Eventration of the diaphragm in infants

INTRODUCTION — Eventration of the diaphragm in infants is an uncommon disorder in which all or part of the diaphragmatic muscle is replaced by fibroelastic tissue, leading to a thinned and pliable central portion of the diaphragm. It is the result of either inadequate development (congenital) or atrophy (acquired) of the diaphragm.

The pathogenesis, clinical manifestations, diagnosis, and management of diaphragmatic eventration in infants will be discussed here. Eventration of the diaphragm in adults is discussed separately. (See "Diagnosis and management of nontraumatic unilateral diaphragmatic paralysis (complete or partial) in adults".)

EPIDEMIOLOGY — Accurate information regarding the incidence of infantile eventration of the diaphragm is challenging because the lesion is usually only identified in symptomatic patients and some affected infants may be asymptomatic for years or throughout their lives.

This was illustrated by the following case series:

●In the first report, 69 children were identified at a single tertiary center in the United States over a 20-year time period from 1953 to 1972 [1]. In this cohort, the diagnosis was made in 26 neonates, 17 infants between one month to one year of age, and the remaining 26 patients between 1 to 17 years of age.

●In the second study from a single Chinese tertiary center of 177 patients with congenital eventration of the diaphragm from 2000 to 2011, the diagnosis was made by three months in 71 patients (40 percent), from three months to one year in 58 patients (33 percent), and the remaining 41 patients between 1 to 18 years of age (23 percent) [2].

Case series demonstrate a male predominance with boys accounting for two-thirds of patients [1,2]. Congenital eventrations can either be an isolated defect or be associated with other developmental defects [2,3]. (See 'Congenital eventration' below.)

PATHOPHYSIOLOGY — Eventration of the diaphragm occurs when the diaphragmatic muscle is replaced by fibroelastic tissue and can be either congenital or acquired (due to injury of the phrenic nerve) [1,3-5]. In the previously mentioned case series from the United States, two-thirds of the cases were due to congenital eventration [1].

Eventration can also be classified based on the extent of the involvement of the diaphragm.

●Total (also referred to as diffuse) eventration involves the entire dome of the diaphragm.

●Partial (also referred to segmental) involves a localized segment of diaphragm lacks adequate muscle fibers.

Congenital eventration — Congenital eventration results from inadequate development of the diaphragmatic muscle or absence of the phrenic nerve. All or part of the diaphragmatic muscle is replaced by fibroelastic tissue resulting in either total (diffuse) or partial (segmental) involvement of the diaphragm [1,6-8]. The diaphragm retains its continuity and attachments to the costal margin. However, the weakened hemidiaphragm is displaced into the thorax, which can compromise breathing due to lung compression by abdominal contents.

Partial (segmental) defects occur in two-thirds of congenital cases, and most commonly affect the right hemidiaphragm [1,2].

Total or diffuse eventration occurring in the remaining one-third of cases tends to be unilateral. There is no difference in the incidence of eventration between right and left sides. In total congenital eventration, the diaphragm consists of a thin, diaphanous membrane that is attached peripherally to normal muscle. In contrast, in patients with congenital diaphragmatic hernia, the continuity between the diaphragm and the costal margin is disrupted.

In patients with congenital eventration, the incidence is two- to threefold greater in males than in females [2]. Congenital eventrations can be isolated, although they sometimes are associated with other developmental defects such as hypoplastic lung, cleft palate, congenital heart disease (CHD), situs inversus, or urogenital abnormalities (eg, undescended testicles) [1-3].

Acquired eventration — The most common cause of acquired eventration is injury to the phrenic nerve leading to diaphragmatic paralysis, resulting from either traumatic birth or thoracic surgery for CHD [1,3]. In these patients, the central tendon is normal and the diaphragm consists of normally-developed muscle. The loss of contractility leads to muscle atrophy and replacement with fibroelastic tissue (eventration) with elevation of the hemidiaphragm and a small phrenic nerve [4]. Both sides are affected equally. (See "Diaphragmatic paralysis in the newborn".)

When birth trauma is the underlying etiology, patients may also have brachial nerve palsy due to stretching of the nerve roots as a concomitant finding. (See "Neonatal brachial plexus palsy".)

CLINICAL MANIFESTATIONS — Limited data from case series demonstrate a wide spectrum of clinical manifestations varying from patients who are asymptomatic to those with severe respiratory distress [1,2,4]. The most common manifestations involve the respiratory and gastrointestinal tracts. Patients with partial defects usually have mild or no significant findings, whereas those with complete defects will have significant respiratory and gastrointestinal symptoms [1]. Typically, the most severely affected patients present as neonates [1]. The decisions regarding the need for intervention is based on the severity of clinical findings and their effects on the ability of the infant to feed and gain weight.

