Pediatric Omphalocele and Gastroschisis Treatment & Management

Intestinal inflammation

• Intestinal inflammation may occur with either gastroschisis or rupture of an omphalocele.
• The eviscerated intestine may appear entirely normal, as if a surgeon had made a fresh laparotomy incision, or may be grossly abnormal in appearance with shortened length and surface exudate. Function follows appearance; these babies may tolerate feedings immediately or may require prolonged parenteral nutrition because of intestinal dysmotility and malabsorption. The extent of intestinal dysfunction depends on the magnitude of the inflammatory and ischemic injury caused by exposure to the amniotic fluid and compression of the herniated intestinal mesentery by the abdominal wall defect.
• The inflamed intestine is thick and edematous, the loops of bowel are matted together, and the mesentery is congested and shortened.
• Histology reveals atrophy of the myenteric ganglion cells.
• The inflamed intestine is dysmotile, with prolonged transit time and decreased absorption of carbohydrate, fat, and protein. These deleterious effects remit as the inflammation resolves, usually in 4-6 weeks. During this time, total parenteral nutrition (TPN) is required.

Intact omphalocele

• Neonates with intact omphaloceles are usually in no distress unless associated pulmonary hypoplasia is present.
• The baby should be carefully examined to detect any associated problems, such as Beckwith-Wiedemann syndrome, chromosomal abnormalities, congenital heart disease, or any other associated malformations.
• Maintenance intravenous (IV) fluids are administered, and the omphalocele sac is covered with a nonadherent dressing, such as Xeroform, wrapped with Kerlix, and then covered with Saran wrap to preserve body heat and moisture.
• Prophylactic antibiotics may be given preoperatively if an associated intestinal anomaly is suspected.
• Closure of a small or moderate-sized omphalocele is accomplished without difficulty.
• A baby with a ruptured omphalocele is treated the same way as a baby with gastroschisis.^[18]
• Closure of giant omphaloceles containing the liver is always challenging.^{[26, 27, 28]}

Gastroschisis

• Respiratory distress in a neonate with gastroschisis may respond to gastric decompression, although endotracheal intubation may still be needed.
• Fluid, electrolyte, and heat losses must be minimized and corrected. Because of significant ongoing fluid losses with an open abdominal wall defect, administer an IV fluid bolus (20 mL/kg lactated ringer solution or normal saline), followed by 10% dextrose/0.25 normal sodium chloride solution at 2-3 times the baby's maintenance fluid rate. This will also help compensate for postoperative third space loses.
• The baby should be placed under a radiant heater. The exposed intestines may be covered with a moist laparotomy pad; and the eviscerated intestine should be situated on top of the baby's abdomen and wrapped with Kerlix in a way that avoids applying traction upon the bowel mesentery.
• A urinary catheter should be inserted to monitor urine output and asses the efficacy of fluid resuscitation. A rectal examination should be performed to dilate the anal canal. Reduction of the herniated viscera is facilitated by evacuating meconium from the sigmoid colon; this can be easily accomplished during the operative procedure.
• Broad-spectrum antibiotics are administered to prevent contamination of the peritoneal cavity.
• A central venous line is placed intraoperatively to provide parenteral nutrition, thereby minimizing catabolic protein loss during the period of GI dysfunction.^{[21, 7, 22]}

Omphalocele

Ambroise Pare, a 17th-century French surgeon, accurately described the dire consequences of opening the omphalocele sac to obtain closure of the abdominal wall. His experience encouraged conservative treatment such as squeezing the sac to reduce the herniated viscera or painting the sac with escharotic agents to promote contraction and epithelization. This approach prolongs healing; during this time, the sac may rupture and a wound infection may result. Even if complications do not occur, the healing of such a large wound exacts a significant metabolic and nutritional toll.

Healing may be hastened by mobilizing skin flaps to cover the omphalocele sac (Gross technique); however, this results in the creation of a large ventral hernia.

In 1967, Schuster developed a technique that more expeditiously treats babies with giant omphaloceles. It may also be used to correct ventral hernias created by skin flap closure.

A circumferential incision is made along the skin-omphalocele junction; the omphalocele membrane is left intact. The incision is extended in the midline and the rectus fascia is exposed from xiphoid to pubis. Teflon sheets are sutured along the edge of the fascia and approximated over the omphalocele sac.

