Abdominal Wall Defects: Omphalocele vs. Gastroschisis

Abdominal Wall Defects: Omphalocele vs. Gastroschisis
By:Joanna Thomson,
Surgery Clerkship

Embryology Review
* The Midgut gives rise to:
o Duodenum distal to the bile duct
o Jejunum
o Ileum
o Cecum
o Appendix
o Ascending colon
o Hepatic flexure of the colon
o Proximal two-thirds of transverse colon.

Physiological Umbilical Herniation
* As a result of rapid growth and expansion of the liver, the abdominal cavity temporarily becomes too small to contain all the intestinal loops.
* The intestinal loops enter the extraembyronic cavity within the umbilical cord during the sixth week of development.
* As herniation occurs, the loop undergoes a 90 degree counterclockwise rotation around the superior mesenteric artery.

Return to Abdominal Cavity
* During 10th week of development, herniated intestinal loops begin to return to the abdominal cavity.
* Undergoes additional 180 degree counterclockwise rotation about the superior mesenteric artery.
* Factors responsible for this return are not precisely known... It is thought that regression of the mesonephros (kidney), reduced growth of the liver, and expansion of the abdominal cavity all play roles.

Omphalocele
* Herniation of abdominal viscera through an enlarged umbilical ring.
o Failure of the bowel to return to the body cavity following physiological umbilical herniation. Defective mesodermal growth causes incomplete central fusion and persistent herniation of the midgut.
* Extruded viscera may include LIVER, small and large intestines, stomach, spleen, or bladder.
* Covered by amnion and peritoneum

Gastroschisis
* Herniation of intestinal loops through the anterior abdominal wall.
* Defect lateral to the umbilicus (right>left)
o Abnormal involution of the right umbilical vein or vascular accident involving the omphalomesenteric artery causes localized abdominal wall weakness.
* No sac covers the extruded viscera.

Prenatal Diagnosis
* Elevated maternal serum alpha fetoprotein
* Ultrasound
Omphalocele Gastroschisis

Epidemiology
* Prevalence:
o Omphalocele: 1/5,000 births
o Gastroschisis: 1/10,000 births
+ Increasing in frequency, especially in young women.
* Mortality:
o Omphalocele: 25%
+ Related directly to presence of chromosomal and other abnormalities
o Gastroschisis: <5%

Omphalocele Associated Anomalies
* Chromosomal abnormalities (50%)
* Neural tube defects (40%)
* Beckwith-Wiedemann syndrome
* Pentalogy of Cantrell

Gastroschisis Associated Anomalies
* Additional gastrointestinal problems
Initial Management
* Acute management aimed at maintaining circulation to bowel and preventing infection while stabilizing infant (temperature/fluids) :
o Cover the defect with sterile dressing soaked in warm saline to prevent fluid loss
o Nasogastric decompression
o IV fluids with glucose
o Antibiotics

Surgical Treatment
* Surgery performed to return the viscera to the abdominal cavity and close the defect.
o Primary Surgical Closure: Success dependent on size of the defect and size of the abdominal and thoracic cavities.

o Staged Closure: Gradual reduction of the contents into the abdominal cavity using an extra-abdominal extension of the peritoneal cavity (termed a silo) and using gentle pressure. Usually requires 1-3 weeks, after which the defect is then primarily closed.

Abdominal Wall Defects.ppt