Omphalocele (ORPHA:660)
A rare, non-syndromic, abdominal wall malformation characterized by a hernia of the abdominal wall, centered on the umbilical cord, in which the protruding viscera are protected by a sac.
Epidemiology
In Europe, the prevalence at birth of omphalocele (isolated and syndromic forms combined) is estimated at about 1/8,000 births. At least half of patients have other abnormalities associated.
Clinical description
Omphalocele occurs very early in development and is typically detected prenatally. The hernia occurs at the umbilical ring allowing protrusion of the abdominal organs (midgut, liver, spleen and gonads) through the umbilical cord. The protruding viscera is encased in a sac consisting of three layers: the outer amniotic layer, a middle layer of Wharton's jelly and the inner peritoneal layer. The defect is classified based in the predominant location (epigastric, umbilical or hypogastric) and further classified into small, giant and ruptured. A small omphalocele is less than 5 cm with a sac that may contain a few intestinal loops. A giant omphalocele is greater than 5 cm with a whole or large part of the liver and bowel protruding. Membrane rupture, resulting in evisceration, can occur in utero, during delivery or postnatally, although it is a rare complication. Almost half of patients with omphalocele have other malformations associated, including cardiac, gastrointestinal, genitourinary, musculoskeletal and central nervous system malformations.
Etiology
While the exact pathogenic mechanism of omphalocele is unknown, there is a wide consensus that it is due to the defective closure of the abdominal wall in the embryo before 9 weeks of gestation.
Diagnostic methods
Diagnosis is usually made before birth by ultrasound, and can be detect as early as 11 to 14 weeks gestation in tertiary level referral centers. Associated malformations can then be sought for and management of the infant can be timely prepared in specialized units.
Differential diagnosis
Differential diagnosis includes gastroschisis, especially when the covering sac is damaged, and other celosomias that can be associated. Omphalocele can be part of polymalformative syndromes including Beckwith-Wiedemann syndrome, and trisomy 13, 18 or 21.
Antenatal diagnosis
Prenatal diagnosis is usually made in the first trimester. Fetal karyotype must then be assessed, and accurate screening for associated malformations has to be repeated along pregnancy.
Management and treatment
Management is surgical and aims to close the abdominal opening and return the protruding viscera to the abdomen. Various techniques can be applied when primary closure is not possible.
Prognosis
The prognosis for isolated omphalocele depends on the size of the defect; prognosis for small omphalocele is very good; however, giant omphalocele have a risk of pulmonary hypoplasia. Recent improvements to resuscitation and surgical techniques (through abdominal prostheses) have notably improved the prognosis of giant isolated omphaloceles, who present with some degree of pulmonary hypoplasia, over the last three decades. In syndromic cases, the main prognostic factor is the associated anomalies, especially cardiac defects.

                            Last update: 
                            March 2020


                            - Expert reviewer(s): 
                            Dr Sylvie BEAUDOIN