Congenital Diaphragmatic Hernia and Eventration of the Diaphragm

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CHAPTER 10 Congenital Diaphragmatic Hernia and Eventration of the Diaphragm

Jason S. Frischer, Keith A. Kuenzler, Charles J.H. Stolar

Congenital Diaphragmatic Hernia

Step 1: Surgical Anatomy

♦ Congenital diaphragmatic hernia (CDH) typically refers to a defect in the posterolateral diaphragm, known as the foramen of Bochdalek. The abdominal viscera translocate through this defect into the chest during fetal development.
♦ The diaphragm is a musculotendinous dome-shaped construction that separates the thoracic and peritoneal cavities. The central tendon is a fibrous structure that accounts for about one third of the total surface area of the diaphragm and is the insertion point for the crural fibers that pass around the aorta and the esophagus and continue to the ligament of Treitz.
♦ The diaphragm develops during weeks 4 through 8 of gestation from several fused embryonic components, including the septum transversum, pleuroperitoneal membranes or folds, and the mesentery of the esophagus. The septum transversum forms the central tendon. Closure of the pleuroperitoneal membranes completes the formation of the fetal diaphragm. It is hypothesized that the posterolateral defect in the diaphragm is a result of incomplete or absent fusion of these membranes. As a consequence, the abdominal viscera migrate into the chest during the first trimester.
♦ The ipsilateral lung is affected more than the contralateral lung, but both are affected. The microstructural abnormality features compromised pulmonary arterial divisions, muscular hypertrophy of the intra-acinar arterioles, decreased bronchiolar units, and consequently a decreased surface available for gas exchange. Affected infants are born with both pulmonary hypoplasia and pulmonary hypertension. The pulmonary hypoplasia can be severe enough to preclude survival without fetal circulation, but successful management of the pulmonary hypertension can enable to infant to thrive.
♦ Incidence of CDH varies from 1 in 2200 to 1 in 5000 births. Most series report that around 80% of cases occur on the left side and 20% will contain a hernia sac.

Step 2: Preoperative Considerations

Diagnosis

♦ The diagnosis is typically made antenatally. The infant is usually full term and manifests respiratory distress immediately.
♦ Prenatal ultrasound demonstrates a fetus with bowel, liver, or spleen in the chest and shifting of the mediastinum.
♦ At birth the diagnosis is confirmed by chest radiograph showing loops of bowel in the thoracic cavity with contralateral mediastinal shift.
♦ The chest is usually barrel-shaped, and the abdomen is scaphoid.

Resuscitation

♦ Prompt intubation and nasogastric decompression should be the first steps in the resuscitation process.
♦ Ventilator strategies depend on the clinical situation.

image Patients should always be allowed to breathe spontaneously, and paralytic agents should be avoided to minimize barotrauma.
image Ventilator settings range from low rates with modest peak airway pressures to high-rate ventilation with negligible peak pressures. High-frequency oscillating ventilation is an excellent strategy as well.

♦ Standard monitoring should be immediately instituted with the addition of preductal and postductal arterial oxygen saturation (Sao2).

image Most of these infants have significant pulmonary hypertension leading to right-to-left shunting at the patent ductus arteriosus, and therefore blood gas monitoring via the umbilical artery (postductal) is often misleading.
image Preductal partial pressure of arterial oxygen (Pao2) and the partial pressure of carbon dioxide (Pco2) are more accurate predictors of the lungs’ ability to provide meaningful gas exchange.

♦ Arterial and venous accesses are required to assist in the resuscitation of the infant in respiratory distress.
♦ An echocardiogram is obtained with special attention to signs of pulmonary hypertension. Pharmacologic supports that either dilate the pulmonary vasculature or assist in improving right-sided heart function are useful. Agents such as nitric oxide, iloprost, epoprostenol, sildenafil, dobutamine, and milrinone have all been used to help improve the pulmonary hypertension or its effects.
♦ Extracorporeal membrane oxygenation (ECMO, discussed in Chapter 2) is an adjunct in the preoperative infant who has already demonstrated evidence of adequate lung function but who then deteriorates secondary to pulmonary hypertension. The likelihood that this infant would tolerate surgery is low, and therefore the added cardiopulmonary support will allow the infant to recover from the acute pulmonary hypertensive crisis. Repair is typically performed when ECMO parameters are near the time of decannulation. The infant is usually weaned off ECMO support within 1 to 2 days after closure of the diaphragmatic defect.

