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CHAPTER 56

Congenital Anterior Abdominal Wall

Defects: Exomphalos and Gastroschisis

Iyekeoretin Evbuomwan
Kokila Lakhoo

Introduction the anterior wall of the chest (sternum, pericardium, and the heart,
Exomphalos and gastroschisis are the common forms of presentation of causing the classic features of the pentalogy of Cantrell). In the caudal
congenital abdominal wall defect. aspect of the anterior abdominal wall, the defect may be associated with
Exomphalos (from the Greek ex = out; omphalos = umbilicus) refers bladder exstrophy or varying degrees of anorectal anomalies. In the
to protrusion into the umbilicus. In its very mild form, a small loop female, there may be a cloacal anomaly. Other anomalies that have been
of intestine protrudes into the base of the umbilicus; this is a hernia described as being associated include trisomy 13, 18, or 21 anomaly
into the umbilical cord. In the more severe form, the defect allows and the Beckwith-Weidemann syndrome.
protrusion of small intestine and other viscera, pushing the umbilical The most common form is the central omphalocele, due to failure
cord forward and distending its base into a cystic mass containing the in the lateral folds. It may be classified in terms of shape, size,
viscera. This constitutes an omphalocele (from the Greek omphalos, content, whether there are associated other anomalies, and whether the
kele = hernia, tumour). Omphalocele is more common, with a general membrane coverage is intact or ruptured. More specifically:
incidence of 1:4,000 births. Omphalocele is a result of failure of 1. Shape:
formation and closing in of the anterior abdominal wall and could • Conical: includes hernia of the umbilical cord; usually small with
therefore be associated with other forms of impaired organ formation, broad skin edge diameter
which will determine the general prognosis.
Gastroschisis is a defect in the full anterior abdominal wall (from the • Globular: in which there is a large sac hanging on a relatively small
Greek gastro = stomach—the term generally used for abdomen; schisis diameter base and small abdominal cavity
= fissure, tear, or gape) through which the abdominal content protrudes 2. Size of defect:
into the amniotic cavity. • Small diameter up to 5 cm, described as minor
Gastroschisis occurs in 1:10,000 births; although this is less common
than exomphalos, in the Western world an increased incidence of • Diameter more than 5 cm, described as major
tenfold is noted in young mothers with substance abuse. Gastroschisis 3. Content of the sac:
is not due to or associated with impaired organ formation, but there
could be complications from mass protrusion of viscera through a small • Bowel loops only, small and large intestine sometimes on part of
defect, including vascular compromise, which in early foetal life could the stomach, bladder, and occasionally the ovary
result in bowel atresia. • Bowel loops and liver
Demographics 4. Associated with cardiac or other gross anomalies:
The estimated birth prevalence of omphalocele in western countries • Syndromic
is about 1 in 10, 000 births while that of gastroschisis is about 2.5 in
10, 000 births. The prevalence in sub Saharan Africa is not known • Nonsyndromic
as there are no population based studies. While the birth prevalence 5. Membrane coverage:
of omphalocele has remained generally stable over the years, reports • Intact
from industrialized countries (Europe, United States, Japan) indicate
that the rate for gastroschisis is on the increase. When omphalocele is • Ruptured membrane
associated with other abnormalities, the aetiology is multifactoral and For gastroschisis, a vascular accident of the right omphalomesenteric
incidence varies with age of the mother. These abnormalities occur artery and abuse of vasoactive drugs have been implicated in the aetiology.
more in younger mothers; omphalocele alone is more prevalent in older Clinical Presentation
mothers, however.
Omphalocele (Figure 56.1) is an obvious abnormality in the newborn,
Aetiology/Pathophysiology presenting as a mass arising from a defect in the anterior abdominal
The aetiology of these conditions is not known. For omphalocele, the wall covered by a membrane. The membrane is composed of an inner
pathogenesis is related to the formation of the anterior abdominal wall layer of peritoneum and an outer layer of amniotic membrane with
and return of the midgut into the abdominal cavity. At the third week Wharton’s jelly between. It is attached by its base circumferentially to
of gestation, three primitive divisions of the gut are identifiable as the skin of the anterior abdominal wall. The diameter of the base, the
foregut, midgut, and hindgut. By formation of the folds, intraembryonic content of the sac, and the size relative to the size of the abdominal
coelom becomes gradually separated from extraembryonic coelom. The cavity will influence the decision for the method of management. Also
fold initially consists of ectoderm and endoderm. The mesoderm later important are whether the membrane is intact or not all around the cir-
forms in between, and the folds close in on the umbilical cord and thus cumference and whether the membrane or part of it is infected.
complete the anterior abdominal wall. Failure of mesoderm develop- Other features to be examined are the possible associated congenital
ment results in defects. At the cranial portion, the defect could affect abnormalities. Such features as ectopia cordis, sternal defect, bladder