Gastrointestinal tract

Prevalence:

• 1 in 1,000 fetuses at 20 weeks’ gestation.

Ultrasound diagnosis:

• Small or absent gallbladder.
• In most cases this is a transient finding (75%), but some are due to isolated gallbladder agenesis (15%), cystic fibrosis (10%) and rarely biliary atresia (3%).

Associated abnormalities:

• In about 25% of cases of biliary atresia there associated heterotaxy syndrome, which includes situs inversus, polysplenia, malrotation of the gut intestinal atresia and heart defects.

Investigations:

• Detailed ultrasound examination.
• Amniocentesis: DNA studies for cystic fibrosis if both parents are carriers.
• Limited data suggest that in biliary atresia there are very low levels of digestive enzymes in amniotic fluid at <24 weeks’ gestation.

Follow up:

• Follow-up should be standard.

Delivery:

• Standard obstetric care and delivery.

Prognosis:

• Biliary atresia is a serious condition requiring liver transplantation.
• Gallbladder agenesis is a benign condition.

Recurrence:

• No increased risk of recurrence.