Exomphalos

Exomphalos occurs when the baby’s abdominal wall does not fully develop while in the womb. The intra-abdominal organs herniate into the umbilical cord and the bowel does not sit inside the abdomen in the correct place.

• The intestines and abdominal organs are outside of the body to varying extents. The herniated abdominal contents are covered in a membrane consisting of an outer layer of amnion and an inner layer of peritoneum.
• The condition can be split into:
• • exomphalos minor: the opening is less than four centimetres, and the herniation contains only intestine; and
  • exomphalos major: the opening is greater than four centimetres and/or the herniation contains liver.

• Exomphalos is usually diagnosed during routine screening ultrasound investigation, at either 12 weeks or 20 weeks.
• In up to 50% of cases there may be problems in other systems, especially cardiac systems.
• It is important to perform ultrasound scans at an appropriate gestation point to check for exomphalos, because herniation of abdominal contents is physiological in early gestation.

The cause of exomphalos is unknown. However, it can be associated with:

• chromosomal anomalies, mainly trisomy 13 and trisomy 18, which can be linked to around 30%–50% of cases; and
• genetic syndromes, most commonly Beckwith-Wiedemann syndrome, which can be linked to around 10% of cases.

The chance of an underlying aneuploidy or genetic syndrome is greater where there are multiple anomalies.

Invasive testing, in the form of chorionic villus sampling or amniocentesis, can be performed in order to facilitate genomic testing.

Exomphalos itself is not an inherited structural anomaly, and isolated exomphalos has no increased recurrence risk. Where aneuploidy is diagnosed, there is a recurrence risk of around 1%.

Future recurrence risks may be increased where a genetic diagnosis is made. Recurrence with Beckwith-Wiedemann syndrome has a risk of up to 50%.

The management of exomphalos is multidisciplinary and depends on its severity, as well as the presence of any associated anomalies.

Antenatal management

Serial ultrasound scans are recommended every four weeks to assess growth and amniotic fluid levels.

The Sieme formula is used to calculate estimated fetal weight, as opposed to formulas that require the abdominal circumference.

Delivery

There is no contraindication to vaginal delivery. Mode of delivery should be decided based on obstetric risk factors.

Delivery should occur at around 38 weeks in a centre with neonatal support and paediatric surgery available. Caesarean section should be considered if the fetus is breech or if more than 75% of the liver is within the herniated sac.

Postnatal management

Exomphalos requires surgical management, via a single surgery or multiple surgeries. An underlying life-limiting genetic diagnosis and/or other serious comorbidities may, however, limit the options available for surgical repair.

For clinicians

• NHS England: National Genomic Test Directory
• Fetal Medicine Foundation: Exomphalos

References:

• Nitzsche K, Fitze G, Rüdiger M, Wimberger P and others. ‘Prenatal diagnosis of exomphalos and prediction of outcome‘. Scientific Reports 2021: volume 11, issue 8752. DOI: 10.1038/s41598-021-88245-0
• Poddar R and Hartley L. ‘Exomphalos and gastroschisis‘. Continuing Education in Anaesthesia Critical Care and Pain 2009: volume 9, issue 2, pages 48–51. DOI: 10.1093/bjaceaccp/mkp001

For patients

• Gov.uk guidance: Abdominal wall defects: Exomphalos information for parents
• Great Ormond Street Hospital for Children NHS Foundation Trust: Exomphalos