What are the causes of chronic diarrhea in children?

Causes of Chronic Diarrhea in Children

Chronic diarrhea in children has an age-dependent spectrum of causes, with infectious and post-infectious enteropathies, food allergies (particularly cow's milk protein), and celiac disease being the most common across all age groups, while congenital diarrheas dominate in neonates and inflammatory bowel disease increases dramatically in older children and adolescents. 1, 2, 3

Age-Specific Etiologic Framework

Neonates and Young Infants (0-2 years)

Congenital diarrheas and enteropathies (CODEs) are rare but devastating causes in this age group and include: 4, 5

• Disorders of intestinal ion transport presenting at birth with polyhydramnios, showing normal villus architecture on biopsy 4
• Microvillus inclusion disease, tufting enteropathy, autoimmune enteropathy, and IPEX syndrome characterized by villus blunting 4
• Persistent intestinal infections and post-infectious enteropathy remain major contributors 2
• Cow's milk protein allergy accounts for approximately 17% of cases in this age group 3

Toddlers and Young Children (2-5 years)

• Celiac disease emerges as the leading cause, accounting for approximately 30% of cases 3
• Cow's milk protein allergy remains significant at 17% 3
• Toddler's diarrhea (chronic nonspecific diarrhea) becomes more common 2
• Bacterial and parasitic infections including Giardia and Cryptosporidium account for 26% of cases 3
• Post-infectious gastroenteritis with persistent enteropathy represents 10% 3

Older Children and Adolescents (>5 years)

• Inflammatory bowel disease (Crohn's disease and ulcerative colitis) shows strongly increasing prevalence 6, 2
• Celiac disease remains a major cause throughout childhood 2, 3
• Microscopic colitis should be considered 6
• Nonspecific diarrhea is frequent in this age group 2

Pathophysiologic Categories Across All Ages

Malabsorptive Causes (Steatorrhea - pale, bulky, foul-smelling stools)

• Celiac disease is the most common small bowel enteropathy in Western populations 6
• Cystic fibrosis accounts for approximately 10% of cases 3
• Chronic pancreatitis and pancreatic insufficiency 6
• Bile acid malabsorption, particularly after ileal resection or in diabetic children 6

Inflammatory Causes (Bloody or mucoid stools)

• Ulcerative colitis and Crohn's disease cause inflammatory diarrhea 6
• Eosinophilic gastroenteritis is rare but important 3
• Autoimmune enteropathy in neonates and young infants 4

Secretory/Osmotic Causes (Watery stools)

• Food intolerances including lactose intolerance and FODMAP sensitivity 6
• Congenital disorders of ion transport in neonates 4
• Endocrine disorders including hyperthyroidism and diabetes mellitus 6

Critical Diagnostic Approach by Stool Characteristics

Watery Diarrhea

Evaluate for: 5

• Congenital disorders of electrolyte transport (neonates with normal villus architecture)
• Secretory tumors (rare in children)
• Endocrine causes (thyroid function testing mandatory) 6
• Toddler's diarrhea (diagnosis of exclusion)

Fatty Stools (Steatorrhea)

Investigate for: 5

• Celiac disease (IgA tissue transglutaminase with total IgA) 6
• Cystic fibrosis (sweat chloride test) 3
• Pancreatic insufficiency
• Bile acid malabsorption (particularly post-surgical or diabetic patients) 6

Bloody Diarrhea

Requires urgent evaluation for: 5

• Inflammatory bowel disease (fecal calprotectin >90% sensitive) 6
• Infectious colitis (bacterial and parasitic pathogens)
• Allergic colitis in infants

Essential First-Line Investigations

Basic screening must include: 6, 3

• Complete blood count (anemia has high specificity for organic disease, iron deficiency highly sensitive for celiac disease)
• Erythrocyte sedimentation rate and C-reactive protein (abnormalities have high specificity for organic pathology)
• IgA tissue transglutaminase with total IgA (celiac screening)
• Thyroid-stimulating hormone (best predictor for hyperthyroidism)
• Stool studies including culture, ova and parasites, and fecal calprotectin
• Sweat chloride test (cystic fibrosis screening) 3
• Cow's milk protein skin prick test in younger children 3

Critical Red Flags Requiring Urgent Investigation

The following features mandate immediate advanced evaluation: 6, 1

• Malnutrition or failure to thrive (present in 80% of chronic diarrhea cases) 3
• Diarrhea beginning in the neonatal period (suggests congenital enteropathy)
• Nocturnal diarrhea (essentially rules out functional disorders)
• Blood in stools (requires colonoscopy)
• Weight loss (excludes functional disorders)
• Family history of inflammatory bowel disease, celiac disease, or immunodeficiency 6

Iatrogenic and Dietary Causes

Medications cause up to 4% of chronic diarrhea cases in children: 6

• Magnesium-containing products
• Antibiotics (also consider Clostridium difficile)
• Antineoplastic agents
• Theophyllines

Dietary factors include: 6

• Excessive sorbitol and fructose intake
• FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols)
• Excessive caffeine or juice consumption

Advanced Diagnostic Pathway

When initial screening is unrevealing, proceed with: 1, 5

• Upper endoscopy with small bowel biopsies to assess villus-to-crypt ratio and identify enteropathies
• Colonoscopy with biopsies for suspected inflammatory bowel disease or microscopic colitis
• Genetic testing (whole-exome or genome sequencing) for congenital diarrheas, monogenic IBD, and immunodeficiency disorders 1, 5
• Breath tests for carbohydrate malabsorption
• Imaging studies as clinically indicated

Common Pitfalls to Avoid

• Do not dismiss nocturnal symptoms as functional - this pattern demands thorough organic disease evaluation 6
• Do not overlook nutritional consequences - 80% of children with chronic diarrhea develop malnutrition 3
• Do not delay genetic evaluation in neonates with severe diarrhea and normal infection workup 1, 5
• Do not forget medication review - systematically assess all medications and supplements 6
• Do not assume viral gastroenteritis - post-infectious enteropathy can persist for months 2, 3