≥95% of pediatric constipation is functional. Always exclude organic causes in infants < 1 mo (Hirschsprung), with failure to thrive, bilious vomiting, abdominal distention, or delayed meconium passage > 48 h.
🚩 Red-flag clues (must not miss)
- •Delayed meconium > 48 h after birth = Hirschsprung
- •Bilious vomiting + abdominal distention = obstruction
- •Empty rectal vault on exam = Hirschsprung
- •Failure to thrive + constipation = organic etiology
- •Sacral dimple, tuft of hair = tethered cord / spinal dysraphism
History
- Stool frequency, consistency (Bristol scale), pain, blood
- Age of onset (birth = organic), toilet training history
- Diet, fluid intake, school avoidance of bathroom
- Medications (opioids, anticholinergics, iron)
Exam
- Abdomen: distention, palpable stool LLQ
- Perianal: fissures, position of anus, sacral dimple, hair tuft
- DRE only if organic suspected (empty vault → Hirschsprung)
- Lower extremity reflexes / tone for spinal cord pathology
Labs
- Usually none for functional
- If organic suspected: TSH, Ca, lead, celiac panel
Imaging
- KUB only if obstruction or fecaloma suspected
- Contrast enema / rectal biopsy if Hirschsprung
Differential & next step
| Diagnosis | Clue | Next step |
|---|---|---|
| Functional constipation | Onset > 1 y, withholding posture | Disimpaction + maintenance laxative |
| Hirschsprung disease | Delayed meconium, empty rectal vault | Surgery consult, contrast enema, rectal biopsy |
| Hypothyroidism | Growth failure, cold intolerance | TSH, free T4 |
| Cystic fibrosis (DIOS) | Known CF, RLQ mass | Gastrografin enema |
| Spinal dysraphism | Sacral dimple, abnormal reflexes | MRI lumbar spine (with & without contrast) |
| Anal stenosis / anteriorly displaced anus | Visible on exam | Pediatric surgery referral |
Medications & dosing
| Drug | Dose | Notes |
|---|---|---|
| PEG 3350 (MiraLAX) — disimpaction | 1–1.5 g/kg/day PO × 3–6 days (max 100 g/day) | |
| PEG 3350 — maintenance | 0.4–0.8 g/kg/day PO daily, titrate to 1 soft stool/day | |
| Glycerin suppository (infant) | 1 suppository PR PRN | Safe < 1 yr where PEG less validated |
| Lactulose | 1 mL/kg PO BID | Alternative to PEG; safe in infants |
| Mineral oil | 1–3 mL/kg/day PO | Avoid < 1 yr (aspiration), neuro impaired |
Management / next steps
- Disimpact (oral PEG preferred) — confirm clearance before maintenance
- Maintenance laxative for ≥ 3–6 months, weaned slowly
- Behavioral: scheduled toilet sits, dietary fiber + fluids
- Refer GI if refractory or red flags present
Source: https://fprmed.com/fprmedcom/Pages/Pedi/Constipation.html
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