Asymptomatic patients present with an incidental finding of an elevated hemidiaphragm on a frontal or lateral view of a chest radiograph (image 1 and image 2).

Respiratory findings — Respiratory findings vary and include tachypnea, respiratory distress, use of accessory muscles of respiration, and cyanosis. Hypoxemia may result from several associated conditions, including lung hypoplasia, ventilation/perfusion mismatch due to atelectasis or pneumonia, or pulmonary hypertension with right-to-left intracardiac or ductal shunting [1,9,10]. Clinical severity increases with increasing compromise of lung function due to associated pulmonary hypoplasia and/or compression by abdominal contents that extrude into the hemithorax causing atelectasis. In the most severe cases, respiratory failure may require mechanical ventilation. There is also an increased risk of recurrent lower lobe bronchopneumonia due to regional lung compression and atelectasis [2,10].

Gastrointestinal findings — Gastrointestinal findings are more common for infants with complete defects and include vomiting and failure to thrive [1,2]. In some cases, there may be a scaphoid abdomen accompanied by bulging of the hemithorax as abdominal contents migrate into the hemithorax. In one case series of 69 patients, gastric volvulus was diagnosed in three patients who presented with repeated episodes of vomiting, poor feeding, and inadequate weight gain [1]. In these cases, the left-sided large defect allowed the stomach to rise above the elevated diaphragm resulting in rotation of the gastric fundus. (See "Intestinal malrotation in children".)

Associated conditions — Fryns syndrome [11], trisomy 18 [12], spinal muscular atrophy with respiratory distress [13], and congenital cytomegalovirus (CMV) infection [14] are also associated with congenital diaphragmatic eventration.

DIAGNOSIS — The diagnosis of eventration is typically suspected when a hemidiaphragm appears elevated on a frontal or lateral view on chest radiograph (image 1 and image 2). This usually occurs when a chest radiograph is being performed in a patient with respiratory distress or occasionally, as an incidental finding in an asymptomatic patient in whom a chest radiograph is being performed for another reason. The lateral view should demonstrate that the anterior and posterior diaphragmatic attachments are in the correct positions. Other radiographic findings that may be seen include atelectasis, elevated dome of the liver (right-sided involvement), and elevation of the stomach (left-sided involvement).

Chest ultrasound can be used to confirm the diagnosis. Ultrasound will demonstrate minimal or paradoxical diaphragm movement during breathing. With paradoxical movement, the diaphragm rises during inspiration and falls during expiration.

Although dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a diagnostic modality that holds some promise in the diagnosis of this condition, its lack of portability, time to complete the study, and cost are still obstacles that preclude its utility.

DIFFERENTIAL DIAGNOSIS — The primary differential diagnosis is congenital diaphragmatic hernia (CDH), which also presents with a radiologic finding of an elevated hemidiaphragm. However, the lateral chest radiograph in patients with eventration may demonstrate the anterior and posterior diaphragmatic attachments are in the correct positions distinguishing diaphragmatic eventration from herniation. Nevertheless, it may be difficult to differentiate between the two entities as there are similar radiographic findings in patients between the two conditions including cardiomediastinal shift, abnormal position of the stomach, and the appearance of bowel contents in the thorax and no bowel gas in the abdomen. Ultrasound may be useful in differentiating the two conditions, since the ultrasonographer is usually able to distinguish between an intact diaphragm/diaphragmatic tissue with an eventration and a defect in the diaphragm in patients with a diaphragmatic hernia with protruding bowel. However, the results of the study may not always be definitive [15], and thus the diagnosis in these unresolved cases is only made with direct visualization in the operating room.

Pulmonary sequestration and congenital pulmonary airway malformations may be considered as well; however, these entities are more likely to appear as lung masses. (See "Bronchopulmonary sequestration" and "Congenital pulmonary airway malformation".)

MANAGEMENT

Asymptomatic patients — In patients who are asymptomatic, no further evaluation or intervention is required [2].

Symptomatic patients — As noted above, most patients with severe defects present as neonates. Management initially focuses on supportive medical care with pulmonary function stabilization and administration of adequate nutrition. In some cases especially those with partial defects, initial medical management may be sufficient with resolution of symptoms and no need for surgical repair. However, a subgroup of patients will require surgical intervention due to persistent respiratory symptoms, poor growth due to inadequate intake, and significant gastrointestinal complications (eg, gastric volvulus).

