THE FETUS WITH AN ABDOMINAL
Arlet G. Kurchubasche
Division of Pediatric Surgery and Program
in Fetal Medicine
Brown Medical School and Hasbro Children's Hospital
*Reproduced with permission
from Medicine & Health/Rhode Island 2001;84:159-161.
The May 2001 issue of this journal was published
in conjuction with the 2nd Annual Frank G. DeLuca Lectureship
in Pediatric Surgical Sciences, entitled "The Smallest Patient:
Foundations in Fetal Medicine," organized by the Brown Medical
School Program in Fetal Medicine
Antenatal detection of abdominal wall
defects has impacted the perinatal care of both the expectant
mother and of the fetus. Prenatal referral to tertiary care centers
that can provide for the surgical needs of the infant has also
allowed for focused management from the obstetric perspective
to identify the unique problems associated with these pregnancies.
With advances in maternal-fetal medicine, obstetrics and neonatal
surgery and the increasing availability of in utero interventions
it is essential to determine which current therapeutic interventions
result in optimized outcomes and where future investigational
efforts should be directed. In this age of information technology
we need to provide expectant parents with reliable and useful
Although not specifically elucidated,
the etiologies of omphalocele and gastroschisis are likely widely
discrepant, based not only on the spectrum of associated anomalies
in the fetus but also the differing demographics of the maternal
populations. This dichotomy extends to the postnatal period in
terms of operative management and morbidity and mortality. Vital
to appropriate counseling and stratification of risk therefore,
is the ability to make a specific diagnosis for a fetus with
an abdominal wall defect.
On sonogram, the presence of a defect to the right of the umbilicus,
with eviscerated bowel that is not contained within a membrane
is consistent with gastroschisis. The fetus with omphalocele
has an absent abdominal wall subjacent to the cord insertion
site with a membrane usually containing the protuberant liver
and eviscerated intestine. Localization of the defect is helpful
particularly to avoid diagnostic errors associated with the rare
ruptured omphalocele that masquerades as gastroschisis.
Approximately 20 % of anterior abdominal wall defects are omphaloceles.
Antenatal evaluation of the fetus with omphalocele focuses on
the associated conditions. These may include lethal chromosomal
anomalies (particularly trisomy 13 and 18), congenital cardiac
defects, other upper midline/thoracic defects such as in the
Pentalogy of Cantrell (sternal, diaphragmatic, pericardial defects
with ectopia cordis and omphalocele) or the lower midline OEIS
complex (omphalocele, exstrophy, imperforate anus, spinal defect).
Other associated conditions include Beckwith-Wiedeman syndrome,
cleft lip/palate and cryptorchidism. The incidence of associated
anomalies (excluding intestinal malrotation, which is uniformly
present in those with large defects) is reported as high as 69%.
In a recent study of 23 fetuses
or infants with the pre or postnatal diagnosis of omphalocele,
21 fetuses had an antenatal diagnosis made by 18 weeks gestation.2
In 18 pregnancies, the diagnosis was correct. (two false positives,
and 3 false negatives). Associated anomalies were correctly identified
in 12 but incorrectly reported in 8. There were 13 terminations
including 2 trisomy 18s and one trisomy 13. Two fetal deaths
followed amniocentesis. Of the 10 live births, 9 had their ventral
defect repaired with a one-year survival rate of 89%.
When providing antenatal counseling to parents, this information
needs to be relayed within the appropriate context. Those liveborn
infants with an omphalocele and without additional life-threatening
anomalies have a lesion that is amenable to surgical therapy
with good outcomes.
Repair of the omphalocele provides specific challenges to the
infant and surgeon, but in over 50% cases, a primary repair can
be achieved. The spectrum of defects ranges from the "hernia
of the cord", which could potentially be reduced and closed
at the bedside, to omphalocele minor with a fascial defect of
up to 4cm and to omphalocele major typically with defects from
4 cm to 8 cm. Given the closed nature of the defect, with liver
and intestines enclosed in peritoneum and amnion, postnatal management
can initially focus on the potentially lethal malformations.
Once these have been identified and addressed, usually within
24-48 hours, decisions can be made regarding surgical closure.
In contrast to gastroschisis, the intestinal tract is usually
normal, but the size of the defect and the liver may provide
major impediments to complete fascial approximation. Viscero-abdominal
disproportion refers to the discrepancy between the current abdominal
capacity and the extra-abdominal volume of eviscerated organs.
Aggressive reduction into the abdomen may result in compromised
hepatic or visceral perfusion requiring urgent decompression.
Infants with very large defects may require staged closure to
allow for gradual expansion of the abdominal wall. This may involve:
1) primary coverage with skin flaps with subsequent ventral hernia
repair, 2) staged closure using a silo, with or without excision
of the sac or 3) topical treatment may induce sufficient wound
contraction with epithelialization to achieve closure for subsequent
ventral hernia repair. Infants with lethal cardiac or chromosomal
disorders can be managed nonoperatively with topical therapy.
Extended hospital courses and complications are primarily limited
to those with defects measuring greater than 8 cm in diameter.
Even in this group the surgical mortality was only 8%.1 In the
absence of associated severe anomalies these infants can have
an uncomplicated course with a normal long-term quality of life.
