INTRODUCTION

In an exomphalos some of the abdominal contents are found outside the abdomen in a thin clear sac to which the baby's umbilical cord is attached. The sac consists of amnion and parietal peritoneum with some mesenchyme between. A small exomphalos may contain only a Meckel's diverticulum whilst a large defect may contain the stomach, liver and bladder. Non-rotation of the intestines is commonly seen.

Exomphalos is frequently associated with major abnormalities of other systems suggesting that this anomaly is not a simple failure of umbilical ring closure. The primary defect is likely to occur in early development. Most cases of exomphalos are sporadic, however the condition is often associated with aneuploidy and familial occurrence has been described. Exomphalos associated with macroglossia and macrosomia is known as Beckwith-Wiedemann syndrome.

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ANTENATAL

Most cases are identified by routine fetal anomaly scans and may be associated with elevated maternal serum alphafetoprotein (AFP) levels. On ultrasound the normal cord insertion is not seen but is replaced by a mass representing the bowel or liver herniating into the base of the umbilical cord. The mass encapsulated by a membrane is seen to be attached to the cord. Careful ultrasound examination will usually identify coexistent structural anomalies (especially cardiac anomalies) which exist in 70-85 % of fetuses.

Karyotyping should always be offered as at least 35% of fetuses have a chromosome abnormality. The presence of other abnormalities including aneuploidy will largely determine the prognosis. Frequently, a poor prognosis is predicted and termination of pregnancy requires discussion. Serial ultrasound measurements should be performed noting fetal growth if the pregnancy is continued.

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POSTNATAL

In cases with a normal karyotype and no major associated anomalies a vaginal delivery may be appropriate. Large lesions, especially containing liver are delivered by caesarean section. Detailed prenatal ultrasound may not identify all potential problems making a careful neonatal assessment vital in these cases. In choosing the place of delivery, consideration should be given to the availability of fetal medicine, neonatal and specialist surgical expertise.

With a small or medium sized exomphalos one operation to close the abdomen is all that is usually required. Sometimes the skin but not the muscles can be closed over an exomphalos sac and later operations are needed to close the muscles. If the sac is large, a silastic pouch can be used to allow progressive reduction of the bowel over a number of days before closure. Very large sacs can also be managed without operation. The sac can be painted with agents that lead to a scar forming, over which skin slowly grows. If skin alone has been used to cover the defect a ventral hernia results, and subsequent procedures are required to prepare this. Survival depends on the other defects and varies from 30-70%.

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WEST MIDLANDS DATA

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