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    Drugs & Diseases>Pediatrics: Surgery

    Diaphragmatic Hernias

    Updated: Nov 22, 2024
    • Author: S Christopher Derderian, MD, FAAP; Chief Editor: Eugene S Kim, MD, FACS, FAAP  more...
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    Overview

    Practice Essentials

    Diaphragmatic hernia is a condition in which intra-abdominal contents herniate into the thoracic cavity via a defect in the diaphragm. The defect may be congenital or acquired (eg, as a consequence of blunt or, less often, penetrating trauma). Congenital diaphragmatic hernia (CDH) is considerably more common than acquired diaphragmatic hernia (ADH) and is the primary focus of this article.

    CDH is often diagnosed on 20-week screening antenatal ultrasonography (US). [1] Left-side defects account for 80-85% of cases and right-side defects for 10-15%; bilateral defects are rare, accounting for only 1-2% of cases. The majority (90%) of defects are posterolateral and are referred to as Bochdalek hernias. The remaining 10% are anteromedial and are referred to as Morgagni hernias. [2, 3] Because CDH compresses the lung during a critical time of lung development, infants with this condition are at increased risk for the development of pulmonary hypoplasia and pulmonary hypertension.

    CDH was first described in 1679 in a postmortem examination of a 24-year-old man. [4] Surgical repair of a CDH was first attempted in 1888 in a 19-year-old who presented with respiratory distress and an acute abdomen; findings from clinical examination prompted a laparotomy that revealed the diaphragmatic defect. The first successful repair was performed in 1905 in a 9-year-old male; after reduction of the herniated content, the diaphragmatic defect was closed through a midline laparotomy incision. Approximately two decades later, the first outcomes associated with CDH were reported, with a 58% mortality among patients who underwent surgical intervention.

    It was not until 1940 that Ladd and Gross based their diagnosis of CDH on history, physical examination, and chest radiographic findings. [4] They advocated early surgical intervention (≤ 48 hr after diagnosis). Gross also described a two-stage closure of the abdominal wall in challenging cases, with closure of the skin and subcutaneous fascia in the initial surgery and closure of the abdominal wall 5-6 days later. In 1950, Koop and Johnson suggested the transthoracic approach as a means of closing the defect under more direct vision.

    As surgical expertise has improved, innovative strategies have been developed to address large diaphragmatic defects and agenesis of the hemidiaphragm. These techniques have included the use of rotational muscle flaps, perirenal fascia, and synthetic patch repairs.

    Over the past few decades, improved understanding of the cardiopulmonary sequelae of CDH has shaped the management of this complex patient population, and this development has resulted in better outcomes. CDH is no longer considered a primarily surgical disease but, rather, a disease associated with pulmonary hypoplasia, pulmonary hypertension, and an increased susceptibility to ventilation-induced lung injury.

    Contemporary management of CDH emphasizes the importance of the management of pulmonary hypoplasia and persistent pulmonary hypertension. Various gentle alveolar recruitment strategies are employed, and a nonurgent approach is taken to operative treatment, once therapies for pulmonary hypertension have been initiated. Urgent surgical repair is almost never necessary and may induce a pulmonary hypertension crisis.

    Next: Anatomy

    Anatomy

    The diaphragm is a musculotendinous structure that plays a crucial role in pulmonary mechanics. It consists of a continuous convex muscle surrounding a central tendon, with peripheral attachments that include the xiphoid process, ribs, costal cartilage, and vertebral bodies.

    The diaphragm functions to regulate the thoracic volume by promoting pressure changes as it contracts and relaxes and is particularly influential with respect to forced vital capacity (FVC) and maximal inspiratory pressure (MIP). When the diaphragm contracts, it generates negative thoracic pressure, drawing air into the lungs; this ultimately results in gas exchange at the alveolar-capillary beds. Conversely, as it relaxes, pressure increases, promoting expulsion of carbon dioxide. In patients with CDH, the anatomic defect results in disruption of these physiologic processes.  

    Relevant embryology

    During embryology, the earliest diaphragm precursor is seen at week 4 of gestation, and it is derived from four embryonic structures: septum transversum, pleuroperitoneal membranes, mesoderm of the body wall, and esophageal mesenchyme. The septum transversum is located ventrally and eventually develops into the central tendon. Pleuroperitoneal membranes are dorsolateral, and crura of the esophageal mesentery are dorsal. [5]  By week 8 of gestation, pleural and peritoneal cavities are separated. Muscularization begins with migration of phrenic nerve axons and recruitment of myoblasts to form a mature diaphragm. [5, 6]    

    Bochdalek hernias are thought to be caused by an embryologic failure in the fusion of the pleuroperitoneal folds and the transverse septum with the intercostal muscles. Morgagni hernias, on the other hand, are believed to be caused by a defect in the union of the transverse septum and lateral body wall. [2, 3]  

    Most authors have postulated that CDH develops from failure of diaphragm muscularization prior to closure of the pleuroperitoneal canals, resulting in diaphragmatic weakness prone to herniation. Others have suggested that abnormal lung development results in a weakened mesenchymal plate with impaired diaphragm fusion. Disruptions or mutations in myofibroblasts derived from pleuroperitoneal folds may also play a role, ultimately causing abnormal diaphragm development. [6, 7, 8]  Further research into the pathogenesis is needed to facilitate the potential development of in-utero therapies targeted at failed embyogenesis.  

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    Pathophysiology

    Congenital diaphragmatic hernia

    CDH occurs early in fetal development as a consequence of incomplete fusion of diaphragmatic structures leading to herniation of intra-abdominal organs into the thoracic cavity. Although infants born with CDH suffer from sequelae related to multiple organs, the leading causes of morbidity and mortality in these patients are the cardiopulmonary consequences of the condition—specifically, pulmonary hypoplasia and pulmonary hypertension. 

