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.
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.
Isolated cases are often sporadic.
Associated anomalies are high (27-91% 7) and are thought to be even commoner with smaller omphalocoele containing bowel only 4.
Such anomalies include:
- chromosomal anomalies: can occur in 20-50% of cases; the risk of an associated chromosomal anomaly gets higher when the omphalocele is detected earlier in gestation
- other syndromic associations
- other fetal gastrointestinal anomalies: which confer a poor prognosis
- fetal CNS anomalies
- fetal cardiac anomalies: can occur in 50% of cases
- fetal genitourinary anomalies
- fetal skeletal anomalies
- 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
- the bowel loops are covered by a membrane and cannot, therefore, be individually resolved
- allows direct visualisation of herniation content +/- evidence of any malrotation
- as with CT, allows better direct visualisation
- the herniated liver is often of low T2 signal and the bowel of high T2 signal
History and etymology
The word omphalocoele is derived from the Greek words "omphalos" (Ομφαλός) meaning naval, and "cele", meaning pouch 6.
Treatment and prognosis
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
- 1. Reuter KL, Babagbemi TK. Obstetric and gynecologic ultrasound. Mosby Inc. (2006) ISBN:0323039766. Read it at Google Books - Find it at Amazon
- 2. Dähnert W. Radiology review manual. Lippincott Williams & Wilkins. (2007) ISBN:0781738954. Read it at Google Books - Find it at Amazon
- 3. Emanuel PG, Garcia GI, Angtuaco TL. Prenatal detection of anterior abdominal wall defects with US. Radiographics. 1995;15 (3): 517-30. Radiographics (abstract) - Pubmed citation
- 4. Getachew MM, Goldstein RB, Edge V et-al. Correlation between omphalocele contents and karyotypic abnormalities: sonographic study in 37 cases. AJR Am J Roentgenol. 1992;158 (1): 133-6. AJR Am J Roentgenol (abstract) - Pubmed citation
- 5. Daltro P, Fricke BL, Kline-fath BM et-al. Prenatal MRI of congenital abdominal and chest wall defects. AJR Am J Roentgenol. 2005;184 (3): 1010-6. AJR Am J Roentgenol (full text) - Pubmed citation
- 6. Georgiades CS. Etymology of selected medical terms used in radiology: the mythologic connection. AJR Am J Roentgenol. 2002;178 (5): 1101-7. AJR Am J Roentgenol (full text) - Pubmed citation
- 7. Blazer S, Zimmer EZ, Gover A et-al. Fetal omphalocele detected early in pregnancy: associated anomalies and outcomes. Radiology. 2004;232 (1): 191-5. doi:10.1148/radiol.2321030795 - Pubmed citation
- 8. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon
- 9. Axt R, Quijano F, Boos R et-al. Omphalocele and gastroschisis: prenatal diagnosis and peripartal management. A case analysis of the years 1989-1997 at the Department of Obstetrics and Gynecology, University of Homburg/Saar. Eur. J. Obstet. Gynecol. Reprod. Biol. 1999;87 (1): 47-54. Eur. J. Obstet. Gynecol. Reprod. Biol. (link) - Pubmed citation
- 10. Andersen SL, Olsen J, Wu CS et-al. Birth defects after early pregnancy use of antithyroid drugs: a Danish nationwide study. J. Clin. Endocrinol. Metab. 2013;98 (11): 4373-81. doi:10.1210/jc.2013-2831 - Pubmed citation