What lab tests are indicated for a 2-year-old girl presenting with steatorrhea (excess fat in stool)?

Diagnostic Approach for Steatorrhea in a 2-Year-Old Girl

For a 2-year-old girl presenting with steatorrhea, the initial laboratory workup should include fecal elastase, complete blood count, electrolytes, liver function tests, iron studies, vitamin B12, folate, thyroid function tests, and celiac disease screening.

Initial Laboratory Tests

• Fecal elastase should be performed as the first-line test to evaluate for exocrine pancreatic insufficiency 1
• Complete blood count to assess for anemia or signs of inflammation 1
• Serum electrolytes to evaluate for electrolyte imbalances 1
• Liver function tests to assess for hepatobiliary disease 1
• Iron studies, vitamin B12, and folate to evaluate for nutritional deficiencies 1
• Thyroid function tests to rule out thyroid disorders 1
• Serum anti-tissue transglutaminase IgA and total IgA to screen for celiac disease 2

Specific Tests for Pancreatic Function

• Fecal elastase is preferred over other pancreatic function tests due to its ease of use, requiring only a single stool sample 1
• Fecal elastase has good sensitivity for detecting moderate to severe pancreatic insufficiency but may miss mild disease 3
• If fecal elastase is abnormal, consider repeating the test as levels can fluctuate in the first year of life 1

Additional Testing Based on Initial Results

• If pancreatic insufficiency is suspected despite normal fecal elastase, consider:

  • Endoscopic direct pancreatic function testing (ePFT) for more sensitive assessment of pancreatic function 3
  • Upper gastrointestinal endoscopy with distal duodenal biopsies if small bowel malabsorption is suspected 1

• If cystic fibrosis is suspected (a common cause of steatorrhea in children):

  • Sweat chloride test should be performed 1, 4
  • Respiratory cultures may be considered if clinically indicated 1

Differential Diagnosis Considerations

• For small bowel causes of steatorrhea:

  • Celiac disease screening with anti-tissue transglutaminase antibodies 1
  • Consider food protein-induced enteropathy syndrome, which can present with steatorrhea in young infants 1

• For pancreatic causes:

  • Consider cystic fibrosis, which is an important cause of pancreatic insufficiency in children 1, 4
  • Evaluate for anatomical abnormalities of the pancreas if initial testing is inconclusive 4

Important Caveats

• The traditional three-day fecal fat collection is no longer recommended as the first-line test due to collection difficulties, lack of standardization, and limited diagnostic information 1
• Stool microscopy with Sudan stain can be used as a simple screening test but has limited sensitivity 5
• Avoid excessive testing in children to prevent overmedicalization and increased healthcare costs 1
• Pancreatic insufficiency in a child this young strongly suggests cystic fibrosis, which should be ruled out promptly 1, 4

By following this systematic approach, the underlying cause of steatorrhea in this young patient can be identified efficiently, allowing for appropriate management to improve nutritional status and quality of life.