What is the best treatment approach for a child with chronic diarrhea, considering their age, past medical history, and potential allergies?

Workup for Chronic Diarrhea in a Child

The workup for chronic diarrhea in children should begin with a detailed history focusing on age of onset, stool characteristics (watery, bloody, fatty, mucoid), dietary patterns, growth parameters, and alarm features, followed by targeted laboratory and imaging studies based on the clinical presentation. 1

Initial Clinical Assessment

History and Physical Examination

Obtain the following specific details:

• Age of onset - etiology varies significantly by age, with toddler's diarrhea common in ages 1-3 years, while inflammatory bowel disease typically presents after age 5 1, 2
• Stool characteristics - watery suggests osmotic or secretory causes; bloody indicates inflammatory disease; fatty/greasy suggests malabsorption 1
• Growth parameters - weight loss or growth failure indicates organic disease requiring aggressive workup 1
• Dietary history - excessive juice intake, recent dietary changes, food intolerances 1
• Family history - celiac disease, inflammatory bowel disease, cystic fibrosis 2

Alarm Features Requiring Immediate Investigation

The presence of any of these features mandates comprehensive workup: 1, 2

• Weight loss or failure to thrive
• Bloody diarrhea
• Nocturnal diarrhea
• Fever
• Severe abdominal pain
• Perianal disease
• Arthritis or skin manifestations

Laboratory Workup

First-Tier Tests (Perform in All Cases)

• Complete blood count - anemia suggests inflammatory bowel disease or celiac disease; eosinophilia suggests allergic or parasitic causes 2
• Comprehensive metabolic panel - electrolyte abnormalities, renal function, albumin (low in protein-losing enteropathy) 2
• Inflammatory markers - ESR and CRP elevated in inflammatory bowel disease 2
• Stool studies - culture for bacterial pathogens, ova and parasites (×3 samples), Giardia and Cryptosporidium antigen, Clostridium difficile toxin 1, 2
• Stool pH and reducing substances - pH <5.5 and positive reducing substances indicate carbohydrate malabsorption 1
• Fecal calprotectin - elevated in inflammatory bowel disease 2

Second-Tier Tests (Based on Initial Results)

If malabsorption suspected (fatty stools, poor growth): 1, 2

• Tissue transglutaminase IgA with total IgA for celiac disease
• Sweat chloride test for cystic fibrosis
• 72-hour fecal fat collection (gold standard for fat malabsorption)
• Pancreatic elastase in stool

If inflammatory disease suspected (bloody stools, elevated inflammatory markers): 2

• Upper and lower endoscopy with biopsies
• Small bowel imaging (MR enterography or CT enterography)

If immune deficiency suspected (recurrent infections, failure to thrive): 2

• Immunoglobulin levels (IgA, IgG, IgM, IgE)
• HIV testing
• Lymphocyte subsets

If endocrine causes suspected (polyuria, polydipsia, growth abnormalities): 2

• Thyroid function tests
• Morning cortisol
• Consider VIP and gastrin levels if secretory diarrhea with large volumes

Age-Specific Considerations

Infants (<1 year)

Focus on: 1

• Cow's milk protein allergy (trial of extensively hydrolyzed or amino acid formula)
• Congenital disorders (microvillus inclusion disease, congenital chloride diarrhea)
• Post-infectious enteropathy
• Primary immunodeficiencies

Toddlers (1-3 years)

Most common cause is toddler's diarrhea (functional) - diagnosis of exclusion with normal growth, no alarm features, and excessive fluid/juice intake 1

Also consider: 1

• Giardiasis
• Celiac disease
• Food allergies

School-age and Adolescents

Higher likelihood of: 2

• Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
• Celiac disease
• Irritable bowel syndrome
• Lactose intolerance

Common Pitfalls to Avoid

• Do not assume functional diarrhea without documenting normal growth - weight loss or growth failure always indicates organic disease 1
• Do not overlook factitious diarrhea - consider in cases with inconsistent history or when parents have medical backgrounds 2
• Do not forget to check total IgA before relying on tissue transglutaminase IgA - IgA deficiency causes false negatives 2
• Do not delay endoscopy when alarm features present - bloody diarrhea, weight loss, or elevated inflammatory markers require direct visualization 2

Nutritional Assessment During Workup

While conducting the workup, ensure adequate nutrition: 1

• Monitor weight and height at each visit
• Provide age-appropriate diet without unnecessary restrictions
• Consider nutritional supplementation if growth faltering present
• Breaking the vicious cycle of malnutrition and diarrhea is essential for recovery 1