Reduction is effected by gradually pulling the Teflon sheets and attached rectus muscles over the liver and suturing them in the midline. At an appropriate time, the Teflon sheets are removed, the omphalocele sac is excised, and a DualMesh patch (Gore-Tex) is sutured circumferentially to the remaining fascial defect.

The patch is made larger than the abdominal wall defect giving the anterior abdominal wall a concave appearance and lessening pressure on the diaphragm. Skin flaps are laterally mobilized and approximated over the patch.

The patch is attached to the margins of the abdominal wall defect, superiorly to the costal arch, inferiorly to the pubis, and laterally to the rectus fascia. Growth of the abdominal wall is stimulated by the increased intra-abdominal pressure, elevating the costal arch, and expanding the thoracic cavity.

A Gore-Tex patch requires skin coverage, whereas an AlloDerm patch (acellular human dermis) does not because it is vascularized by the underlying liver. It may be left exposed and dressed with a topical antimicrobial, such as mupirocin ointment. Like a partial thickness burn wound, it is epithelialized. This is advantageous for wound healing; because it is vascularized, the patch is no longer a foreign body that may become infected and require removal. However, a disadvantage of AlloDerm is that it is not rigid, and a ventral hernia develops that ultimately requires repair with a rigid patch (see the images below).^{[29, 30]}

Gastroschisis

In 1969, Allen and Wrenn adapted Schuster's technique to treat gastroschisis.

Silastic sheets are sutured to the full thickness of the extended abdominal wall defect and closed over the eviscerated intestine, whose reduction is facilitated by stretching the abdominal musculature, emptying the stomach and bladder, and manually evacuating the colon.

The major factor permitting reduction of the extruded viscera is resolution of the intestinal inflammation; in time the rigid, congealed mass is transformed into multiple soft, pliable loops of intestine, which can fit into the nooks and crannies of the abdominal cavity.^{[31, 32]}

Too tight a closure of the abdominal wall must be avoided, for this limits excursion of the diaphragm and necessitates increased inspiratory pressure to compensate for the increase in ventilatory resistance. In general, peak inspiratory pressures (PIPs) higher than 25 mm Hg should be avoided. High-frequency oscillatory ventilation may be an alternative to conventional ventilation if intra-abdominal pressures are markedly increased.^[33]

In addition, tight closure of the abdominal cavity impedes venous return to the heart, which compromises cardiac output and decreases renal blood flow and glomerular filtration rate. Renal vein thrombosis and renal failure may ensue. Diminished mesenteric blood flow compounds the risk of necrotizing enterocolitis (NEC) because the intestine of these infants is immature immunologically and the dysmotility leads to stagnation and bacterial overgrowth.^[34]

The intra-abdominal pressure can be measured by connecting a manometer to a Foley catheter or a nasogastric tube. The central venous pressure, intravesical pressure, and the intragastric pressure should not exceed 20 cm H₂ O to avoid development of the abdominal compartment syndrome.^[13]

The alternative ways of managing babies with abdominal wall defects generates lively discussion among colleagues. This generally indicates that disparate techniques yield equivalent results; because no one technique is demonstrably superior, personal preference is determinative.

The main dilemma is balancing the safety of the reduction of the viscera and closure of the defect against the risk of complications. The safety of reduction and closure techniques is related to the level of intra-abdominal pressure and, therefore, the degree of viscera-abdominal disproportion. This, in turn, influences the risk of complications and outcome. Minimizing intra-abdominal hypertension (IAH) and avoiding abdominal compartment syndrome is important.

An intra-abdominal pressure of more than 15 mm Hg influences IAH and more than 20 mm Hg influences abdominal compartment syndrome. The effects of IAH are both hemodynamic and ventilatory. Reduced cardiac output and reduced splanchnic perfusion pressure lead to oliguria and gut mucosal acidosis; hypoventilation compounds the hemodynamic effects. In turn, this leads to abdominal compartment syndrome and potentially devastating physiological complications, including renal failure, sepsis, bowel ischemia, and wound complications.

