What investigations should be performed for a 1-year-old presenting with acholic stools?

Diagnostic Approach for a 1-Year-Old with White (Acholic) Stools

Acholic stools in a 1-year-old child warrant urgent investigation for biliary obstruction, with liver function tests and abdominal ultrasound as the first-line investigations.

Initial Assessment

When evaluating a 1-year-old with white or acholic stools, the following investigations should be performed immediately:

First-line Investigations:

• Complete blood count (FBC)
• Liver function tests (LFTs) including:
  • Bilirubin (total and direct/conjugated)
  • Alkaline phosphatase (ALP)
  • Gamma-glutamyl transferase (GGT)
  • Aspartate aminotransferase (AST)
  • Alanine aminotransferase (ALT)
• Abdominal ultrasound to evaluate:
  • Liver parenchyma and size
  • Biliary tract anatomy
  • Gallbladder presence and size
  • Presence of choledochal cyst
  • Spleen size

Second-line Investigations:

• Stool analysis for color confirmation and microscopy/culture
• Clostridium difficile testing as recommended for gastrointestinal evaluation 1

Imaging Studies

The choice of imaging studies should be guided by the initial ultrasound findings:

1. If ultrasound suggests biliary obstruction:

   • MRCP (Magnetic Resonance Cholangiopancreatography) to visualize the biliary tree non-invasively

2. If biliary atresia is suspected:

   • Hepatobiliary scintigraphy to assess bile flow
   • Liver biopsy may be necessary for definitive diagnosis

3. If malrotation is suspected:

   • Upper GI series is the gold standard with 96% sensitivity 2

Diagnostic Considerations

Key Differential Diagnoses:

1. Biliary atresia - typically presents earlier but can have late manifestations 3
2. Choledochal cyst - can present with acholic stools and jaundice in infants 4
3. Biliary obstruction from other causes:
   • Gallstones
   • Tumor
   • Stricture
4. Metabolic liver diseases
5. Infectious hepatitis

Important Clinical Correlations:

• Acholic stools have been reported as a sensitive marker (77%) for biliary atresia, though specificity is poor (51%) 5
• The presence of a firm/hard liver and hepatomegaly ≥4 cm should raise suspicion for biliary atresia 5
• Some children with biliary atresia may initially have pigmented stools that later become acholic, necessitating repeated stool color assessment 5

Practical Considerations

• Mobile applications for stool color recognition have shown high sensitivity (100%) and specificity (99%) for identifying acholic stools and may be helpful in monitoring 6
• Early detection of biliary obstruction is critical for improved outcomes, particularly in conditions like biliary atresia where timely surgical intervention can be lifesaving 3
• Stool color cards have proven useful for early detection of neonatal cholestasis from various causes 7

Follow-up Recommendations

Based on initial test results:

• If biliary obstruction is confirmed: urgent referral to pediatric gastroenterology and pediatric surgery
• If initial tests are inconclusive but acholic stools persist: close monitoring with repeat liver function tests and imaging within 1-2 weeks
• Consider liver biopsy if diagnosis remains unclear after non-invasive investigations

Early identification and management of the underlying cause of acholic stools is essential to prevent progressive liver damage and improve long-term outcomes.