How should I manage hard stools in a 6‑month‑old infant?

Management of Hard Stools in a 6-Month-Old Infant

For a 6-month-old with hard stools, start with fruit juices containing sorbitol (prune, pear, or apple juice) at 10 mL/kg body weight, and if this fails after a reasonable trial, advance to lactulose as the next-line agent. 1

Initial Assessment

Before treating, evaluate the following key features:

• Feeding history: Determine whether the infant is breastfed, formula-fed, or mixed-fed, and document any recent formula changes or introduction of solid foods 1
• Growth parameters: Check for poor weight gain or failure to thrive, which may signal an underlying organic cause requiring further workup 1
• Red flag symptoms: Look specifically for:
  • Bilious vomiting (suggests intestinal obstruction) 1
  • True acholic (clay-colored) stools, which indicate biliary obstruction and require immediate hepatology referral 2
  • Delayed passage of meconium in the neonatal period (raises concern for Hirschsprung disease) 2
• Perianal inspection: Visually examine for anal fissures, skin tags, or perianal redness 1
• Digital rectal exam is NOT necessary for functional constipation and should be reserved only for cases with red flags 1

First-Line Dietary Management

Fruit juices are the recommended first-line treatment for infants under 1 year with constipation. 1

• Give 10 mL/kg body weight of sorbitol-containing juices (prune, pear, or apple juice) 1
• These juices work by creating an osmotic load in the gastrointestinal tract due to their poorly absorbed sorbitol and carbohydrate content 1
• Caution: Avoid excessive juice consumption, as it may cause diarrhea, flatulence, abdominal pain, and poor weight gain 1

Second-Line Pharmacologic Treatment

If fruit juices fail, lactulose is the next recommended agent. 1

• Dosing for infants: The FDA-approved initial dose is 2.5 to 10 mL daily in divided doses 3
• Goal: Produce 2 to 3 soft stools daily 3
• If diarrhea develops, reduce the dose immediately; if diarrhea persists, discontinue lactulose 3
• Lactulose has been shown to be effective and safe in infants younger than 6 months 4
• Note: Polyethylene glycol (PEG/Macrogol) is NOT approved for infants under 6 months of age 4

Consider Cow's Milk Protein Intolerance

Cow's milk protein allergy can mimic functional constipation and should be considered, especially in formula-fed infants. 1

• For breastfed infants: Consider a 2- to 4-week maternal elimination diet that restricts at least milk and egg 1
• For formula-fed infants: Trial an extensively hydrolyzed or amino acid-based formula for 2 to 4 weeks 1
• Evidence shows that 24% of formula-fed infants with gastrointestinal symptoms (including constipation) resolved after switching to a protein hydrolysate formula 1

Additional Dietary Considerations

• Do NOT dilute formula: This does not help constipation and may compromise nutrition 1
• Ensure adequate hydration: For formula-fed infants, use full-strength formula and ensure adequate fluid intake 1
• Introduce age-appropriate solid foods if the infant is developmentally ready (at 6 months, many infants are ready to begin complementary foods) 1
• Continue breastfeeding on demand if the infant is breastfed 1

Parent Education and Monitoring

• Educate parents about normal bowel patterns: Stool frequency varies widely in infants, and infrequent stools alone do not always indicate constipation 1
• Instruct parents to monitor for warning signs and return if symptoms worsen 1
• Warning signs requiring immediate evaluation include:
  • Bilious vomiting 1
  • True clay-colored (acholic) stools 2
  • Poor weight gain or failure to thrive 1
  • Abdominal distension or hepatosplenomegaly 2

Common Pitfalls to Avoid

• Do not assume this is always functional constipation: While functional constipation accounts for 90-95% of cases in children, organic causes (Hirschsprung disease, hypothyroidism, spinal abnormalities) must be ruled out when red flags are present 5, 6
• Do not use PEG in infants under 6 months: It is not approved for this age group 4
• Do not overlook cow's milk protein intolerance: This is frequently missed and should be routinely considered during the milk-transition period 1
• Do not restrict breastfeeding: None of the functional gastrointestinal disorders is a reason to stop breastfeeding 4