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An omphalocele or omphalocoele, also known as an exomphalos, is a rare abdominal wall defect. Beginning at the 6th week of development, rapid elongation of the gut and increased liver size reduces intra abdominal space, which pushes intestinal loops out of the abdominal cavity. Around 10th week, the intestine returns to the abdominal cavity and the process is completed by the 12th week. Persistence of intestine or the presence of other abdominal viscera (e.g. stomach, liver) in the umbilical cord results in an omphalocele.
Omphalocele occurs in 1 in 4,000 births and is associated with a high rate of mortality (25%) and severe malformations, such as cardiac anomalies (50%), neural tube defect (40%), exstrophy of the bladder and Beckwith–Wiedemann syndrome. Approximately 15% of live-born infants with omphalocele have chromosomal abnormalities. About 30% of infants with an omphalocele have other congenital abnormalities.
It is normal for the intestines to protrude from the abdomen, into the umbilical cord, until about the tenth week of pregnancy, after which they return to inside the fetal abdomen. The omphalocele can be mild, with only a small loop of intestines present outside the abdomen, or severe, containing most of the abdominal organs. In severe cases surgical treatment is made more difficult because the infant's abdomen is abnormally small, having had no need to expand to accommodate the developing organs.
Larger omphaloceles are associated with a higher risk of cardiac defects.
Post-surgery the umbilicus (navel) is deficient or abnormally placed that causes dislike amongst many patients. Umbilical reconstruction can be difficult due to scar tissue and lack of extra skin for surgical use, though this can be overcome by using Tissue expansion below the skin and umbilicoplasty.
Ultimately, prognosis depends on the size of the defect and whether associated abnormalities are present or complications develop. Morality and morbidities still occur, with the mortality rate for large omphaloceles with associated abnormalities being higher. Most surviving omphalocele infants have no-long-term problems and grow up to be normal individuals.
Beckwith–Wiedemann syndrome is also associated with omphaloceles.
By the fourth week of gestation the umbilical ring is formed. During the 6th week the midgut rapidly grows from the endoderm which causes a of the gut through the umbilical ring. The gut rotates as it re-enters the abdominal cavity which allows for the small intestine and colon to migrate to their correct anatomical position by the end of the 10th week of development. This process fails to occur normally in cases of exomphalos, resulting in abdominal contents protruding from the umbilical ring.
Gut contents fail to return to the abdomen due to a fault in myogenesis (muscle formation and migration during embryogenesis). During embryogenesis the mesoderm that forms muscle divides into several that migrate dorso-ventrally towards the midline. The somites develop three parts that are Somite which will form bone, dermatome which will form skin of the back and Somite which will form muscle. The that remain close to the neural tube at the back of the body have epaxial Somite, whilst the that migrate to the midline have hypaxial Somite. The hypaxial Somite forms the Abdomen. The Somite cells will give rise to Myocyte (embryonic ) which will align to form myotubules and then muscle fibers. Consequently, the Somite will become three muscle sheets that form the layers of abdominal wall muscles. The muscle of concern for exomphalos is the rectus abdominis. In the disease the muscle undergoes normal differentiation but fails to expand ventro-medially and narrow the umbilical ring which causes the natural umbilical hernia that occurs at 6 weeks of gestation to remain external to the body.
The location of the folding defect in the embryo determines the ultimate position of the exomphalos. A Head folding defect results in an Epigastrium exomphalos that is positioned high up on the abdomen which can be seen in the chromosomal defect pentalogy of Cantrell. Lateral folding defects result in a typical exomphalos that is positioned in the middle of the abdomen. A caudal folding defect results in a Hypogastrium exomphalos that is positioned on the lower abdomen.
Omphaloceles occurs more frequently with increased maternal age. Other related syndromes are Shprintzen Goldberg, pentalogy of Cantrell, Beckwith–Wiedemann and OEIS complex (omphalocele, exstrophy of the cloaca, imperforate anus, spinal defects).
After surgery a child with omphalocele will have some degree of intestinal malrotation. Due to intestinal malrotation 4.4% of children with omphalocele will experience a midgut volvulus in the days, months, or years after surgery. Parents of children with omphalocele should seek immediate medical attention if their child displays signs and symptoms of an intestinal obstruction at any point in their childhood to avoid the possibility of bowel necrosis or death.
Some experts differentiate exomphalos and omphalocele as 2 related conditions, one worse than the other; in this sense, exomphalos involves a stronger covering of the hernia (with fascia and skin), whereas omphalocele involves a weaker covering of only a thin membrane. Others consider the terms synonymous names for any degree of herniation and covering.
Surgery can be performed directly for small omphaloceles, which will require a short stay in the nursery department, or in a staged manner for large omphaloceles, which will require several weeks stay. Staged closure requires a temporary artificial holding sac (a silo) to be placed over the abdominal organs and sutured to the abdominal wall. This can be made of non-adhesive dressing. The silo is gradually reduced in size at least once daily until all of the viscera have been returned to the abdominal cavity. This is repeated for several days to a week until surgical closure of the fascia/skin can be done. Closure may require a patch that can be rigid or non-rigid and made of natural such as a bovine pericardium or artificial materials. The skin is then closed over the patch and it is re-vascularised by the body's liver blood vessels post-surgery. The staged surgery is required, as rushed reduction of the exomphalos compromises Vein return and ventilation, as it raises intra-abdominal pressure. In some cases, stretching of the abdominal wall to accommodate intestinal contents may be required. Non-operative therapy uses ointments. This is used for infants with large omphaloceles that have been born prematurely with respiratory insufficiency and associated chromosomal defects, as they would not be able to tolerate surgery. The ointment causes the sac to granulate and epithelialize, which leaves a residual large ventral hernia, which can be repaired later with surgery when the baby is more stable. After surgery, for larger omphaloceles, mechanical ventilation and parenteral nutrition is needed to manage the baby.
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