Prevalence:

• 1 in 3,000 births.

Ultrasound diagnosis:

• The condition is characterized by congenital absence of intramural parasympathetic nerve ganglia in a segment of the colon. The aganglionic segment is unable to transmit a peristaltic wave, and therefore meconium accumulates and causes dilatation of the lumen of the bowel. The ultrasound appearance is similar to that of anorectal atresia, when the affected segment is colon or rectum.
• Polyhydramnios and dilatation of the loops are present in the case of small bowel involvement; on this occasion, it is not different from other types of obstruction.

Associated abnormalities:

• Chromosomal abnormalities, mainly trisomy 21, are found in 5% of cases.

Investigations:

• Detailed ultrasound examination.
• Amniocentesis for karyotyping or analysis of cfDNA in maternal blood.

Follow up:

• Ultrasound scans every 2-3 weeks to monitor the evolution of the condition and assess amniotic fluid volume. Amniodrainage may be necessary if there is polyhydramnios and cervical shortening.

Delivery:

• Place: hospital with neonatal intensive care and facilities for pediatric surgery.
• Time: 38 weeks.
• Method: induction of labor aiming for vaginal delivery.

Prognosis:

• Postnatal surgery is aimed at removing the affected segment and this may be a two-stage procedure with temporary colostomy. Neonatal mortality is approximately 20%. 

Recurrence:

• No increased risk of recurrence.
• Part of trisomy 21: 1%.