Omphalocele

Etiology

Omphalocele can be associated with several syndromes; the most common is Beckwith-Wiedemann syndrome. Beckwith-Wiedemann syndrome is an overgrowth syndrome characterized by macrosomia, enlarged tongue, neonatal hypoglycemia, ear creases and pits, hemihypertrophy, visceromegaly, umbilical hernia, embryonal tumors, omphalocele, nephrocalcinosis, medullary sponge kidney disease, cardiomegaly, and nephromegaly. Traditionally, macrosomia, macroglossia, and hypoglycemia are noted in the neonatal period. Hemihyperplasia is noted in segmental regions of the body or specific organs.[3] Developmental and cognitive outcomes are typically normal. Patients with Beckwith-Wiedemann syndrome have an increased risk of cancer during the first eight years of life with embryonal tumors such as neuroblastoma, hepatoblastoma, and Wilms tumor. These embryonal tumors have a higher cure rate when diagnosed early, making screening paramount for prevention. Screening for hepatoblastoma is performed by measuring serum alpha-fetoprotein every 3 months until 4 years of age, and screening for Wilms tumor is done every 3 months through 8 years of age with a complete abdominal ultrasonography.[4]

Other syndromes associated with omphalocele include the following:

• Trisomy 13 (Patau syndrome): Small eyes, cleft lip and palate, microcephaly, cryptorchidism, polydactyly, hypertelorism, micrognathia, cutis aplasia, and external ears anomalies.[5]
• Trisomy 18 (Edwards syndrome): Dolichocephaly, external ear anomalies, micrognathia, short palpebral fissures, small face, clenched fist with overriding fingers, hypotonia, and rocker bottom feet.[6]
• Trisomy 21 (Down syndrome): Hypotonia, upslanting palpebral fissures, brachycephaly, low set ears, single palmar crease, flat nasal bridge, Brushfield spots around the iris, in-curved fifth digits, and a gap between the first and second toes.[7]
• Pentalogy of Cantrell: Ectopia cordis, midline supraumbilical abdominal defect, sternal cleft, and intracardiac defect.[7] 
• Shprintzen-Goldberg syndrome: Craniosynostosis, dolichocephaly, hypertelorism, exophthalmos, strabismus, elongated fingers and limbs, umbilical and abdominal hernias.[8]
• Charge syndrome: Coloboma, heart defect, choanal atresia, growth or developmental retardation, genital abnormality, and ear anomalies.[7]
• Cloacal exstrophy (OEIS) syndrome: exstrophy of the bladder, imperforate anus, spinal defects.[9]
• Carpenter syndrome: Kleeblattschadel skull deformity (trilobed cloverleaf skull) from pancraniosynostosis, syndactyly in the hands and feet, and mental retardation.[7]
• Marshall-Smith syndrome: Prominent forehead, shallow orbits, blue sclerae, depressed nasal bridge, micrognathia, accelerated skeletal maturation, respiratory difficulties, mental retardation.[7]
• Meckel-Gruber syndrome: Occipital encephalocele, cleft lip and palate, microcephaly, microphthalmia, abnormal genitalia, polycystic kidneys, and polydactyly.[7]

Epidemiology

The prevalence of omphalocele in the United States is 1.86 per live births.[10] This prevalence increased by 11% between 1999-2001 and 2005-2007. Omphalocele appears to develop more frequently in women of extreme reproductive age (less than 20 and more than 40 years of age). Omphalocele occurs more commonly in black compared to white persons. Multiple births and male sex also have been associated with omphalocele. 

Pathophysiology

Disturbance of organogenesis during the embryonic period results in omphalocele. Around the sixth week of development, the abdominal contents become too large to be contained in the abdominal cavity and protrude at the base of the umbilical cord. This event is known as physiologic midgut herniation and is easily identified on prenatal ultrasound between the 9 and 11 weeks of gestation. The liver is never present in the physiologic midgut herniation. By 12 weeks of gestation, the hernia reduces, and when it persists, it is no longer physiological. Omphalocele occurs when the gut contents fail to rotate and return to the abdominal cavity. It can occasionally contain the liver in the presence of a large abdominal wall defect.

