💩 Chapter 16: Constipation

Nelson's Pediatric Symptom-Based Diagnosis | Functional Constipation · Hirschsprung Disease · Encopresis · Toilet Training · Disimpaction · Maintenance Therapy

🔍 Constipation in Children: Key Concepts

📊 Definition & Rome IV Criteria
Infant/Toddler: ≤2 defecations/week, painful/hard stools, fecal incontinence, retentive posturing, large fecal mass. Child/Adolescent: similar + toilet training >4 years. Functional constipation is most common.
🔄 Functional Constipation
Trigger: painful stool → withholding behavior → larger/harder stools → more pain → cycle. Symptoms: large-diameter stools, abdominal pain, overflow incontinence (encopresis), poor appetite. Normal growth, normal exam (except fecal impaction).
⚠️ Hirschsprung Disease (HD)
Absence of ganglion cells (rectum → proximal). Delayed passage of meconium (>48h), failure to thrive, enterocolitis. Rectal exam: tight sphincter, empty ampulla, explosive stool after withdrawal. Diagnosis: rectal suction biopsy (absence of ganglion cells).
💧 Encopresis (Fecal Incontinence)
Overflow incontinence from chronic constipation. Child passes small amounts of liquid stool around impacted mass. Not voluntary. Treatment: disimpaction then maintenance laxatives.
🧬 Organic Causes (Red Flags)
Hirschsprung, spinal cord anomalies (tethered cord, spina bifida), hypothyroidism, celiac disease, cystic fibrosis (meconium ileus), anal stenosis, medications (opioids, anticholinergics).
🚩 Red Flags for Organic Constipation
Delayed meconium (>48h), ribbon stools, failure to thrive, fever, vomiting, abdominal distention, perianal fistula, sacral dimple/tuft, lower extremity weakness, family history of Hirschsprung.

💡 Key Takeaway: Functional constipation is most common. Red flags for Hirschsprung: delayed meconium, failure to thrive, empty rectum on exam. Treatment: disimpaction (oral/rectal) + maintenance (polyethylene glycol).

🩺 Clinical Approach to Constipation: Step-by-Step Algorithm

🔹 Step 1: Differentiate functional from organic
• Functional: onset after infancy, large stools, retentive posturing, overflow incontinence, normal growth.
• Organic (Hirschsprung): delayed meconium, ribbon stools, FTT, empty rectum on exam, explosive stool after withdrawal.
🔹 Step 2: Assess for red flags (Hirschsprung, spinal, metabolic)
• Delayed meconium >48h, ribbon stools, FTT, fever, vomiting, abdominal distention.
• Sacral dimple/hair tuft, lower extremity weakness/reflex changes → spinal MRI.
• Hypothyroidism: jaundice, hypotonia, macroglossia.
🔹 Step 3: Physical exam including anorectal
• Inspect perianal area (fissure, fistula, skin tags).
• Palpate abdomen for fecal mass.
• Digital rectal exam: tone, stool in ampulla (functional), empty ampulla with tight sphincter (Hirschsprung), explosive stool after withdrawal.
🔹 Step 4: Diagnostic testing (if red flags)
• Abdominal X-ray: fecal loading.
• Contrast enema: transition zone (Hirschsprung).
• Anorectal manometry: absence of rectoanal inhibitory reflex (Hirschsprung).
• Rectal suction biopsy: gold standard for Hirschsprung (absence of ganglion cells).
🔹 Step 5: Treatment of functional constipation
• Disimpaction: oral (polyethylene glycol 3350 1-1.5 g/kg/day x 3-6 days) OR rectal (enemas).
• Maintenance: polyethylene glycol (0.4-0.8 g/kg/day), titrate to daily soft stools.
• Behavior: scheduled toilet sitting (5-10 min after meals), reward system.
• Diet: increased fiber, fluids, avoid constipation-promoting foods (bananas, cheese, excessive milk).