Omphalocoele

Omphalocoeles, or exomphalos, are congenital midline abdominal wall defects at the base of the umbilical cord insertion with herniation of gut (or occasionally other content) out of the fetal abdomen.

The estimated occurrence can be up to 1:4000 of live births 3

It is typically a large defect through which liver and/or bowel herniate, and is covered by a peritoneal membrane as well as amnion. The umbilical cord typically inserts at or near the apex. 

General pathogenesis includes teratogenic effects by early pregnancy use of antithyroid drugs 10 .

A midline herniation is normal in a fetus until around gestational age 11-12 weeks.

Aetiology

Some suggest that the formation of an omphalocele may be due to failure of the medial segments of the two lateral embryonic wall folds to fuse at approximately 3-4 weeks post conception. This defect at the umbilical ring allows the abdominal content to herniate into a sac comprised of an outer layer of amnion and an inner layer of peritoneum and often Wharton's jelly

Genetics

Isolated cases are often sporadic.

Associations 

Associated anomalies are high (27-91% 7) and are thought to be even commoner with smaller omphalocoele containing bowel only 4.

Such anomalies include:

Serological markers
Antenatal ultrasound
  • multiple bowel loops (and on occasion liver) herniate into a membrane-covered defect (i.e. not free flowing) 
  • the umbilical cord insertion is directly into the omphalocoele
  • may also show evidence of polyhydramnios 
  • the abdominal circumference may be smaller as a result 
  • an allantoic cyst is often present
Plain radiograph
  • the bowel loops are covered by a membrane and cannot, therefore, be individually resolved
CT 
  • allows direct visualisation of herniation content +/- evidence of any malrotation
MRI
  • as with CT, allows better direct visualisation
  • the herniated liver is often of low T2 signal and the bowel of high T2 signal

The word omphalocoele is derived from the Greek words "omphalos" (Ομφαλός) meaning naval, and "cele"meaning pouch 6.

An omphalocele is associated with a higher morbidity and mortality than a gastroschisis, primarily due to a higher incidence of associated congenital anomalies. Smaller omphaloceles are thought to carry a worse prognosis due to increased risk of associated abnormalities.

Mortality rates can approach 80% when associated anomalies are present and increases to ~100% when chromosomal or cardiovascular anomalies exist. However, if found in isolation, then the associated mortality rate decreases to ~10% 3.

For imaging appearances consider:

  • pseudo omphalocele
  • gastroschisis: smaller para-umbilical defect usually to the right of midline, usually containing only bowel loops and not covered by a membrane
  • physiological gut herniation: this diagnosis should only be entertained in early pregnancy prior to 11.4 weeks or in gestation with crown lump length less than 44 mm. The physiologic midgut herniation should not exceed 7 mm in diameter
  • limb-body wall complex: large defect usually to the left of midline
  • umbilical hernia: abdominal wall hernia
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Article Information

rID: 1774
Synonyms or Alternate Spellings:
  • Omphalocele
  • Exomphalos
  • Omphaloceles
  • Omphalocoeles

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Cases and Figures

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    Figure 1: omphalocoele - macroscopic pathology
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    Case 1
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    Omphalocele
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    Case 5
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    Omphalocele

Abortus
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    Case 9
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