• Clinical science

Congenital diaphragmatic hernias

Abstract

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.

Epidemiology

  • Incidence: one in 3000 live births[1]
  • ∼ 8% of major congenital anomalies
    •

Epidemiological data refers to the US, unless otherwise specified.

Embryology of the diaphragm

  • The diaphragm consists of two parts:[2]
    • 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[3]
    • Septum transversum
    • Pleuroperitoneal membranes
      • At the 5th 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

Etiology

  • 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)
      • The stomach and intestines herniate through the left-sided defect.
        •
      • The liver and the large bowel herniate through the right-sided defect.
        •
    • 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)[4]
      • Infants with Morgagni hernia often present late.
    • The omentum, the colon, and the liver are common hernial contents.
      •
    • Central CDH
      • Least common type
      • Defect lies in the central tendinous portion of the diaphragm.

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

References:[3][5][6]

Clinical features

  • Presentation depends on the degree of pulmonary hypoplasia and pulmonary hypertension Rare cases of CDH presenting in older children/adults have been reported.
  • Respiratory distress (e.g., nasal flaring, tachypnea, cyanosis, intercostal retractions, grunting)
  • Barrel-shaped chest, scaphoid abdomen; , and auscultation of bowel sounds in the chest[4]
  • 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)

References:[7][8]

Diagnostics

  • Antenatal ultrasound[9]
    • Fluid filled stomach/bowel maybe seen in the thorax adjacent to the lung
    • 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[7]
    • Abdominal contents, air/fluid-filled bowel, and poorly aerated lung in the ipsilateral hemithorax
    • Mediastinal shift to the right + 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
  • Magnetic resonance imaging (MRI)
    • Used pre-operatively, to gauge fetal lung volume
    • Can help assess postnatal mortality

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

Differential diagnoses

References:[7]

The differential diagnoses listed here are not exhaustive.

Treatment

Complications

  • Bowel complications: obstruction, strangulation, incarceration, volvulus, ileus, ulceration, perforation
  • Post-operative
    • Relapse
    • Gastric inlet stenosis
    • Gas-bloat syndrome
    •

References:[1]

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