Step 3: Operative Steps

Anesthesia

♦ An orotracheal or nasotracheal tube is used to secure the airway. A nasotracheal tube has the theoretical advantage of lower incidence of airway complications, but an orotracheal tube is easier to place and more commonly used.
♦ A pressure-cycled infant ventilator is preferred over the conventional anesthesia circuit to provide mechanical ventilation to the infant.
♦ Muscle paralysis and narcotics are administered and complemented with intravenous anesthetic agents on an as-needed basis.
♦ Continuous oxygen saturation monitoring, both preductal and postductal, is critical, as are blood gas observations of hypercapnia and ventilator adjustments as needed.

Positioning

♦ The operative room should be warmed, and focus should include keeping the patient warm at all times. Plastic drapes are used to cover the child outside the operating field.
♦ The infant is placed in the supine position on a heating apparatus.
♦ A small roll is used to elevate the ipsilateral subcostal region.

Incision

♦ A subcostal incision is made on the side of the hernia.
♦ The incision is made approximately one fingerbreadth below the costal margin. While incising the anterior abdominal wall musculature and fascia, be careful to leave enough fascia and muscle on the cephalad aspect of the wound to provide for an adequate closure (Fig. 10-1).
♦ Electrocautery is used to ensure hemostasis because of the potential need for ECMO and anticoagulation.
image

Figure 10-1

Hernia Reduction

♦ The upper portion of the wound is retracted in a cephalad direction along with the upper rim of diaphragm. The entire defect should be exposed. Carefully reduce the abdominal contents back into the abdominal cavity, or eviscerate the contents during the repair.
♦ The bowel should be placed in the abdominal cavity in an organized fashion, focusing attention on the orientation of the mesentery.
♦ Reduction of the liver deserves vigilance because of the extremely fragile nature of the neonatal liver. Similar caution should be made when reducing the spleen and care taken with its attachments to the pancreas and colon.

Repair of the Diaphragm

♦ Identify the anterior rim of the diaphragm and trace it medially to free up the mesothelial covering. The diaphragmatic edge should be completely mobilized.
♦ Primary repair is accomplished by using interrupted simple sutures with nonabsorbable material (Fig. 10-2).
♦ If the repair is too large for primary repair, a prosthetic patch can be created using 1-mm-thick Gore-Tex. The patch should be sized carefully and secured with monofilament interrupted sutures (Fig. 10-3).
image

Figure 10-2

image

Figure 10-3

Closing

♦ The abdomen is closed in layers.
♦ The loss of abdominal domain can potentially make wound closure challenging. One should not be reticent about placing either a patch or a silo to close the abdomen.
♦ A chest tube is usually not necessary after repair of CDH.

image Infants repaired on ECMO, where anticoagulation is required, and those with a pneumothorax or unexpected bleeding are the only patients who require an ipsilateral tube thoracostomy.

Step 4: Postoperative Care

♦ The preoperative care strategy is reinstituted in the postoperative period.
♦ Spontaneous respiration and permissive hypercapnia are the mainstays of the respiratory strategy.
♦ Narcotics are necessary to ensure adequate analgesia.
♦ Similar to other laparotomies, sufficient circulating volume must be maintained with intravenous fluids, and adequate hemoglobin must be maintained for oxygen delivery.
♦ Mechanical ventilation should be converted to nasal-prong continuous positive airway pressure assisted ventilation when the infant stabilizes and subsequently weaned as tolerated.
♦ Parenteral nutrition is provided until respiratory status improves, the neonate has return of bowel function, and the infant is weaned to full enteral feeds.

Step 5: Pearls and Pitfalls

♦ When making a subcostal incision, be sure to leave sufficient tissue on the cephalad portion of the wound to allow for adequate closure.
♦ With using a patch for large defects, the ribs can be used for anchoring the lateral aspect. On the medial side, if there is a paucity of tissue, one must be creative and anchor to structures around the hiatus or pericardium.
♦ Postoperative volvulus is a rare complication, and therefore correction of the nonrotated bowel is unnecessary. Division of Ladd’s bands, with or without appendectomy, is discouraged because of the increased incidence of bleeding if the patient needs to go on ECMO.

