153: Long-Term Outcomes After a Congenital Diaphragmatic Hernia Repair: Implications for Adult Thoracic Surgeons

Survival of infants born with congenital diaphragmatic hernias (CDHs), as with many other anomalies in pediatrics, has steadily improved over the last three decades owing to advances in critical care medicine, as well as surgical technique. While early attempts to repair CDH were made in emergent fashion, recognition that the life-threatening issue was not mechanical compression of the lungs or mediastinal structures, but disordered pulmonary vascular reactivity, has been the major advance in improving survival and outcomes. There is wide variation in the technical approach to the repair of these anomalies including variability in pre- and postoperative care, timing of the operation, abdominal or thoracic operative approach, and choice of prosthetic material for closure. The intent of this chapter is to provide the adult thoracic surgeon with a reference for review of the current management of CDH and discuss the impact of having these diaphragmatic defects repaired as an infant or child on general thoracic anomalies/procedures in the adult.

The most common type of CDH is the Bochdalek hernia (Fig. 153-1). These occur posterolaterally and most commonly on the left. In general, Bochdalek hernias are categorized on the basis of size. Small defects are usually triangular in shape, with the apex medially and the base on the chest wall. Small defects most often are repaired primarily. Medium-sized defects have a larger segment of missing diaphragm, often leading to inability to close by primary repair. These defects may require a prosthetic patch, which usually includes sutures placed around the ribs laterally. The largest defects are commonly referred to as agenesis of the hemidiaphragm, and require nearly complete replacement of the hemidiaphragm with prosthetic patch material. The medium and large defects tend to have vanishingly small amounts of tissue along the esophagus and aorta to which the patch can be sewn. Consequently, gastroesophageal reflux (GERD) is more common in the medium and large defect forms of CDH leading these patients to be more likely to require a fundoplication to control their reflux. Another reason that patients with a patch repair have more reflux is that the patch does not grow as the patient does, and may, therefore, pull on the esophageal hiatus as the patient grows.

Morgagni hernias are located in the midline just posterior to the sternum. These defects can have little to no symptoms. Consequently, Morgagni hernias are most commonly diagnosed with older patients who have chest x-rays for other reasons and a mediastinal mass is seen. These Morgagni defects are commonly closed primarily; however, on rare occasion, a patch may be required. Morgagni defects are also seen in pentalogy of Cantrell, and in that case, are usually bilateral.

Eventration of the diaphragm (Fig. 153-2) occurs in the congenitally thin muscular portion of the hemidiaphragm. It occurs far more frequently on the right (5:1), as the heart tends to be protective. The eventration occurs anteromedially. It is often mistaken for CDH with an associated membrane sac; however, clinically and anatomically, eventration is a different entity (Fig. 153-3). As depicted in Figure 153-2, anatomically, there is still a small rim of diaphragmatic tissue. Diagnosis of eventration is elucidated either by a fluoroscopic diaphragmatic excursion study or by ultrasound, where paradoxical movement of the diaphragm is seen. Treatment consists of halting this paradoxical movement of the diaphragm though plication of the tissue. Surgical intervention is warranted when there is an inability to wean from a ventilator or when the respiratory status causes failure to thrive—often due to caloric consumption from tachypnea.

The majority of Bochdalek CDHs are identified antenatally by routine ultrasound screening. Consequently, these children are delivered with the planning and presence of a pediatric surgeon, and critical care resources are ready for the immediate resuscitation and care of the baby starting in the delivery room. After delivery, the baby is intubated and a nasogastric tube is placed to decompress the stomach, which is commonly located in the chest (Fig. 153-4). Gastric decompression reduces gastric distention by fluid or gas introduced by the initial resuscitation, which can exacerbate the hemodynamic effects of pulmonary mechanical compression by the abdominal contents. Extracorporeal membrane oxygenation (ECMO) is used for the rescue of babies whose pulmonary hypertension is so severe that gas exchange cannot be adequately achieved using either conventional or oscillatory ventilation. Inhaled nitric oxide is commonly employed to facilitate pulmonary capillary dilation with subsequent improved oxygenation and normalization of serum pH.