In general, omphaloceles are associated with advanced maternal age and are known to occur in twins.

History and Physical

The diagnosis of omphalocele postnatally is evident on physical examination upon the identification of an anterior midline abdominal mass at the site of the umbilical cord insertion covered by a membrane. The omphalocele can be small with only a few loops of intestines protruding through the defect, large containing several abdominal organs, or giant when the defect is greater than or equal to 5 centimeters with the liver partly protruding. Restrictive lung disease is common in these infants, and thus it is vital to stage the repair.

Evaluation

Prenatal diagnosis is based on ultrasound that can detect almost all omphaloceles by the end of the first trimester and elevated maternal serum alpha-fetoprotein concentration. All infants with omphaloceles should be worked up to rule out congenital disorders like Beckwidth Wideman syndrome or Prader Willi syndrome.

Treatment / Management

The management of neonates born with omphalocele consists of the initial steps of airway stabilization, sterile wrapping of the bowel to preserve heat to reduce insensible fluid loss, insertion of an orogastric tube for bowel decompression, and the establishment of peripheral intravenous access. In case of vascular compromise suggested by tachycardia, low blood pressure, or a dusky bowel appearance, the patient should be positioned left side down right side up.

Providers have to avoid placing dressings that are excessively wet or circumferential as they may macerate the omphalocele and compromise blood flow. 

After the initial steps, the subsequent management involves the administration of intravenous fluids and broad-spectrum antibiotics.

If a patient has a small omphalocele, surgical repair is an option within the first 72 hours of life via primary closure of the skin and fascia. Patients with other defects benefit from delayed closure after a silo is put in place in the first 24 hours of life. The silo is then progressively reduced over 3 to 7 days before the final closure of the defect. [1]

Closure of giant omphaloceles is a major undertaking, especially if it contains the liver. A patch is often used to close large wound defects.

Infants with omphalocele do tolerate oral feedings soon after the closure. Topical antibiotics are usually applied to the omphalocele until complete healing occurs.

Differential Diagnosis

Gastroschisis is the main differential diagnosis of omphalocele. In gastroschisis, the intestinal protrusion is usually to the right of the midline, and there is no involvement of the umbilical cord. The membranous sac is a major distinguishing feature of the two conditions as gastroschisis is characterized by free-floating bowel loops, but in the case of a giant omphalocele, the membrane can occasionally rupture in-utero. 

Other differential diagnoses include hernias of the umbilical cord with covered abdominal wall defects less than 2 cm, body stalk anomaly characterized by an umbilical cord absent or severely shortened associated with scoliosis.

Prognosis

The prognosis largely depends on the size of the defect and associated congenital anomalies and syndromes. As such, large omphalocele with associated abnormalities have a higher mortality rate. Also, neonates with liver protrusion through the defect appear to have a poorer prognosis. The overall survival rate is close to 80%, which reflects the efficacy of prenatal diagnosis and the decision taken by many families to terminate pregnancies with severe anomalies. [11]

Complications

Omphalocele complications can be categorized according to their time of occurrence. Prenatally and during delivery, the omphalocele may rupture, and in the case of a giant omphalocele, the liver can be injured. The majority of infants with omphalocele have a small thorax with varying degrees of pulmonary hypoplasia. Thus, mechanical ventilation is often required for weeks or even months until the lungs mature.

Infants with omphaloceles often need parenteral nutrition, which can lead to cholestasis and hepatomegaly. Thus, large omphaloceles need a staged repair. Tracheostomies are often needed until the lung mature.

Postnatally and after surgical repair, the complications consist of feeding difficulties, failure to thrive, inguinal hernias, gastroesophageal reflux, and occasionally esophagitis. Compared to gastroschisis, omphaloceles carry much higher mortality.