ABDOMINAL WALL DEFECTS
(EXOMPHALOS & GASTROSCHISIS)
Types of Abdominal Wall Defects
- Omphalocele/Exomphalos: Congenital herniation of
abdominal contents at the umbilicus (i.e. into the umbilical
cord). Occasionally divided into:
- <4cm - umbilical cord hernia
- >4cm - omphalocele.
Rarely occurs above or below umbilicus (see below). N.B. Amniotic
sac (amnion & peritoneum) is always present but it may
have ruptured at or before birth exposing the contents.
- Gastroschisis: Full thickness abdominal wall defect
situated almost always to the right of the umbilicus
without a covering membrane. A bridge of skin separates it
from the umbilicus.
- Prune Belly Syndrome: Congenital deficiency of
abdominal musculature, urinary tract dilatation and
cryptorchidism. There are three grades:
- I. Severe renal and pulmonary disease incompatible with
- II. Severe uropathy requiring extensive reconstruction.
- III. Healthy neonates requiring little or no surgery.
- Others: e.g. Bladder extrophy.
Gastroschisis: 1:20,000 - 30,000
Prune Belly: 1:50,000
- Omphalocele: 30% have associated congenital defects (?
up to 50%).
- 20% have congenital heart disease, most commonly tetralogy.
- G.U.T., most commonly bladder extrophy.
- Beckwith-Wiedmann syndrome:
- Macroglossia (gigantism)
- In 50% pancreatic hyperplasia leads to
- Polycythemia with hyperviscosity is also common.
- Gastroschisis: Congenital associations are uncommon (?5
- 25%) but 22% are premature. The gut may be infarcted or
- Prune Belly: >90% have associated defects:
- Phimosis/meatal stenosis
- Megaureter (85%)
- Pulmonary hypoplasia (?due to mechanical effect of
- Dislocated hips
- Club feet
Abdominal wall and bowel develop conjointly over the 3rd to 12th
weeks in utero, final bowel fixation occurring after birth.
Week 3: the embryo has cephalic, caudal and lateral folds:
- mediastinal/thoracic contents
- Somatic layer defect causes the rare epigastric omphalocele
associated with diaphragmatic, thoracic wall and
- hypogastric abdominal wall
- Defects cause bladder extrophy or the rare hypogastric type
- lateral abdominal wall
- future umbilical ring
- Defects cause umbilical hernia or periumbilical
Weeks 4 - 10: Gut growth is faster than abdominal wall growth forcing
the gut into the cord.
Weeks 10 - 12: Gut returns to the abdomen with counterclockwise
Gastroschisis has been blamed on intrauterine disruption of the right
omphalomesenteric artery but it may be just a different expression of
the same defect that causes omphalocele.
The embryology of Prune Belly Syndrome is unknown.
- Heat loss from exposed abdominal contents.
- Fluid loss into & from exposed bowel (greater with
- Gastric distension.
- Associated malformations.
- Fluid management:
- excellent i.v. access mandatory.
- ?choice of fluid:
- loss is mainly isotonic with some protein
- logically Hartmanns + NSA best.
- may need 10 - 15ml/kg/hr + boluses.
- Heat management:
- usual problems of heat loss in neonates apply.
- Additional loss from bowel may be reduced by covering with
sterile wrap and towels or bowel bag (also helps to reduce
- Infection control:
- risk is reduced by covering bowel, prompt surgery and broad
- Gastric Distension:
- relieve with nasogastric tube.
- All need cardiac and respiratory review with
appropriate investigations and treatment of associated
- All children with omphaloceles need repeated
BSL's to exclude Beckwith-Wiedemann syndrome and hypoglycaemia.
Treatment is with glucose infusion 6 - 8mg/kg/min. Boluses may
cause severe rebound hypoglycaemia.
- First decision:
- Is the child fit for surgery at all?
- Depends on associated defect.
- If not then conservative management (used to be with
mercurochrome to promote eschar formation!).
- Second decision:
- Primary or staged closure?
- Staged closure used a silon pouch which is gradually
reduced in size ("reefed") then removed under G.A.
- Depends on whether or not exposed contents will fit back
into the abdomen.
- Decision may have to wait till during surgery.
- Based on:
- Size of defect:
- extremes are obvious
- small ones --> primary
- very big ones --> staged
- marginal ones more difficult, then based on:
- Surgical "preference":
- some prefer to attempt primary closure since the
prosthetic sac may dehiss and predispose to infection and
- others prefer staged since there is less risk of
dehiscence, marginal infarction, bowel
ischaemia/infarction, i.v.c. obstruction with hepatic and
renal ischaemia, and respiratory failure (primary closure
usually requires 24 - 48hrs ventilation).
- there doesn't seem to be much difference in outcome
between the two in truly marginal situations.
- Intra-op indications: --> all suggest changing to a
- difficulty with ventilation after closure
- measured gastric or bladder pressure > 20mmHg
- lower body swelling/oedema
- dusky wound margins
- Usual problems of neonatal anaesthesia:
- Compounded by:
- problems of prematurity when present - R.D.S.
- associated cardiac defects
- associated pulmonary hypoplasia
- increased heat and fluid loss
- hypoglycaemia in Beckwith-Weidemann
- ongoing fluid/protein/red cell resuscitation
- strict attention to heat preservation
- BSL monitoring when appropriate
- careful attention to respiratory function especially at
time of closure and afterwards. Should be hand ventilated
during closure. ?advisability of arterial line for sampling.
- watch for impaired cardiac function after closure due to
obstructed i.v.c. ?advisability of art line again.
- Additional problems:
- full stomach
- NG tube
- aspirate before induction
- awake intubation or rapid sequence.
- lower body congestion
- lines in upper body
- BP & SpO2 on upper limbs
- watch renal/hepatic function (may have reduced drug
- controversy over muscle relaxation, most arguing its
necessity but some saying it may make a marginal call a wrong
one (i.e. gets too tight when NDMR wears off).
- N2O not a good idea:
- question of post-op ventilation:
- bigger ones with primary closure
- associated defects
- Prune Belly with poor musculature
- marginals (probably yes)
- Big ones with pouch may be able to breath
spontaneously since the abdominal pressure is low. Some
suggest spont. resp. for final closure to assess if it's
- macroglossia/gigantism in Beckwith-Wiedemann may lead to
difficulty with airway/intubation.
- epidural has been suggested as best:
- good analgesia
- reduced abdominal and vascular pressures
- better respiratory function.