What are the next steps for managing constipation in an 8-year-old child who has not responded to lactulose (a non-absorbable sugar used as an osmotic laxative)?

Management of Constipation in an 8-Year-Old After Lactulose Failure

Switch to polyethylene glycol (PEG) 3350 as the first-line alternative, as it is more effective than lactulose for pediatric functional constipation and is the preferred osmotic laxative for children over 1 year of age. 1, 2

Immediate Next Steps

First: Rule Out Fecal Impaction

• Perform a digital rectal examination to assess for impaction 3
• If examination is equivocal, obtain a plain abdominal radiograph 3
• Red flags requiring immediate referral: fever, vomiting, severe abdominal pain, peritoneal signs, or complete obstruction 3

If Impaction is Present: Disimpaction Protocol

• High-dose PEG 3350 disimpaction regimen: 1-1.5 g/kg/day (up to 17g in 8oz water every 2-4 hours) for 3-6 days until disimpaction occurs 3, 4, 5
• Alternative: Phosphate enemas (age-appropriate dosing) can be used for rapid disimpaction 4, 5
• Add bisacodyl 5-10mg orally once daily as adjunct stimulant therapy during disimpaction 3, 2

If No Impaction: Maintenance Therapy

Primary recommendation: Start PEG 3350

• Dosing: 0.4-0.8 g/kg/day (typically 8.5-17g daily for an 8-year-old), adjusted to produce 1-2 soft stools daily 1, 2, 5
• PEG is superior to lactulose with better tolerability and fewer side effects (less bloating/gas) 1, 2
• Continue for months to years as functional constipation commonly relapses 5

Alternative osmotic laxatives if PEG unavailable:

• Magnesium hydroxide (milk of magnesia): 1-3 mL/kg/day divided once or twice daily 6, 5
• Avoid in renal insufficiency due to hypermagnesemia risk 7

Adjunct stimulant laxatives for rescue or combination therapy:

• Bisacodyl 5mg orally once daily or senna 8.6-17.2mg once daily 7, 2
• Use short-term (≤4 weeks continuous) or as rescue therapy, though longer use is likely safe 7
• Common side effects: abdominal cramping and diarrhea 7, 2

Behavioral and Dietary Modifications

Toilet training and behavioral interventions:

• Scheduled toilet sitting after meals (5-10 minutes) to utilize gastrocolic reflex 1, 5
• Proper toilet positioning with footstool support 4
• Behavioral education improves treatment response 5

Dietary considerations:

• Increase fluid intake 7
• Add dietary fiber if adequate fluid intake is maintained 7, 5
• Consider 2-4 week trial of cow's milk elimination, as dairy may promote constipation in some children 5

Common Pitfalls to Avoid

• Do NOT continue inadequate therapy - if lactulose failed, switching to another agent is essential 3
• Do NOT use docusate (stool softener) - it is ineffective and should be discontinued 3
• Do NOT underdose or discontinue too early - treatment requires sufficient doses for prolonged periods (months to years) 4, 1, 5
• Do NOT forget disimpaction first - maintenance therapy will fail if impaction is present 4, 1, 5

Long-Term Management

• Follow-up is critical: Only 50-70% of children show long-term improvement despite treatment 5
• Continue maintenance laxatives for minimum 2 months after regular bowel pattern established, then taper slowly 1, 5
• Relapse is common; reinitiate therapy promptly if constipation recurs 1, 5
• Consider referral to pediatric gastroenterology if refractory to conventional treatment after 3-6 months 6, 4