusion. Fever, chills, night sweats, associated abdominal pain, vomiting, weight loss, or failure to gain weight indicate a more serious pathology. Abnormal vital signs should also signify that the patient has a more serious and emergent etiology at play.