General features:
(1) visceral herniation through a central defect umbilical ring
(2) membranous covering composed of peritoneum and amniotic membrane
(3) the umbilical cord inserts onto the membranous sac
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Diameter
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Term
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< 4 cm
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hernia of the umbilical cord, small omphalocele
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4 - 6 cm
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medium omphalocele
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6 - 8 cm
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large omphalocele
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> 8 cm plus most of the abdominal viscera
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massive or giant omphalocele
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Contents may include:
(1) loops of small bowel
(2) portion of the liver
(3) other abdominal viscera (stomach, pancreas, spleen, urinary bladder, colon)
Associated anomalies
(1) cardiac (atrial septal defect, ventricular septal defect, patent ductus arteriosus, tetralogy of Fallot, bicuspid aortic valve, others)
(2) neurologic (anencephaly, hydrocephalus, spina bifida)
(3) small abdominal cavity, insufficient to contain the herniated viscera
(4) cleft palate
(5) urogenital defects (extrophy of bladder, extrophy cloaca)
(6) diaphragmatic hernia
(7) Beckwith-Wiedemann syndrome
(8) gastrointestinal (atresias, malrotation, imperforate anus)
Karyotype abnormalities (often a trisomy syndrome) are present in about a third of affected infants.
