Congenital diaphragmatic hernias

A diaphragmatic hernia is the protrusion of intra-abdominal contents through an abnormal opening in the diaphragm. Congenital diaphragmatic hernias (CDH) are a common developmental defect, resulting from an incomplete fusion of embryonic components of the diaphragm. Left-sided postero-lateral diaphragmatic defects (Bochdalek hernias) are the most common, followed by anterior defects (Morgagni hernias). About 50% of babies with CDH have additional congenital malformations. CDH are often diagnosed prenatally on routine antenatal ultrasound. Neonates with CDH present postnatally with respiratory distress and a characteristic absence of breath sounds in the ipsilateral chest. The respiratory distress is due to severe pulmonary hypoplasia, persistent pulmonary hypertension of the newborn (PPHN), and poor surfactant production, all of which are typical characteristics of CDH. Postnatal diagnosis is confirmed on a chest x-ray which reveals abdominal contents in the thorax. Neonates with CDH should be medically stabilized (mechanical ventilation, inotropic support, gastric decompression) before surgical repair, which is then done within the first week of life. Also see our article “Acquired diaphragmatic hernias”.

• Incidence: one in 3000 live births

Epidemiological data refers to the US, unless otherwise specified.

• The diaphragm consists of two parts: ^[1]
  • The peripheral muscular part: made up of radial muscle fibers
  • A central tendinous part: a flat aponeurosis into which the peripheral muscle fibers converge and insert
• Embryologically, the diaphragm is derived from four embryonic structures ^[2]
  • Septum transversum
    • Forms at four weeks of gestation as an incomplete diaphragm centrally separating the pleural and peritoneal cavities
    • Develops into the central tendon of the diaphragm
  • Pleuroperitoneal membranes
    • At the 5^th week of gestation, pleuroperitoneal membranes form lateral to the central tendon, on either side.
    • They fuse with the septum transversum and the mesentery of the esophagus to complete the partition between the pleural and peritoneal cavities.
    • The left side fuses later, possibly explaining why most CDH are left-sided.
  • Dorsal mesentery of the esophagus: develops into the diaphragmatic crura
  • Mesoderm of the body wall: forms the peripheral rim of the diaphragm

• Impaired development and/or fusion of embryonic structures (pleuroperitoneal membrane) → defect in the diaphragm persists during fetal development → displacement of abdominal contents into the pleural cavity ; → compression of lung tissue; → pulmonary hypoplasia
• Types
  • Failure of fusion of the septum transversum postero-laterally with the pleuroperitoneal membranes → Bochdalek hernia.
    • Most common CDH, accounting for 90% of cases.
    • Postero-lateral (lumbocostal) CDH (85% are left-sided)
  • Failure of fusion of the septum transversum anteriorly with the sternum and ribs → Morgagni hernia (Morgagni-Larrey hernia)
    • Rare: < 5% of CDH
    • Anterior (sternocostal/parasternal) CDH (90% are right-sided)
    • Infants with Morgagni hernia often present late.

Because the liver protects the right hemidiaphragm, diaphragmatic hernias most commonly occur on the left side!

^[3][4]

• Presentation depends on the degree of pulmonary hypoplasia and pulmonary hypertension
• Respiratory distress (e.g., nasal flaring, tachypnea, cyanosis, intercostal retractions, grunting)
• Barrel-shaped chest, scaphoid abdomen (concave anterior abdominal wall), and auscultation of bowel sounds in the chest
• Absent breath sounds on the ipsilateral side
• Mediastinal shift: shift of heart sounds/apex beat to the right side
• Possible syndromic dysmorphism (e.g., craniofacial, spinal dysraphism, cardiac)

• Antenatal ultrasound^[5]: most cases are diagnosed on routine antenatal ultrasound^[3]
  • Fluid-filled stomach/bowel seen in the thorax
  • Peristalsis may also be noted in the chest, confirming the diagnosis.
  • Esophageal compression can cause polyhydramnios
  • Hydrops fetalis may also be seen in severe cases
• Chest x-ray
  • Abdominal contents, air/fluid-filled bowel, and poorly aerated lung in the ipsilateral hemithorax
  • Mediastinal shift to the right and compression of the contralateral lung
  • In doubtful cases, a naso-gastric tube is inserted and a chest radiograph is taken: the feeding tube will be seen in the thorax.
  • In right-sided CDH: the liver appears as an intrathoracic soft tissue mass + absence of the normal intra-abdominal liver shadow

Avoid pleurocentesis in a suspected diaphragmatic hernia because of the risk of bowel perforation, which is suggested by bile in the chest tube!

• Prenatal CDH
  • Congenital diaphragmatic eventration: not a true hernia, but rather an outpouching or abnormal elevation of a portion of the hemidiaphragm; no break in diaphragmatic tissue
  • Bronchogenic cysts
    • Clinical features
      • Usually asymptomatic
      • In some cases, failure to drain can cause airway compression with significant respiratory distress or recurrent respiratory tract infections.
    • Diagnostics
      • Chest x-ray: discrete, round, and sharply defined fluid-filled densities; infection indicated by air inclusions
    • Pathogenesis: abnormal budding of the ventral foregut → dilation of the terminal or large bronchi → unilateral or bilateral unilocular cysts
  • Congenital pulmonary airway malformation (CPAM) ^[6]
    • Previously known as congenital cystic adenomatoid malformation (CCAM)
    • Features cystic and/or adenomatous pulmonary lesions
    • Diagnosed via prenatal ultrasound
    • Management involves steroids and drainage and/or surgical removal of cysts
  • Pulmonary agenesis
  • Tumors in the anterior/posterior mediastinum (e.g., teratomas, neurofibroma, pheochromocytoma, neuroblastoma, etc.)
  • Pulmonary sequestration lung tissue that is not connected to the tracheobronchial tree
• Postnatal CDH
  • Other causes of pulmonary hypoplasia (e.g., oligohydramnios, renal hypoplasia)
  • Other causes of pulmonary hypertension of the newborn (e.g., meconium aspiration)

The differential diagnoses listed here are not exhaustive.

• Prenatally diagnosed CDH: antenatal glucocorticoids
• Postnatal therapy
  • Initial medical resuscitation
    • Correction of hypoxia
      • Intubation and mechanical ventilation: indicated in all infants with CDH
      • Extracorporeal life support (ECLS): A heart-lung bypass pump that circulates the infant's blood through an artificial lung and then back into the bloodstream.
        • Indicated in infants who do not improve on mechanical ventilation/have persistent hypoxia or acidosis
        • Contraindicated in infants with large/expanding intracranial hemorrhages, as ECLS requires anticoagulation
    • Gastric decompression: insertion of a nasogastric tube and continuous suction
    • Inotropic support may be required to maintain blood pressure
    • Surfactant administration: in infants born < 34 weeks of gestation and x-ray findings suggesting neonatal respiratory distress syndrome
  • Surgical repair (thoracotomy or laparotomy)
    • Indicated in all cases of CDH
    • Timing: after the infant is stabilized, often after 24–48 hours
    • Procedure: reduction of the hernial contents and primary closure of the defect

• Bowel complications: obstruction, strangulation, incarceration, ileus, ulceration, perforation

We list the most important complications. The selection is not exhaustive.