What is the best course of treatment for a 7-week-old infant with constipation?

Management of Constipation in a 7-Week-Old Infant

For a 7-week-old infant with constipation, continue breastfeeding on demand or immediately resume full-strength formula after ensuring adequate hydration, while avoiding all laxatives and antidiarrheal medications at this age.

Critical First Step: Rule Out Red Flags

Before treating as functional constipation, you must exclude serious organic causes:

• Hirschsprung's disease is the most critical diagnosis to consider, occurring in 1 in 5,000 births and presenting with severe constipation from birth 1
• Look for delayed passage of meconium (>48 hours after birth), failure to thrive, bilious vomiting, or abdominal distension 2
• Examine for anorectal malformations, spinal cord abnormalities, and hypothyroidism 2
• If constipation has been present since birth or any red flags exist, refer immediately for specialist evaluation 3, 1

Initial Assessment

• Weigh the infant to establish baseline and assess for failure to thrive 4
• Examine for signs of dehydration: skin turgor, mucous membranes, mental status, pulse, and capillary refill 4
• Perform abdominal examination to assess for impaction or masses 2

Primary Treatment Approach for Functional Constipation

Feeding Management (Most Important)

• Breastfed infants: Continue nursing on demand without interruption, as breast milk naturally reduces stool issues 4
• Formula-fed infants: Use full-strength, lactose-free or lactose-reduced formula immediately 4
• Do NOT dilute formula or delay full-strength feeding, as this worsens outcomes 4

Hydration Support

• Ensure adequate fluid intake appropriate for age 5
• Mild dehydration itself can promote constipation, so maintaining euhydration is essential 5
• If dehydration is present, administer 50 mL/kg oral rehydration solution over 2-4 hours for mild dehydration 4

What NOT to Do (Critical Safety Information)

• Absolutely avoid all antidiarrheal agents (including loperamide) in neonates and children under 2 years due to risks of respiratory depression, cardiac arrest, and death 4
• Do not use stimulant laxatives (bisacodyl, senna) in infants this young—these are only appropriate for older children 6
• Avoid magnesium-based laxatives at this age 6
• Do not diagnose lactose intolerance based solely on stool pH or reducing substances without clinical symptoms 4

When to Reassess or Refer

Return immediately or refer if the infant develops:

• Irritability or lethargy 4
• Decreased urine output 4
• Intractable vomiting 4
• Persistent constipation despite conservative management 2
• Any signs suggesting Hirschsprung's disease 3, 1

Special Consideration: Infant Dyschezia

At 7 weeks, consider infant dyschezia (normal developmental phenomenon where infants strain and cry for 10-20 minutes before passing soft stools) 3. This is self-limited and requires only parental reassurance, not treatment 3.

Long-Term Perspective

Functional constipation in infants typically requires months of supportive intervention 1. Education and demystification for parents is essential, with reassurance that this is not life-threatening but may require prolonged management 1. Only 50-70% of children demonstrate long-term improvement despite treatment 2, emphasizing the importance of realistic expectations and close follow-up.