    The herniation of intra-abdominal organs during critical stages of lung development results in significantly reduced bronchial branching, alveolar surface area, and pulmonary vascularization—hallmark pathologic findings in pulmonary hypoplasia. Whereas normal airway development results in approximately 23-25 branched divisions, individuals affected by CDH often only have 12-14 divisions within the ipsilateral lung and 16-18 within the contralateral lung. [9, 10]  This disruption of bronchial branching is associated with impaired alveolar development and pulmonary hypoplasia. [11]  

    Abnormal vascular smooth-muscle development is another hallmark feature associated with CDH. Specifically, pulmonary arterial smooth-muscle hypertrophy results in increased pulmonary artery resistance and consequently in pulmonary hypertension. [11, 12]  Pulmonary hypertension may lead to sustained fetal circulation postnatally, with right-to-left shunting, progressive hypoxemia, hypercarbia, and acidosis. There is an association between the severity of pulmonary hypertension and the morbidity and mortality of CDH, with high mortality reported among those with persistent suprasystemic pulmonary artery pressures beyond 21 days of life. [13, 14]

    Acquired diaphragmatic hernia

    In ADH, the pathophysiology includes circulatory and respiratory depression secondary to impaired diaphragmatic function, intrathoracic presence of abdominal contents leading to compression of the lungs, shifting of the mediastinum, and cardiac compromise. [15] If the hernia is relatively small, it may not be identified until months or years after the initial insult, when the patient presents with dyspnea, strangulated intra-abdominal organs, or nonspecific gastrointestinal (GI) complaints.

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    Etiology

    Congenital diaphragmatic hernia

    The etiology of CDH is largely unknown but is probably multifactorial. However, there are several reported maternal risk factors for CDH have been reported, including the following [16] :

    • Advanced age
    • Gestational diabetes
    • Gestational hypertension
    • Low body mass index (BMI)
    • Tobacco use
    • Alcohol use 

    Multiple studies are currently investigating genetic factors leading to CDH; there is a known association between CDH and certain chromosomal abnormalities. An estimated 60% of CDH cases are isolated (ie, occur in healthy term pregnancies), whereas 40% are nonisolated (ie, occur in infants with an associated chromosomal or other structural anomaly). [17]  Disorders commonly associated with CDH include the following [18] :

    • Aneuploidies (trisomy 13, 18, 21)
    • Congenital heart defects
    • Musculoskeletal, craniofacial, and nervous system deformities

    Inheritance of CDH is also poorly understood, with familial occurrence of CDH estimated to be about 2%. [19]

    Abnormalities in the retinoid signaling pathway have been hypothesized to contribute to the etiology. [20, 21] The earliest link was observed when 25-40% of the offspring of rat dams fed a vitamin A–deficient diet developed CDH, and the proportion of affected pups decreased when vitamin A was reintroduced into the diet in midgestation. [22] Subsequently, vitamin A was found to decrease the incidence and severity of CDH caused by exposure to the herbicide nitrofen in utero. [23] Two clinical studies demonstrated that plasma retinol and retinol-binding protein levels in cord blood were significantly lower in newborns with CDH than in control subjects, independent of maternal retinol levels. [24, 23]

    To achieve a better understanding of the underlying etiology of CDH, further research will be required.

    Acquired diaphragmatic hernia

    ADH is most commonly caused by blunt or (less frequently) penetrating trauma. Motor vehicle accidents (MVAs) are the leading cause of blunt diaphragmatic injuries, whereas gunshot or stab wounds are the leading cause of penetrating diaphragmatic injuries. Rarer causes of traumatic diaphragmatic rupture include the following:

    • Labor in women who have previously undergone diaphragmatic hernia repair [25]
    • Barotrauma during underwater dives in patients who have previously undergone Nissen fundoplication [26]
    • Liver transplantation (particularly in children) [27, 28, 29]

    These rare cases occur more frequently on the left side than on the right (68.5% vs 24.2%), presumably because of the liver protection and increased strength afforded by the right hemidiaphragm.

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    Epidemiology

    CDH has been estimated to occur in 1 in 5000 live births in the United States [1] and approximately 2.3 per 10,000 live births globally. Prevalence varies across geographic regions, and estimates may include both isolated and nonisolated cases. [30, 31]  It is likely that prevalence is underestimated, given that stillbirth and pregnancy termination are often excluded. Another challenge to obtaining accurate figures is variation in antenatal detection, which has dramatically improved over time but remains dependent on geographical location. Such challenges are likely to result in underreporting or missing data in epidemiologic studies. [10]

    ADH is relatively uncommon. Fewer than 1% of patients who sustain trauma have an associated diaphragmatic injury. [32] ​ Most cases occur in the third decade of life. The male-to-female ratio is 4:1.

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    Prognosis

    Historically, mortality for those with a CDH has been in the range of 25-35%, and even higher figures have been reported when termination of pregnancy and fetal loss in late gestation (~8%) were included. With advances in neonatal care, mortality for CDH has decreased substantially, falling to 15-20% in most centers [33]  and to 5-10% in higher-functioning centers. This decrease is probably due to better ventilation practices, with reduced ventilator-induced lung injury, and to better control of postnatal infection, especially central line–associated bloodstream infection (BSI) and ventilator-associated pneumonia. [34]  

    In all studies, the only reliable predictor of mortality has been the presence of associated anomalies (see Etiology), which increases mortality to the range of 70-85%. Mortality in infants requiring extracorporeal membrane oxygenation (ECMO) remains around 50% and has stagnated at this level for the past two decades. [35]   

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