If conventional ventilation with or without nitric oxide were adequate for the support of the infant, then operation is delayed until hemodynamic stability is achieved. If ECMO is used, then repair can be performed while on ECMO. Morgagni hernias are repaired electively.

The most common technical approach to repair of CDH is by laparotomy. A subcostal incision is made on the side of the defect, and the size of the defect is assessed to determine if a primary closure can be achieved with acceptably minimal tension. A posteromedial rim is identified and dissected from the retroperitoneum. A primary repair is performed when the diaphragmatic defect is small (Fig. 153-5). This repair is usually performed with interrupted sutures of non-absorbable material; however, some surgeons will use long-lasting absorbable sutures such as PDS.

When the diaphragmatic defect is large, a prosthetic patch must be used to close the defect, reduce the compression of the lungs and mediastinal structures, and hold the abdominal contents below the diaphragm. In a patch repair, the most challenging technical task is the creation of a substantial medial rim of tissue along the aorta and esophagus. This rim must be capable of holding suture for either primary closure or prosthetic material. The mechanically weak nature of this tissue leads to an increased risk of hiatal hernia and reflux issues in these babies as they grow. Additionally, sutures may be (unintentionally) placed in the periadventitial tissue on the left lateral edge of the aorta, since in many cases the tissue is essentially nonexistent in this region. The adult general thoracic surgeon should take great care when reoperating in this region, particularly when patch material has been used. Adhesions formed in this area in conjunction with sutures that may have been placed in the adventitia of the aorta, and this leads to substantial risk of aortic injury when reoperations are performed.

Whatever material is used for the repair, the patch is made sufficiently large to avoid tension due to undersizing. With large defects, the patch is secured to the ribs by passing sutures carefully around the rib. As previously discussed, medial sutures may include tissue located close the aorta because of sparse tissue volume in this area. As the child grows, this small patch becomes encapsulated and, if fixed to the ribs, may remain so fixed. Depending on the material used, adhesions will form on both the abdominal and thoracic sides of the diaphragm. While some surgeons use a single patch material such as PTFE, others creates a “sandwich” using one patch material on the thoracic side and a different patch material on the abdominal side in an effort to reduce the chance of recurrence. Consequently, it is certainly beneficial to obtain an operative note that describes the patch construction prior to reoperating. When the defect is too large for primary repair, some surgeons create a split abdominal wall muscle flap by separating the transversalis and internal oblique muscles, and turn the flap upward to patch the diaphragmatic hernia defect.

In the last several years, minimally invasive techniques have been used to repair both Morgagni and Bochdalek hernias. Morgagni hernias usually can be closed primarily often via a laparoscopic approach, although, in rare cases, a patch may be used. Minimally invasive repair of diaphragmatic hernia usually is approached through the chest. Primary repairs are fairly straightforward and have a similar recurrence rate to an open repair. Patch repairs are certainly more technically challenging and these repairs are associated with a modestly higher recurrence rate than when a patch is placed in open fashion.

Recurrence of diaphragmatic hernia can be managed in a minimally invasive fashion (Fig. 153-6). When the recurrence is small, a thoracoscopic approach can allow the placement of interrupted sutures with reduction of the herniated contents. When the recurrence is larger, a full laparotomy may be necessary. Depending on the material used in patch repairs, the spleen, colon, and stomach may be densely adherent to the patch. Dense adhesions also may be present at the gastroesophageal junction making injury to the esophagus or aorta an important concern during operations for recurrent diaphragmatic hernia. Whatever technique is used for CDH repair, surgeons reoperating in the chest or abdomen should be aware that they could encounter recurrence of CDH in the form of breakdown of the primary repair or peri-patch hernia (recurrent hernia).

Since its introduction for CDH in 1977, ECMO has become a useful adjunct in the perioperative management of CDH patients. When acidosis and hypoxic respiratory failure persist despite maximal medical therapy, including low-tidal volume ventilation, nitric oxide, inotropes and vasopressors, ECMO is considered.

