The development of the diaphragm is a complex process that involves contributions from multiple embryological structures. It forms primarily from the mesoderm and is completed by the eighth week of gestation.
- Origins:
- Septum Transversum: The main contributor to the central tendon of the diaphragm. It is derived from mesoderm and forms in the region of the future diaphragm.
- Pleuroperitoneal Membranes: These membranes grow and fuse with the septum transversum to close the pleuroperitoneal canal, a temporary opening between the thoracic and abdominal cavities.
- Dorsal Mesentery of the Esophagus: Contributes to the muscle of the diaphragm.
- Body Wall (Somatic Mesoderm): Contributes the muscular parts of the diaphragm, including the crura.
- Fusion: The diaphragm is formed by the fusion of these structures, with the pleuroperitoneal membranes contributing the majority of the muscle tissue, while the septum transversum forms the central tendon.
- Innervation: The phrenic nerve, originating from cervical spinal nerves (C3-C5), innervates the diaphragm. It descends alongside the heart and lungs, reaching the diaphragm by the end of the seventh week.
Types of Congenital Diaphragmatic Hernia (CDH):
Congenital diaphragmatic hernia occurs when there is an abnormality in the diaphragm’s development, allowing abdominal contents to herniate into the chest cavity. This defect may lead to pulmonary hypoplasia and other complications. The types of CDH are classified based on the location and nature of the hernia.
- Bochdalek Hernia:
- The most common type (about 85–90% of cases).
- Typically occurs on the left side of the diaphragm, in the posterior-lateral region.
- Involves the pleuroperitoneal membrane and is associated with the herniation of abdominal organs (such as the stomach, intestines, and spleen) into the chest cavity.
- Morgagni Hernia:
- Less common (approximately 2–5% of cases).
- Located anteriorly, typically on the right side of the diaphragm.
- Involves the foramen of Morgagni, an anterior gap in the diaphragm. Herniated contents are usually limited to the liver, bowel, and sometimes other organs.
- Central Hernia:
- Rare.
- Occurs at the central tendon of the diaphragm, leading to a defect in the muscle.
Current Recommendations for Management of Congenital Diaphragmatic Hernia (CDH):
The management of CDH focuses on stabilizing the neonate, addressing respiratory distress, and surgical repair:
- Initial Stabilization:
- Airway Management: Intubation and mechanical ventilation are often necessary due to the newborn’s respiratory distress.
- Oxygenation and Ventilation: High-frequency oscillatory ventilation (HFOV) may be used to improve oxygenation and reduce the risk of barotrauma.
- Sedation and Analgesia: Proper sedation and analgesia to reduce the stress of intubation and maintain comfort.
- Monitoring: Continuous monitoring of blood gases, oxygen saturation, and other vitals is essential.
- Extracorporeal Membrane Oxygenation (ECMO):
- Indicated in severe cases where conventional mechanical ventilation fails to adequately support pulmonary function.
- ECMO helps oxygenate the blood outside the body and allows for lung rest, promoting lung development.
- Surgical Repair:
- The defect should be repaired as soon as the neonate is stable enough for surgery.
- Primary Closure: If the defect is small, the diaphragm can be closed primarily.
- Patch Repair: Larger defects may require a synthetic or biologic patch for closure.
- Timing: Early repair is generally preferred; however, the timing depends on the infant’s condition.
- Postoperative Care:
- Ventilation: Continued mechanical ventilation after surgery until the infant can breathe independently.
- Nutritional Support: Parenteral nutrition may be necessary initially, with gradual introduction of enteral feeds.
- Follow-up: Infants should be followed up regularly for growth, development, and any residual pulmonary or gastrointestinal issues.
- Long-term Prognosis:
- Pulmonary Function: Pulmonary hypoplasia is a significant concern, and many infants require ongoing respiratory support in the immediate post-operative period.
- Gastrointestinal Complications: The risk of reflux and feeding difficulties may persist, requiring monitoring and management.
The overall survival rate has improved significantly with advances in neonatal care and surgical techniques, but the prognosis depends on the severity of the defect, associated anomalies, and the degree of pulmonary hypoplasia.