Omphalocele
Omphalocele is a congenital herniation of viscera into the base of the umbilical cord, covered by a membranous sac. The incidence of omphalocele is approximately 1 in 4000 births.
GENETICS/BASIC DEFECTS
1. Embryogenesis: failure of the cranial, caudal, and lateral folds to fuse before myotome invasion is the most likely explanation for the failure of physiologically herniated midgut returning to the abdomen during the first trimester 2. Inheritance
a. Usually sporadic
b. Single gene disorders associated with omphalocele i. Autosomal recessive disorders
a) Agonadism with multiple internal malformation b) Agonadism, XY, with mental retardation, short stature, retarded bone age, and multi- ple extragenital malformations
c) Craniostenosis-mental retardation syndrome of Lin and Gettig
d) Hydrocephalus with associated malformation e) Hydrolethalus syndrome
f) Malpuech facial clefting syndrome
g) Omphalocele-exstrophy-imperforate anus- spinal defects (OEIS)
h) Omphalocele-cleft palate i) Opitz C syndrome ii. Autosomal dominant disorders
a) Beckwith-Wiedemann syndrome b) Omphalocele
c) Shprintzen syndrome iii. X-linked recessive disorders
a) Cranioorodigital syndrome b) Melnick-Needles osteodysplasty c) Omphalocele
d) Simpson-Golabi Behmel syndrome e) Thoracoabdominal syndrome
c. Other malformation syndromes associated with omphalocele
i. Caudal regression
ii. Cornelia de Lange syndrome iii. Amniotic band syndrome
iv. Limb body wall complex v. Megacystic microcolon vi. Schisis association vii. Skeletal dysplasias
d. Chromosome disorders associated with omphalocele (25%)
i. Trisomy 1q ii. Trisomy 3q iii. Trisomy 13 iv. Trisomy 18 v. Trisomy 21
vi. Trisomy 16 vii. add(15)
viii. Turner syndrome ix. Del(18p)
x. Del(21p)
xi. Diploid-triploid mixoploidy
CLINICAL FEATURES
1. General features a. Prematurity b. IUGR 2. Herniated sac
a. Size ranging from 2 to 10 cm
b. Covering avascular sac consists of fused layers of peritoneum and amnion
c. Contents of hernia include thoracic and abdominal viscera
i. Liver
ii. Large intestine iii. Small intestine
iv. Stomach v. Gall bladder vi. Urinary bladder vii. Pancreas viii. Spleen
ix. Internal genitalia
d. The sac may be torn or ruptured (10–20%)
e. Necrotizing enterocolitis and malabsortion only if sac is ruptured
3. Umbilical cord inserting into the apex of the sac
4. At increased risk for associated anomalies or syndromes (45–67%)
a. Cleft lip/palate
b. Gastrointestinal abnormalities i. Diaphragmatic hernia ii. Midgut volvulus iii. Meckel diverticulum
iv. Intestinal atresia v. Intestinal duplication vi. Intestinal malrotation vii. Colonic agenesis viii. Imperforate anus c. Congenital heart defects d. Neural tube defects e. Genitourinary
i. Exstrophy of the bladder f. Limb defects: absent radial ray g. Beckwith-Wiedemann syndrome
i. Macroglossia ii. Hypoglycemia iii. Organomegaly
iv. Gigantism 758
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h. Epigastric omphalocele associated with pentalogy of Cantrell
i. Cardiac abnormalities
a) Ventricular septal defect most common b) Occasional diverticulum of the left ventricle ii. Sternal cleft
iii. Omphalocele
iv. Anterior diaphragmatic hernia v. Ectopia cordis
5. Prognosis depending on:
a. Size of the omphalocele
i. Better prognosis with smaller defects
ii. Intractable respiratory insufficiency in newborns with large omphaloceles
b. Presence or absence of the associated anomalies c. Presence of chromosome anomalies
DIAGNOSTIC INVESTIGATIONS
1. Routine blood work 2. Abdominal radiography 3. Abdominal ultrasound 4. Echocardiography 5. Chromosome analysis
6. Initiate studies for associated single gene disorder or mal- formation syndrome
GENETIC COUNSELING
1. Recurrence risk: depends on the mode of transmission and associated chromosome anomalies
2. Prenatal Diagnosis
a. Elevated maternal serum alpha-fetoprotein b. Prenatal 2D ultrasonography
i. Maternal polyhydramnios
ii. A circumscribed mass containing liver and/or intestines at the cord insertion site
iii. Covering sac composed of amnion and peri- toneum
iv. Ruptured omphalocele: a rare complication v. Identifies other malformations and allows diag-
nosis of recognizable syndromes such as pental- ogy of Cantrell and prune-belly syndrome c. Prenatal 3D ultrasonography
i. A useful complement to 2D ultrasonography ii. Improved definition of omphalocele
iii. Identifies other malformations and allows diag- nosis of recognizable syndromes such as pental- ogy of Cantrell and prune-belly syndrome iv. Allows isolation and better evaluation of the
anomalous structure of interest when there is oligohydramnios or fetal contact with the uterine wall or placenta
d. Fetal echocardiography for evaluation of cardiac anomalies
e. Amniocentesis
i. Elevated amniotic fluid alpha-fetoprotein ii. Positive acetylcholinesterase
f. Chromosome analysis i. Amniocentesis
ii. CVS
iii. Fetal blood sampling 3. Management
a. Mode of delivery: currently no evidence to support a policy of cesarean delivery for infants with abdominal wall defects
b. Attempts at primary repair difficult due to a small abdominal cavity resulting from extra-abdominal location of the viscera in utero
c. Emergency care
i. Insertion of an orogastric tube a) To decompress the stomach
b) To prevent swallowed air from causing bowel distention
ii. Cover the intact omphalocele sac with a sterile dressing and protect it from injury
iii. Administer intravenous fluids and parenteral antibiotics
iv. Assess cardiorespiratory status and additional anomalies
d. Direct primary closure of the abdominal wall for small omphalocele (2 cm)
e. Staged closure, using a Dacron-reinforced Silastic silo as a temporary housing for the bowel for medium to large omphalocele
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Fig. 1. Two infants with omphalocele showing a sac containing bowel and other abdominal contents.
Fig. 3. A fetus with omphalocele showing the umbilical cord attaching to the apex of the sac.
Fig. 4. A neonate with a large ruptured omphalocele. The remnant of omphalocele sac is visible between the herniated viscera and the abdominal wall. The infant had body stalk anomaly.
Fig. 2. A 16-week-old fetus with omphalocele showing a sac contain- ing bowel.