Once on ECMO, the CDH-associated predicted mortality is 52%. ECMO cannulation can be venovenous or venoarterial. The adult thoracic surgeon should take care to look for an incision on the right neck indicating possible previous ECMO cannulation as an infant. The right common carotid artery, and the right internal jugular vein are the common sites of inflow and outflow cannula placement, respectively. When patients are decannulated, these vessels are routinely ligated in neonates.

These vessels are commonly accessed through a transverse cervical incision, one fingerbreadth above the clavicle, with dissection between the sternal and clavicular heads of the sternocleidomastoid muscle. Upon decannulation, the vessels are normally tied off, often with permanent sutures to permit the potential for future identification. Recannulation to put a patient back on an ECMO circuit is rare for the repaired diaphragmatic hernia patient. This can still be accomplished through the same vessels, although a partial or, less frequently, complete midline sternotomy may be necessary to recannulate the common carotid and internal jugular vessels.

The role of ECMO in reducing ventilator-associated lung injury does not come without cost. Patients are anticoagulated while on the circuit, which creates the potential for intracerebral/intraventricular hemorrhage, procedure-associated bleeding, and subsequent neurodevelopmental sequelae. Patients on ECMO are more likely to experience nutrition-related issues, including failure to thrive and GERD. ECMO patients are nearly four times more likely to have undergone surgical intervention (fundoplication) for GERD versus non-ECMO counterparts.¹

The diagnosis of CDH is associated with a mortality rate of 40% to 50% depending on the population being studied. CDH patients tend to have multisystem disease processes that must be considered when planning an operation later in life. Up to 50% of CDH patients also have associated additional congenital malformations. These early malformations include intestinal atresias, congenital cardiovascular disease, and chromosomal anomalies. High-risk patients who undergo cardiorespiratory failure and are cannulated for ECMO are also at risk for serious neurologic sequelae related to peri-cannulation hypoxemia, thromboembolus, or intraventricular hemorrhage, all of which can have life-long neurologic implications.

Overall, outcomes of patients with CDH are dependent on both the inherent pathophysiological process of the disease as well as the different treatment options used for their treatment. Complications include but are not limited to the following: (1) nerve palsies; (2) recurrence of CHD; (3) chylothorax; (4) small bowel obstructions; and (5) persistent pulmonary hypertension. Long-term sequelae include issues with the thoracic/chest wall and GERD.

Nerve palsies are common following repair of the CDH. The diagnosis can be made in the usual fashion with a follow-up x-ray. This specifically complicates an already dysplastic residual diaphragm. In general, it is important to continue to monitor pulmonary function tests and remaining residual functional capacity; often it is the use of inappropriate high pressure ventilatory strategies in the hypoplastic lung parenchyma that cause long-term sequelae.

Chylothorax can present in as many as 28% of CDH patients following surgical repair. Risk factors include prosthetic patch use, prenatal diagnosis, and ECMO cannulation.² Long-term sequelae include and are not limited to nutritional deficiencies, immunologic dysfunction, and the potential for further interventions to correct the persistent loss of proteinaceous and often lymphocyte-rich fluid.

CDH patients are likely to undergo further operations during their lifetime after initial hernia repair. Recurrence is not uncommon following repairs of diaphragmatic hernias. Recurrence may follow both open and thoracoscopic repairs (Fig. 153-7A,B). Recurrence may also follow both primary and prosthetic patch repairs. According to Guner et al., the incidence of recurrence in all CDH patients ranges from 2% to 45%, where the highest incidence occurs in patients who undergo open repair with patch material.³ Recurrence likely occurs from the inherent growth of the child, patch stability, and inherent pathophysiology of the diaphragm itself. Up to 50% of patients who receive a patch repair have subsequent recurrence by 3 years of age.⁴ ECMO recipients are more likely than their non-ECMO counterparts to undergo subsequent procedures, including antireflux operations, recurrent diaphragmatic hernia repair, Ladd's procedure, tracheostomy, and chest wall reconstruction.⁵ Occasionally ECMO patients require an umbilical silo to permit the abdominal space to decompress into the silo, and, therefore, reduce pressure on the repair.⁵ These silos can be placed at the time of defect repair, or following closure to relieve abdominal compartment syndrome. Patients with CDH uniformly have intestinal malrotation. Small bowel obstruction occurs in 4% to 20%, attributed to midgut volvulus, incarcerated CDH recurrence, or intestinal adhesions.^4,6 Laparotomy for small bowel obstruction is the second most commonly performed procedure for CDH patients other than repair of hernia recurrence.⁵

