Delay in the elimination of meconium

Specialty: Pediatrics.

• Meconium delay
• Hirschsprung's suspicion
• meconium plug

Why it occurs

• Hirschsprung disease (congenital aganglionic megacolon due to failure in the migration of neural crest cells)
• Meconium plug or meconium ileus (obstruction of the intestinal lumen by thick meconium, frequently associated with cystic fibrosis)
• Congenital hypothyroidism (slowing of metabolism and intestinal peristalsis due to thyroid hormone deficiency)
• Hypoplastic left colon syndrome or extreme prematurity (neuromuscular immaturity of the distal colon)
• Maternal medication during childbirth (use of magnesium sulfate or opiate analgesics that depress neonatal transit)

Initial workup

Simple abdominal x-ray in standing or recumbent position (to assess air-fluid levels and absence of distal air). Opaque enema with water-soluble contrast (to identify the caliber-narrow transition zone in Hirschsprung or to attempt therapeutic resolution of the meconium plug). Rectal aspiration biopsy (gold standard for confirming Hirschsprung by demonstrating the absence of ganglion cells and hypertrophy of cholinergic nerve fibers with acetylcholinesterase staining). Neonatal metabolic screening and thyroid function tests (TSH and free T4). Sweat test or genetic study of the CFTR gene mutation if cystic fibrosis is suspected.

Standard management

• Diluted water-soluble contrast enema — like Gastrografin, it exerts an osmotic effect that lubricates and facilitates the expulsion of meconium plugs; should be used under strict hydroelectrolyte monitoring
• Levothyroxine sodium — specific replacement treatment if congenital hypothyroidism is confirmed; starting dose 10 to 15 mcg/kg/day orally
• Parenteral hydration solutions (to maintain hemodynamic stability and electrolyte balance before any surgical intervention).