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Abdominal Wall Defect Repair
Omphalocele and Gastroschisis Repair

Omphalocele is similar to an umbilical hernia (See Pediatric Hernias). It is a larger defect of the umbilical ring into which the abdominal contents herniate. The size of these defects may be small with minimal bowel in the sac or large with the entire gastrointestinal tract and liver in the sac. Peritoneum covers the bowel. Gastroschisis is a defect of the abdominal wall usually to the right of the umbilical cord through which bowel herniates but there is no covering over the herniated bowel.

Anatomy

  • The mid abdominal wall is composed of two large muscles (rectus abdominis) that run up and down and originate from the rib cage above and insert into the pubic bone below (Figure 1)
  • The upper 3/4 of the rectus muscles are covered by a tough fascial sheath that lies in front and behind the muscles (Figure 2)
  • The lower ¼ of the rectus muscles has only a tough sheath in front of the muscle
  • The lateral abdominal wall muscles - external oblique, internal oblique and transverses abdominis muscles contribute to the sheath
  • The muscle sheaths meet in a midline band called the linea alba
  • Just below the middle of the linea alba is an opening called the umbilical ring where the umbilical cord entered the fetus
Figure 1 - Anatomy of the front wall of the abdomen. © C. Salici
Figure 2 - Anatomy of the front wall of the abdomen as seen from above. Note the various muscles (m) and fascia. © C. Salici

Pathology

  • An omphalocele (Figure 3) is a large defect of the umbilical ring into which the abdominal contents herniate covered only by a peritoneal sac
    1. The size of the defect may be small with minimal bowel in the sac or large with the entire gastrointestinal tract and liver in the sac
    2. The contents of the hernia are covered by the peritoneal lining of the abdominal cavity and the amnion (maternal placental tissue). There is no skin over the herniated structures
    3. The size of the defect may be small with minimal bowel in the sac or large with the entire gastrointestinal tract and liver in the sac
    4. Because the intestinal contents are in the hernia sac in utero (in the womb), the abdominal cavity fails to develop and is small
    5. Perforation of the hernia sac may occur with increase risk to the infant
    6. The defect may be discovered during fetal ultrasound examinations
    7. Other congenital anomalies are frequently present
  • Gastroschisis is an abdominal wall defect due to failure of the abdominal wall to develop just to the right of the umbilical ring (the most common site)
    1. All abdominal wall layers are missing including the peritoneum (Figure 4)
    2. The bowel herniates outside the abdomen without a covering. This creates two major problems
    • The abdominal cavity is underdeveloped (relatively small cavity) because of the extra abdominal location of bowel
    • The bowel has no peritoneal or skin coverage to protect it from the amniotic fluid which causes a chemical irritation of the peritoneum (peritonitis)
    1. There may also be a malrotation (abnormal position) of the bowel
    2. Other associated anomalies are fewer than with omphalocele
  • Strangulation (gangrene) of the bowel may occur
Figure 3 - The omphalocele is a large defect of the umbilical ring into which the abdominal contents herniate covered by a peritoneal sac but no skin. © J. Norah Figure 4 - With gastroschisis all abdominal wall layers are missing including the peritoneum. © J. Norah

History and Exam

  • These defects are present at birth and obvious to the observer
  • The herniated bowel is outside the peritoneal cavity with an abdominal wall defect at birth with (omphalocele) or without (gastroschisis) a peritoneal covering
  • The defect may be diagnosed with fetal ultrasound in utero

Tests

  • X-rays of the chest and abdomen are performed to rule out abnormalities of the chest and further evaluation of the abdomen
  • CT and MRI scans are occasionally obtained to better evaluate the conditions

Indication for Surgery

  • Surgery is performed as soon as the baby is stable

Surgical Procedures

  • Surgery is carried out under general anesthesia (See Anesthesia). It is performed in a warmed operating room with extensive monitoring
  • Omphalocele
    1. Small defects
    • The hernia sac is separated from the sac contents
    • Bowel contents are returned to the abdominal cavity after being inspected for other abnormalities
    • The base of the hernia sac is ligated (tied off) and excess sac removed
    • The tissues of the abdominal wall are closed with sutures including the skin
    1. A larger defect with a large amount of bowel out of the abdomen is more complicated because the abdominal cavity is relatively small and unable to accommodate the herniated viscera (abdominal contents). Repair is as follows:
    • The hernia sac is separated from the sac contents and a search is made for other anomalies
    • The small abdominal cavity is bluntly stretched by the surgeon and a temporary Dacron-reinforced silo is sutured (Figures 5,6,7) to the edge of the abdominal wall defect to house the bowel that cannot be returned to the abdominal cavity. The silo is gently shortened by squeezing from the outside until the abdominal cavity will accommodate the viscera. This takes several days
    • The child is returned to the operating room to remove the silo and close the defect using abdominal wall tissues or, if necessary, through use of a synthetic material to close the abdominal wall (Figure 8)
  • Gastroschisis
    1. In the majority of cases, the bowel lying outside the abdomen and not covered with peritoneum is debrided (cleaned up) because of the chemical peritonitis (debriding may be very difficult and bowel resection may be necessary).
    • The remaining abdominal contents are inspected for other abnormalities
    • The abdominal cavity is stretched to allow the herniated bowel to be returned to the abdominal cavity without undue pressure. The abdominal wall is then closed
    1. If the abdominal cavity cannot be stretched to accommodate the bowel, an additional procedure is necessary:
    • A temporary Dacron-reinforced Silastic silo (Figure 5,6,7) is sutured to the edge of the abdominal wall defect to house the bowel that cannot be returned to the abdominal cavity
    • The silo is gently shortened by squeezing until the abdominal cavity accommodates the viscera. This takes several days
    • The child is returned to the operating room to remove the silo and close the defect using abdominal wall tissues or, if necessary, through use of a synthetic material to close the abdominal wall (Figure 8)
Figure 5,6,7 - Dacron-reinforced silastic silo is sutured to the to the edge of the abdominal wall defect to house the bowel that cannot be returned to the abdominal cavity. The silo is gently shortened by squeezing from the outside until the abdominal cavity will accommodate the bowel. © J. Norah
Figure 8 - After the bowel is returned, the abdominal wall defect is closed. © J. Norah

Complications:

  • Bleeding
  • Respiratory distress
  • Hypothermia (low body temperature)
  • Low urine output
  • Infection
  • Bowel obstruction

Care After Surgery

  • The child is cared for in an intensive care unit to ensure adequate breathing. The child may require ventilator support
  • Temperature and urine output is monitored
  • Fluids are initially given by vein until the surgeon is sure the bowel is functioning
  • A tube is placed through the nose into the stomach to keep the stomach decompressed
  • Antibiotics are usually given
  • Prolonged intensive care may be required

After Care

  • The children may be hospitalized for long periods and require special follow up
  • The goal is to have a healthy baby that is able to eat, urinate, and eliminate stool at the time of discharge without need for respiratory or special nutritional support
  • Follow up is determined by the complexity of the omphalocele or gastroschisis