Long-term data categorizing outcomes for CDH patients are lacking. CDH patients who require ECMO embody a high-risk patient group. In general, the degree of pulmonary hypoplasia and pulmonary hypertension are the most significant sources of potential morbidity. These patients more commonly have larger defects, which predisposes them to greater risk of recurrence, scoliosis, and chest wall dissymmetry. Up to one-third of CDH patients may exhibit reduced FEV₁ and FVC values compared to otherwise healthy counterparts on pulmonary function testing. CDH patients who are on mechanical ventilation for more than 7 days have significantly lower FEV₁ and VC than patients who were on the ventilator for less time, likely reflecting both their underlying disease severity and effects of ventilator-induced barotrauma.⁷ There are few studies documenting the influence of pulmonary hypertension in CDH survivors later in life. While some patients exhibit normal exercise capacity and gas exchange parameters in adulthood,⁷ studies have shown approximately one half of children survivors demonstrate evidence of right ventricular hypertension on electrocardiogram.⁸

Chest wall deformities related to abnormal breathing patterns and surgical repair create functional and anatomic barriers for potential thoracic surgery. Apart from intrinsic pulmonary hypoplasia and pulmonary hypertension, chest wall deformities further complicate pulmonary mechanics by adding extraparenchymal lung dysfunction. While scoliosis in young children may be ameliorated by bracing, patients with underlying pulmonary dysfunction often are not suitable candidates for this therapy given the restriction it imposes on chest wall expansion. Studies suggest that lung diffusion capacity, as well as the ability to achieve normal aerobic capacity, is comparable between CDH patients and otherwise healthy controls.⁵ The combined obstructive/restrictive disease in adulthood following CDH repair is not well categorized, and warrants careful preoperative attention. Early respiratory insufficiency also predisposes the CDH patient group to tracheostomy. Up to 7% of patients with CDH repair undergo tracheostomy.⁵

Patients may also have scoliosis, as well as chest wall defects, including pectus malformations, and chest dissymmetry. Dissymmetry affects approximately half of CDH patients,⁹ with pectus excavatum being the most common type of chest wall deformity,⁶ and more common among patients with large defects or patch repairs. Approximately one-fifth of CDH patients undergo pectus excavatum repairs. Patch repair is an independent risk factor for both hernia recurrence and early chest wall deformity. Patients repaired initially with a patch are approximately five times more likely to develop early chest wall deformity or CDH recurrence than primary repair counterparts.⁴ Scoliosis is found in up to 13% of CDH survivors. The scoliosis tends to curve toward the side of the hernia (concave), which can make approaches such as thoracoscopy more challenging. There is an association between the size of the patient's hernia defect and the observed degree of scoliosis.⁹

GERD affects up to 80% of CDH survivors.¹⁰ Several theories for the origin of GERD in CDH survivors exist. Abnormal anatomy at the level of the diaphragm (including an absent or attenuated left diaphragmatic crus) as well as medial traction from patch or primary repair can lead to abnormal function of the lower esophageal sphincter. In utero compression of the mediastinal esophagus by herniated viscera is also thought to be a contributor, which has been associated with mega-esophagus in up to 40% of CDH survivors.⁸ Long-term follow-up of patients with CDH has found esophagitis in up to 54% of individuals, along with presence of a hiatal hernia in as many as half of CDH survivors.⁶

Adults who underwent repair of a CDH are coming to the attention of general thoracic surgeons for the treatment of numerous sequelae of their congenital anomalies. This chapter provides a summary of the most common issues to be considered prior to operating on a patient who has survived this previously lethal congenital anomaly. With respect for the multisystem dysfunction, aberrant physiology, and continuity of surgical care of this unique patient group, general thoracic surgeons can be an integral part of the complex care these patients deserve.