Thoracoscopic CDH Repair

Step 1: Surgical Anatomy

See page 85 for a description of the anatomy.

Step 2: Preoperative Considerations

♦ As with other diseases, early efforts to apply minimally invasive techniques to CDH began with older children. As advances in optics and instrumentation have been made, it has been possible to perform successful neonatal repairs. Although no clear advantage has been demonstrated yet, we consider a thoracoscopic approach for all newborns with CDH who are hemodynamically stable and able to tolerate the low-pressure pneumothorax required.
♦ Specifically, these patients are newborns on conventional ventilator, requiring low supplemental oxygen and pressure support settings.
♦ As our experience has increased, we have successfully repaired CDH defects on the left and right sides, both primarily and with synthetic patch material.
♦ Monitoring and support lines are identical to those described for the open repair.

Step 3: Operative Steps

Positioning

♦ The infant is placed in the lateral decubitus position.
♦ An axillary roll is placed, and bony prominences are padded.
♦ Elevating the infant off the operating table on narrow stack of pads or towels will allow the thoracoscopic instruments a greater range of motion.
♦ The surgeon stands at the infant’s head with the video screen positioned over the legs in direct line of vision.

Trocar Placement

♦ Three 5-mm radially expandable sleeves and trocars are used.
♦ The first port is placed in the posterior axillary line caudal to the level of the scapula.
♦ A 4-mm, 30-degree scope is used.
♦ The pneumothorax is slowly increased to 5 mm Hg while monitoring for ventilatory changes.
♦ The two working ports are then inserted under thoracoscopic visualization. These are placed several centimeters to either side of the first port, one to two rib spaces caudally.

Reduction of Viscera and Repair of Defect

♦ The viscera are gently reduced into the abdomen using cotton-tipped “endo-peanut” instruments.
♦ Insufflation assists not only in the reduction but also in the maintenance of operative space by keeping the viscera from returning to the thorax.
♦ A hernia sac, if found, is completely excised so that the diaphragmatic edges can be properly identified and apposed.
♦ Primary repair is done from the medial to lateral aspects using 2-0 braided nonabsorbable sutures on standard taper needles. We prefer to place these sutures in simple fashion. Alternatively, one may elect to use “U” stitches with or without pledgets.
♦ Identical to the open repair, a synthetic patch may be placed into a large defect or as an “onlay” over a weaker area. The patch material is cut to proper size and then rolled tightly so that it will pass through the 5-mm port (mineral oil or other lubrication may facilitate its passage).

Optional Pericostal Sutures

♦ Completion of a primary or patch repair may require pericostal sutures.
♦ Once the rib is identified, a tiny adjacent skin incision is made using a #11 blade.
♦ The suture is then passed through this incision through the intercostal space and into the thorax on a “ski” needle.
♦ The suture is retrieved and passed with the thoracoscopic needle driver through the diaphragm or patch and then driven back out of the chest on the other side of the rib.
♦ Sutures are tied extracorporeally with the knots buried subcutaneously beneath the tiny skin incisions, which are subsequently closed with Steri-strips.

Step 4: Postoperative Care

See page 90 for a description of the postoperative care.

Step 5: Pearls and Pitfalls

♦ Both intracorporeal and extracorporeal knot tying may be useful.
♦ Similar to the open technique, placement of sutures around the ribs can be used to anchor a patch in the lateral aspect. These sutures may be placed through a separate small incision made directly over the identified ribs.

Eventration of the Diaphragm

Step 1: Surgical Anatomy

♦ Eventration of the diaphragm refers to a radiographic finding of an abnormally elevated hemidiaphragm that can either be congenital or acquired.
♦ Congenital eventrations can either be due to birth trauma, Erb’s palsy, or secondary to an anatomic abnormality of the diaphragm, in which case the muscle is typically thinned or may be absent.
♦ Acquired eventrations are usually secondary to phrenic nerve injury during repair of congenital cardiac defects. These lesions, like those of birth trauma or Erb’s palsy, are associated with normal diaphragm musculature.