Bowel ischemia may develop into NEC, which may lead to loss of bowel, resulting in short bowel syndrome. Wound complications include dehiscence, sepsis, and enterocutaneous fistula and can lead to negative cosmetic outcomes. Tight closure of gastroschisis may be involved in as many as 75% of patients who have short bowel syndrome who are referred for transplantation.^[35]

Questions include the following:

• Should these babies be delivered by cesarean delivery or vaginally?
• Should a prefabricated silo be placed in the NICU with sedation or in the OR under general anesthesia? Does this matter?
• Can the intestines be more thoroughly cleansed and the anatomy assessed in the OR rather than in the NICU?
• Are "off the shelf" silos preferable to those fabricated by the surgeon from silon sheets?
• Does stretching the flaccid (paralyzed) abdominal wall enlarge the abdominal cavity?
• Is enterolysis of the inflamed intestine, cutting through the inflammatory peel and separating the congealed loops of intestine feasible, or is the risk of damaging the intestine prohibitive?
• Should an attempt be made to evacuate meconium from the intestine?
• Does squeezing the intestine injure the serosa and promote formation of adhesions?
• Should the appendix be removed, and the opening in the cecum used to evacuate the meconium?
• Should the surgeon dilate the anus and milk the meconium through the colon into the rectum and out the anal canal?
• If a silo is placed, should pressure be applied to the eviscerated intestine, and does this pressure cause enlargement of the abdominal cavity?
• Is resolution of inflammation the determinative factor effecting reduction? In which case, simply allowing the intestine to sink by gravity into the abdominal cavity should be sufficient.
• When should a silo be removed to minimize the risk of infection?
• Which antibiotics should be used?
• Should the antibiotic cover gut or skin flora?

According to recent guidelines,^{[35, 36]} success with primary reduction at the cot side, also known as ward reduction (WR), may be the best technique in some situations. Selection and conversion criteria that preclude WR include poor bowel condition, bowel/mesentery attached to the defect, gross viscera-abdominal disproportion, narrow defect diameter, and deteriorating metabolic acidosis.^[35]

The use of a preformed silo is an efficacious treatment modality. However, precautions are noted.^[36] Reduction of gastroschisis against a tight silo ring may result in venous congestion. This may directly cause bowel ischemia and necrosis. For patients with gastroschisis treated with a preformed silo, close inspection of the reduction process is recommended. Specifically, verify that the bowel at the base of the silo is actually reducing into the abdomen with manual reduction of the silo. Otherwise, it may simply be compressing the bowel against the loops at the bottom of the silo or against a tight ring of the silo or fascial defect, causing congestion and possible ischemia. For any signs of venous congestion, the recommendation is immediate removal of the silo and inspection of the intestines.^[36]

See the image below.

The baby in the image above has high jejuna atresia and necrosis of the distal small intestine. The gray area (in the center of the photograph) is necrosis of the antimesenteric aspect of the proximal jejunum. This was excised and the remaining plaque was tubularized. The bulbous end of the small intestine was preserved. The gray area (on the right in the photograph) is necrotic (distal) small intestine. The extruded intestine was dissected despite the inflammatory peel and reduction effected without creating an ostomy. The intestinal obstruction was not relieved, so that the tubularized segment would dilate. Later, a STEP procedure^[37] was performed on the bulbous distal jejunum, and this end was joined to the proximal "microcolon." This anastomosis strictured and was revised twice.

An additional enterolysis was necessary before intestinal function was established. Ultimately the baby was transferred, and 2 more STEP procedures were performed; however, intestinal transplantation was not deemed necessary.

See the images below.

Neonatologists and pediatric surgeons share the responsibility for the treatment of these babies.

Consultation with a cardiologist, pulmonologist, gastroenterologist, and geneticist may be indicated.

Babies with omphaloceles have normal intestine and do not require special formulas. The occasional intestinal atresia, perhaps associated with a patent omphalomesenteric duct, is not usually associated with short gut.

Babies with gastroschisis, on the other hand, may have sustained injury to the intestine and require elemental or protein hydrolysate formulas, lactose-free carbohydrates, and medium-chain triglycerides.

Babies with short-gut syndrome absorb medium-chain triglycerides more readily than long-chain triglycerides; however, the latter are more valuable as regards gut adaptation.

The liver of a child with a repaired giant omphalocele is located in the epigastrium, where it is more vulnerable to trauma; therefore, contact sports should be avoided.