Workup for Chronic Constipation in a 3-Year-Old
For a 3-year-old with chronic constipation previously treated with lactulose, the workup should be minimal and focused on ruling out red flags through history and physical examination, as approximately 95% of childhood constipation is functional and does not require laboratory investigations. 1, 2, 3
Initial Clinical Assessment
History - Key Red Flags to Identify
- Onset timing: Constipation present since birth or delayed passage of meconium (>48 hours) suggests Hirschsprung disease and requires rectal biopsy 3
- Stool withholding behaviors: Look for severe withholding maneuvers (present in 97% of functional constipation), painful bowel movements with screaming (77%), and infrequent bowel movements (58%) 4
- Associated symptoms: Assess for abdominal distension, failure to thrive, vomiting, or neurological symptoms that suggest organic causes 3
- Dietary history: Evaluate fluid intake, fiber consumption, and excessive milk intake 5, 6
Physical Examination - Essential Components
- Digital rectal examination: Perform to identify fecal impaction in the rectum, assess anal tone, and evaluate for anatomical abnormalities 5
- Abdominal examination: Palpate for fecal masses and assess for distension 3
- Inspection: Check for anal fissures, perianal skin tags, or sacral dimples that may indicate spinal dysraphism 3
- Neurological examination: Assess lower extremity reflexes and strength if spinal cord pathology is suspected 3
Laboratory and Imaging Workup
When NO Red Flags Are Present (Functional Constipation)
No laboratory investigations or imaging studies are required for functional constipation in children. 3 The diagnosis is clinical, and testing does not change management or outcomes.
When Red Flags ARE Present
- Thyroid function tests: Order if signs of hypothyroidism (growth failure, delayed reflexes) 5
- Serum calcium and electrolytes: Check if hypercalcemia or hypokalemia suspected 5
- Celiac screening: Consider if poor growth or other gastrointestinal symptoms 3
- Abdominal radiograph: Only if fecal impaction cannot be determined clinically or if obstruction is suspected 3
- Rectal biopsy: Essential if Hirschsprung disease suspected (constipation from birth, absence of stool withholding, failure to thrive) 3
Common Pitfalls to Avoid
- Over-investigating functional constipation: The vast majority (90-95%) of cases are functional and do not benefit from extensive testing 1, 2, 3
- Missing fecal impaction: Impaction can present with overflow diarrhea, which parents may misinterpret as the constipation resolving 6
- Premature discontinuation of lactulose: Since this child was previously on lactulose, assess whether treatment was adequate in dose and duration before assuming treatment failure 4
- Ignoring toilet posture: Ensure the child has proper seating with buttock support, foot support, and comfortable hip abduction for effective defecation 5
Next Steps After Workup
If the workup confirms functional constipation (no red flags), switch from lactulose to polyethylene glycol (PEG) 3350 as first-line therapy, as PEG is superior to lactulose for stool frequency, stool consistency, and abdominal pain relief in children. 7, 5 Start with 0.8-1 g/kg/day with a goal of 2-3 soft, painless stools daily 5
If fecal impaction is present on rectal examination, perform disimpaction first using high-dose PEG (1.5 g/kg/day for 3-6 days) before starting maintenance therapy. 1, 3 Glycerin suppositories are an alternative for immediate relief if needed 6
Maintenance therapy typically requires many months before normal bowel motility returns, and families must understand this is a long-term treatment to prevent the 40-50% relapse rate seen with premature discontinuation 5, 4