The following management approach primarily focuses on patients who present as neonates as they are the most likely group of patients to present with symptoms and severe disease.

Medical management — General supportive care during the initial hospitalization includes the following:

●Respiratory support – Management is based on the infant's respiratory status.

•Oxygen supplementation is provided to maintain target peripheral oxygen saturation levels between 90 to 95 percent for preterm infants and above 95 percent for term infants. (See "Neonatal target oxygen levels for preterm infants".)

The initial supplementation of oxygen is provided through nasal cannula or hood. In our center, we commonly provide heated, humidified oxygen by nasal cannula at a low flow of 1 L/min or less. (See "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn", section on 'Low-flow nasal cannula'.)

•For infants who require >30 percent FiO₂ (fraction of inspired , additional respiratory support may be needed, by either the use of nasal continuous positive airway pressure (nCPAP, 6 to 8 cm H₂O pressure) or heated, humidified high-flow nasal cannula (HFNC) with a flow rate between 4 to 8 L/min. (See "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn", section on 'Continuous positive airway pressure' and "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn", section on 'High-flow nasal cannula'.)

•If the above steps are inadequate to maintain adequate oxygenation and/or if there is evidence of respiratory failure (arterial pH <7.2 and a PaCO₂ >65 mmHg), the infant is intubated and mechanical ventilation is provided using a volume-targeted mode. (See "Overview of mechanical ventilation in neonates".)

●Nutrition – Adequate nutrition is imperative to meet the metabolic needs of the infant. The level of respiratory support dictates how nutrition is provided.

•For the infant who is adequately supported with supplemental oxygen administrated by hood or nasal cannula, oral feeding can be initiated. However, if there is inadequate intake, gavage feedings should be provided.

•For infants who require more invasive respiratory support, nutrition is provided by gavage feedings or parenteral nutrition.

●Evaluation for associated congenital anomalies – A thorough physical examination should be performed to identify the presence of other anomalies, particularly cleft palate, congenital heart disease (CHD), situs inversus, or urogenital abnormalities [2,3]. At our center, cardiac echocardiography is routinely performed to detect any congenital heart defects. (See "Identifying newborns with critical congenital heart disease", section on 'Diagnostic approach'.)

Indications for surgical intervention — After the initiation of medical therapy, the following factors help guide when and if surgical correction is needed:

●Surgical plication is performed for the following patients:

•Infants with serious gastrointestinal complications such as gastric volvulus [1]. These patients may require emergency surgery.

•Infants who continue to require advanced respiratory support (CPAP, HFNC, or mechanical ventilation) one week after initiation of these interventions. For this group of patients, there appears to be little benefit in postponing diaphragmatic plication [5,16]. In particular, surgical plication is likely to benefit infants who respond to CPAP, as both interventions stabilize the diaphragm and increase functional residual capacity [17].

•Infants with inadequate nutritional intake after initiation of medical therapy [5,16]. This includes patients who are unable to feed orally or have inadequate oral intake and are dependent on gavage or parenteral nutrition for adequate nutrition.

•Infants with recurrent or life-threatening pneumonia [2].

●Surgical intervention is not needed if the patient responds to low-flow nasal cannula oxygen maintains adequate weight gain with oral feeding. It is likely that these infants will continue to improve and surgical intervention can be avoided [1].

●For infants with acquired diaphragmatic eventration, sufficient time should be given to allow recovery from neural injury. Most pediatric surgeons wait approximately three to four weeks after injury before moving to plication. For these patients, the above indications for surgical plication apply at the end of this time period.

Surgical plication

Procedure — Surgical repair consists of removing the slack in the diaphragm and fixing it to a lower position. This results in a flattened dome of the diaphragm, which increases resting lung volume and improves action of the intercostal and abdominal muscles during breathing.

Techniques for reducing slack of the diaphragm include plication, pleating, or invagination. The most effective method has yet to be determined [18,19].

Open thoracostomy has been the traditional surgical approach. However, video-assisted thoracic surgery (VATS) offers a less invasive method because it avoids the incision of the lower intercostal muscles, which may adversely affect ventilation [20]. VATS is becoming increasingly available. The choice is dependent on the expertise and experience of the staff at each center.

In a single-center retrospective study that included 108 infants and children with congenital diaphragmatic eventration who underwent surgical repair with open surgery (n=67) or VATS (n=41), VATS was associated with shorter operating time, less blood loss, fewer postoperative mechanical ventilation days, and shorter postoperative hospital stay [21]. Long-term follow-up demonstrated similarly improved preoperative symptoms in both groups.

