My 7-month-old infant has not passed a stool for three days; what should I do?

Management of a 7-Month-Old Unable to Pass Stool for 3 Days

Immediate Assessment

For a 7-month-old infant who has not passed stool for 3 days, the first priority is to rule out serious organic causes through targeted history and physical examination, then initiate treatment for functional constipation if no red flags are present. 1

Critical Red Flags to Exclude

• Delayed passage of meconium beyond 48 hours after birth (suggests Hirschsprung's disease) 2
• Bilious vomiting (indicates intestinal obstruction distal to the ampulla of Vater) 3, 4
• Abdominal distention with failure to pass gas (suggests mechanical obstruction) 4
• Blood in stool 3
• Fever, lethargy, or signs of systemic illness 5
• Poor weight gain or failure to thrive 5
• Abdominal tenderness or palpable mass 5

Key History Elements

• Stool pattern since birth: Hirschsprung's disease presents with chronic constipation from the neonatal period 1
• Consistency and caliber of stools: Hard, pellet-like stools or ribbon-like stools suggest functional constipation versus obstruction 2
• Painful defecation with screaming or stool-holding behaviors (typical of functional constipation) 6
• Recent dietary changes: Weaning or formula changes are common triggers 2
• Associated symptoms: Vomiting (especially if bilious), abdominal pain, or decreased activity 4

Physical Examination Priorities

• Abdominal examination: Check for distention, tenderness, palpable stool in left lower quadrant, or masses 1
• Perianal inspection: Rule out anal stenosis, fissures, or anteriorly displaced anus 1
• Digital rectal examination (if indicated): Assess for impacted stool, anal tone, and rectal vault size—though this is less commonly performed in infants due to distress 5
• Neurologic assessment: Check lower extremity tone and reflexes to exclude spinal cord abnormalities 1

Treatment Approach for Functional Constipation

First-Line Management (No Red Flags Present)

Polyethylene glycol (PEG) is the preferred first-line treatment for infants over 6 months with functional constipation. 7

• Dosing: Start with 0.5–1 g/kg/day of PEG powder mixed in liquid 7
• Duration: Continue for several months; relapse is common if stopped too early 1
• Alternative for infants under 6 months: Lactulose or lactitol-based medications are authorized and effective 7

If Fecal Impaction is Present

Disimpaction must be completed before starting maintenance therapy. 1, 7

• Oral route (preferred): High-dose PEG (1–1.5 g/kg/day) for 3–6 days 7
• Rectal route (if oral fails): Phosphate enemas may be used, though repeated use should be avoided 7
• Do NOT use mineral oil for disimpaction in infants due to aspiration risk 1

Dietary and Behavioral Modifications

• Increase fluid intake: Ensure adequate hydration to soften stools 1
• Trial of cow's milk elimination: Consider a 2-week trial, as cow's milk may promote constipation in some children 1
• Add fiber-rich foods: Fruits (prunes, pears, apricots), vegetables, and whole grains 1
• Avoid constipating foods: Bananas, rice cereal, and excessive dairy 2

Note: Hyperosmotic mineral water, diet alone, and endoanal medications are NOT effective treatments for established constipation 7

What NOT to Do

• Do NOT use stimulant laxatives (e.g., senna, bisacodyl) as first-line therapy in infants 1
• Do NOT rely on glycerin suppositories as the sole treatment—they provide only temporary relief 1
• Do NOT delay treatment waiting for spontaneous resolution; chronic constipation worsens with time 6, 2
• Do NOT assume constipation is benign without ruling out Hirschsprung's disease, especially if symptoms began in the neonatal period 1

When to Refer or Escalate

• Immediate referral if bilious vomiting, severe abdominal distention, or signs of obstruction are present 4
• Pediatric gastroenterology referral if:
  • Constipation began in the first month of life (concern for Hirschsprung's disease) 1
  • No response to 3–6 months of appropriate medical therapy 1
  • Recurrent fecal impaction despite maintenance therapy 7
  • Associated developmental delays or neurologic abnormalities 2

Follow-Up and Monitoring

• Reassess in 1–2 weeks after starting treatment to evaluate stool frequency, consistency (use Bristol Stool Chart), and pain with defecation 2
• Adjust PEG dose based on response: increase if stools remain hard or infrequent, decrease if diarrhea develops 7
• Long-term maintenance: Most children require 6–12 months of therapy; only 50–70% achieve long-term improvement 1
• Educate parents that functional constipation is a chronic condition requiring prolonged treatment and that early discontinuation leads to relapse 6, 7

Common Pitfalls

• Underdosing laxatives: The most common reason for treatment failure is insufficient dosing 7
• Stopping treatment too early: Maintenance therapy must continue for months to years to prevent relapse 1
• Misdiagnosing Hirschsprung's disease as functional constipation: Always consider Hirschsprung's if constipation began in the neonatal period or if there is failure to thrive 1
• Ignoring behavioral factors: Stool-holding behaviors perpetuate the cycle of constipation and must be addressed 6