Omphalocele

An omphalocele (British English: omphalocoele) is a type of abdominal wall defect in which the intestines, liver, and occasionally other organs remain outside of the abdomen in a sac because of a defect in the development of the muscles of the abdominal wall.

Presentation
The sac, which is formed from an outpouching of peritoneum, protrudes in the midline, through the umbilicus (navel).

It is normal for the intestines to protrude from the abdomen, into the umbilical cord, until about the tenth week of pregnancy, after which they return to inside the fetal abdomen.

The omphalocele can be mild, with only a small loop of intestines present outside the abdomen, or severe, containing most of the abdominal organs. In severe cases surgical treatment is made more difficult because the infant's abdomen is abnormally small because it had no need to expand to accommodate the developing organs.

The presence of an omphalocele is often associated with cardiac defects.

Screening
An omphalocele is often detected through AFP screening or a detailed fetal ultrasound. Genetic counseling and genetic testing such as amniocentesis is usually offered during the pregnancy.

Causes
Some cases of omphalocele are believed to be due to an underlying genetic disorder, such as Edward's syndrome (Trisomy 18) or Patau Syndrome (Trisomy 13).

Related conditions
Gastroschisis is a similar birth defect, but in gastroschisis the umbilical cord is not involved and the lesion is usually to the right of midline. Parts of organs may be free in the amniotic fluid, and not enclosed in a membranous (peritoneal) sac. This condition is less commonly associated with other defects than omphalocele.

Other related syndromes are Pentalogy of Cantrell, Beckwith-Wiedemann, and OEIS Complex.