Chronic Diarrhea

Chronic Diarrhea is a topic covered in the 5-Minute Pediatric Consult.

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Basics

Description

  • Chronic diarrhea is defined as stool output >200 g/24 h in children and adults, or 10 g/kg/24 h in infants, that has occurred for >30 days.
  • Should be differentiated from acute diarrhea, which is generally caused by enteric pathogens, is self-limiting, and has a duration of symptoms <14 days; as well as persistent diarrhea, which lasts 14 to 29 days

Epidemiology

  • Gender and genetic factors do not play a significant role in most cases of chronic diarrhea.
  • Infectious chronic diarrhea is seen most commonly in low-resource settings.

Pathophysiology

The two major categories of chronic diarrhea are osmotic and secretory. Inflammatory and motility disorders are important subcategories to consider.

  • Osmotic diarrhea occurs when unabsorbable solute accumulates in the lumen of the small intestine and colon, increasing intraluminal osmotic pressure and resulting in excessive fluid and electrolyte losses in stool.
    • Osmotic diarrhea will improve with fasting.
    • Osmotic diarrhea is usually related to malabsorption of dietary products or to the presence of congenital or acquired disaccharidase deficiency or glucose–galactose defects.
  • Secretory diarrhea occurs when the net secretion of fluid and electrolyte is in excess of absorption in the intestine:
    • Secretory diarrhea occurs independently of the osmotic load in the intestinal lumen
    • Will not improve with fasting
    • The mechanisms for secretory diarrhea include the activation of intracellular mediators such as cAMP, cGMP, and calcium-dependent channels.
    • These mediators stimulate active chloride secretion from the crypt cells and inhibit the neutral coupled sodium chloride absorption.
  • Inflammation in the intestine can cause an alteration in mucosal integrity resulting in exudative loss of mucus, blood, and/or protein. Increased permeability and altered mucosal surface area may affect absorption and result in diarrhea due to malabsorption.
  • Motility disorders affect intestinal transit time. Hypomotility can allow stasis from bacterial overgrowth and can lead to diarrhea.

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