Robot-assisted thoracoscopic plication is also being proposed to have technical advantages over the current VAT technique [22]. .

Timing — The optimal timing for surgical correction is uncertain. Surgical plication is seldom an emergency operation, and patients should be medically stabilized prior to operation. However, once the criteria for surgical plication are reached, the available evidence suggests that early intervention improves weight gain and growth and may prevent subsequent lung injury [5].

In our institution, surgical intervention is performed within the first 7 to 10 days after birth for newborns with congenital eventration who require advanced respiratory support (CPAP, HFNC, or mechanical ventilation) or who are unable to achieve adequate caloric intake orally. Patients with traumatic or postoperative eventration are typically supported until it is clear that there will be no further improvement of diaphragmatic function (neural recovery). This usually requires that the infant receives moderate to intensive medical support for three to four weeks before surgical plication.

Outcome — The outcome of patients who undergo surgical plication is generally excellent. This was best illustrated in a large Chinese case series of 177 patients with congenital eventration that reported the follow-up of 86 patients who underwent surgical plication at a mean age of 2.4 years (range 1.5 days to 6.3 years) [2]. Postoperative complications were reported in 13 patients (15 percent) and included pleural effusion and pneumonia. One month post-plication, symptoms were reported in only seven patients (tachypnea, vomiting, and recurrent respiratory infections). At one year follow-up, there were no reported symptoms in any patient. Other smaller case series have reported satisfactory diaphragmatic motion and pulmonary function studies following surgical plication [16,23].

Follow-up care — For many of these patients, particularly those who undergo surgical plication, follow-up care is initially performed by pediatric pulmonologists. The need for continued pulmonary follow-up care is based on whether there are ongoing pulmonary issues (eg, pulmonary hypoplasia).

SUMMARY AND RECOMMENDATIONS

●Pathophysiology – Eventration of the diaphragm in infants is an uncommon disorder that can be due to a congenital defect of inadequate development of the diaphragmatic muscle or absence of the phrenic nerves, or acquired due to injury of the phrenic nerve from birth trauma or thoracic surgery. Congenital eventration can be isolated or be associated with other anomalies. (See 'Pathophysiology' above.)

●Clinical manifestations – Clinical manifestations of diaphragmatic eventration range from asymptomatic patients to those with severe respiratory distress and failure. Other significant clinical manifestations include vomiting, poor feeding, and poor weight gain. Asymptomatic patients present with an incidental finding of an elevated hemidiaphragm on a frontal or lateral view of a chest radiograph (image 1 and image 2). (See 'Clinical manifestations' above.)

●Diagnosis – Diagnosis of eventration is usually suspected when there is an elevated hemidiaphragm on chest radiograph (image 1 and image 2). The diagnosis can be confirmed with chest ultrasound, demonstrating minimal or paradoxical diaphragmatic movement. (See 'Diagnosis' above and 'Differential diagnosis' above.)

●Management – Management of diaphragmatic eventration is based on the severity of clinical manifestations:

•Asymptomatic patients –Asymptomatic patients do not require further evaluation or intervention. (See 'Asymptomatic patients' above.)

•Symptomatic patients – Management for symptomatic patients includes initial general supportive care and the following:

-Supportive respiratory care is initiated to maintain oxygen saturation between 90 to 95 percent for preterm infants and >95 percent for term infants. Interventions range from supplemental oxygen via low-flow nasal cannula to mechanical ventilation for infants with respiratory failure. (See "Neonatal target oxygen levels for preterm infants" and "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn".)

-The administration of adequate nutrition is dependent on the respiratory status of the infant. In patients with significant respiratory distress or requiring advanced respiratory support (continuous positive airway pressure [CPAP] or mechanical ventilation), nutrition is provided by gavage feedings or parenteral nutrition. (See 'Medical management' above.)

●Indications for surgical repair – Patients with serious gastrointestinal complications (eg, gastric volvulus) require emergency surgical repair. In addition, we suggest surgical repair for infants who continue to require advanced respiratory support after one week and those with inadequate nutritional intake after starting medical therapy (Grade 2C). (See 'Surgical plication' above.)

●Timing of surgery – For patients with congenital defects who require advanced respiratory support and/or nutritional support, surgical plication is performed within the first 7 to 10 days after birth. Patients with acquired eventration are typically supported until it is clear that there will be no further improvement of diaphragmatic function. This usually requires that the infant receives moderate to intensive medical support for three to four weeks before surgical plication. (See 'Timing' above.)