Less optimal outcomes are determined primarily by the nature
of the chromosomal defect and the complexity of associated cardiac
and other organ system defects. With improvements in the reconstruction
of these complex anomalies, this will further reduce mortality
and improve quality of life. As such, the antenatal assessment
by a multidisciplinary team including perinatalogists, neonatologists,
geneticists and cardiologists and surgeons will have critical
impact on the decision to continue the pregnancy.
The perinatal management of infants with gastroschisis is quite
distinct from those with omphalocele. Whereas the size of the
ventral defect and associated anomalies dictate prognosis in
omphalocele, the relevant parameters in the infant with gastroschisis
are related to the condition of the newborn and the intestine.
Short bowel syndrome with its attendant risks remains one of
the significant complications of the diagnosis of gastroschisis.
Fetuses with gastroschisis tend to be small for gestational age
and are born to young primiparous women, often after preterm
labor. Although the specific factors leading to this congenital
malformation have not been elucidated, the focus has rested on
environmental and potentially nutritional factors. Studies from
the California birth defects monitoring program have proposed
that a low prepregnancy body mass may represent a risk factor
for offspring with gastroschisis. 3 These investigators suggest
that abnormal levels of 3 nutrients (low alpha carotene, low
total glutathione and high nitrosoamines) are potential candidates
for further investigation.4 Much of the clinical and basic science
investigation into gastroschisis has tried to identify factors
that contribute to the intestinal wall thickening and formation
of a peel over the serosal surface, the findings that most impede
reduction of the intestine into the abdominal cavity and that
are thought to contribute to the dysmotility encountered postoperatively.
Conventional wisdom attributes these changes to exposure to amniotic
fluid, although not all infants with gastroschisis exhibit the
serosal peel. A recent animal study has sought to differentiate
between urinary and gastrointestinal waste products in amniotic
fluid, and has implicated components of meconium as the more
significant sources of inflammation.5 Saline amnioinfusion performed
both in an animal model and in a small cohort of patients with
gastroschisis and severe oligohydramnios was found to be associated
with less inflammatory peel as compared to non-amnioinfused infants
with gastroschisis.6, 7,8 These concerns have been the premise
for advocating early delivery of these infants, particularly
when visceral distension is noted to be progressive, suggesting
an underlying intestinal obstruction. Vascular etiologies of
the intestinal atresias and of the inflammatory changes have
been proposed and may be related to constriction of the mesentery
by the approximating fascial edges as evidenced in fetuses born
with antenatal detection of gastroschisis and consequent jejunal
atresia or congenital SBS without abdominal wall defect. Based
on the premise that the amniotic insult to the intestine is cumulative
and a function of time - preterm induction of labor was considered
prudent so as to enhance the ability to achieve primary closure.
In the current literature, no randomized prospective series exists
to support this intervention and preliminary evidence from our
series of inborn patients in whom no attempt was made to induce
early labor suggests that there is no beneficial effect to early
delivery and that term infants recover as well if not better
than their preterm counterparts. Premature labor however, remains
a feature associated with gastroschisis and may not be an avoidable
event in approximately 30% of patients. 9 Debate in the perinatal
management of gastroschisis has also revolved around the mode
of delivery with Cesarean section advocated by multiple centers.
Vaginal delivery, however, has been shown to be safe in multiple
recent studies and general consensus would indicate that a trial
of labor is appropriate and that Cesarean section should be reserved
for obstetric indications only. 10,11,12
Antenatal counseling by a pediatric surgeon will focus on the
immediate surgical care to be delivered to an infant with exposed
viscera that are at risk for further vascular compromise. The
options for acute management range from operative intervention
either in the delivery room or in the operating room. The exposed
intestine has a variable degree of inflammatory peel. When extensive,
this may prohibit identification of an intestinal atresia. In
virtually all cases, the bowel length appears shortened, with
a thickened mesentery. Sedation and paralysis with expansion
of the lateral abdominal wall may enable complete reduction of
the viscera and permit fascial closure. If not feasible then
a silo, typically spring-loaded and no longer requiring fascial
sutures, can be inserted. This can also be accomplished at the
bedside with minimal sedation. A recent prospective trial of
routine insertion of a silo as compared to emergency operating
room closure provided favorable results for the routine insertion
of the silo with reduced number of days to extubation, to full
feeds and to home discharge. 13 The postoperative course of these
infants is typically marked by a prolonged ileus, during which
they rely on parenteral nutrition support. When intestinal continuity
has not become evident after several weeks, contrast studies
are performed to delineate the anatomy and to exclude the possibility
of an occult atresia. By this time much of the inflammatory peel,
which may have been present initially, will have resolved and
now allows for intestinal resection and anastomosis to establish
continuity. Short bowel syndrome may occur as a consequence of
atresias or after postnatal hypoperfusion insults to the intestine
or even florid necrotizing enterocolitis. With appropriate nutritional
management focusing on measures to avoid cholestasis, these infants
can be transitioned to full enteral feedings.
The use of promotility agents has not been shown to be useful
in expediting normal motility.12 Motility agents and acid suppression
therapy however may play a role in a significant number of infants
who have evident gastroesophageal reflux.14 Although both omphalocele
and gastroschisis are associated with intestinal malrotation,
the occurrence of gastroesophageal reflux during the first year
of life is reported to be higher in omphalocele than gastroschisis.
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