Step 2: Preoperative Considerations

Diagnosis

♦ Initial workup includes a chest radiograph preferably with an anteroposterior and lateral view, which is imperative.

image A right-sided eventration is suspected when the ipsilateral hemidiaphragm is greater than two rib levels higher than the left.
image A left sided eventration is entertained when the left hemidiaphragm is one rib level above the right diaphragm.
image The diagnosis is confirmed by dynamic visualization of the diaphragm using either fluoroscopy or ultrasonography of the chest and observing the movement of the diaphragm.
image Absent or paradoxical elevation of the diaphragm on inspiration is diagnostic of eventration.

Associated Anomalies

♦ Structural cardiac anomalies are associated with patients who have congenital eventration of the diaphragm; therefore an echocardiogram should be obtained.
♦ Intestinal rotational anomalies and gastric volvulus have been reported in patients with diaphragmatic eventration; if symptoms warrant, an upper gastrointestinal contrast study would be prudent.

Indications for Repair

♦ Recurrent symptoms and respiratory distress are absolute indications for repair.
♦ Diaphragm level above the fourth intercostal space or inability to wean from the ventilator would be an indication.
♦ When phrenic nerve injury is suspected, a waiting period before instituting operative therapy is reasonable.

Step 3: Operative Steps

Anesthesia

♦ The anesthetic approach is standard for any infant. Intravenous and inhaled agents may be used.
♦ Although not mandatory, establishing single-lung ventilation on the contralateral side would assist in making the eventration repair easier. This is especially true for the thoracic approach.

Positioning

♦ Positioning depends on the approach.

image A lateral decubitus position is used for a thoracic approach.
image Supine positioning is appropriate for an abdominal approach.

Incision

♦ A lateral muscle-sparing thoracotomy is made in the seventh intercostal space for an isolated unilateral eventration.
♦ A transverse upper abdominal incision is used for an eventration associated with malrotation or for the rare instance of a bilateral eventration.

Repair of the Eventration

♦ Open techniques as well as minimally invasive techniques through the abdominal and thoracic approach may be used to repair an eventration.
♦ The first step is to grasp the diaphragm and manipulate the muscle to determine the amount necessary to create a taut repair (Fig. 10-4).
♦ Non-absorbable suture is used to plicate the muscle with several full-thickness bites in order to craft a pleating of the diaphragm (Fig. 10-5).
♦ A chest tube is usually not necessary after repair of diaphragmatic eventrations.
image

Figure 10-4

image

Figure 10-5

Step 4: Postoperative Care

♦ Postoperative care is similar to that of congenital diaphragmatic hernia repair but is generally simpler because of the absence of pulmonary hypertension.

Step 5: Pearls and Pitfalls

♦ Thoracoscopic approach can be used by experienced endoscopic surgeons.
♦ A taut repair is vital to minimize recurrent symptoms.

Bibliography

Boloker J, Bateman DA, Wung JT, et al. Congenital diaphragmatic hernia in 120 infants treated consecutively with permissive hypercapnia/spontaneous respiration/elective repair. J Pediatr Surg. 2002;37:357-366.

Hines MH. Video-assisted diaphragm plication in children. Ann Thorac Surg. 2003;76:234-236.

Lally KP, Harting MT. Surgical management of neonates with congenital diaphragmatic hernia. Semin Pediatr Surg. 2007;16:109-114.

Lally KP, Lally PA, Van Meurs KP, et al. Treatment evolution in high-risk congenital diaphragmatic hernia: ten years’ experience with diaphragmatic agenesis. Ann Surg. 2006;244:505-513.

Stolar CJH, Dillon PW. Congenital Diaphragmatic Hernia and Eventration. In: Grosfeld JL, O’Neill JAJr, Fonkalsrud EW, Coran AG, editors. Pediatric Surgery. 6th ed. Philadelphia: Mosby Elsevier; 2006:931-954.

West SD, Wilson JM. Follow up of infants with congenital diaphragmatic hernia. Semin Perinatol. 2005;29:129-133.

Yang EY, Allmendinger N, Johnson SM, et al. Neonatal thoracoscopic repair of congenital diaphragmatic hernia: selection criteria for successful outcome. J Pediatr Surg. 2005;40:1369-1375.

Yazici M, Karaca I, Arikan A, et al. Congenital eventration of the diaphragm in children: 25 years’ experience in three pediatric surgery centers. Eur J Pediatr Surg. 2003;13:298-301.

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