Congenital Diaphragmatic Hernia (CDH)

Definition and Epidemiology

• Left-sided (Bochdalek): 85% of cases
• Right-sided: 13%
• Bilateral or complete agenesis: <2%
• Isolated CDH (no associated anomalies): ~60% of cases; if associated with other anomalies, mortality exceeds 85%

Embryology and Types

1. Septum transversum
2. Pleuroperitoneal folds
3. Components of the abdominal wall
4. Dorsal mesentery

Pathophysiology

• The ipsilateral lung is compressed and undergoes reduced bronchial branching and reduced alveolar surface area
• The contralateral lung is also affected by compression and intrinsic genetic factors (e.g., FOG2, GATA4 mutations)
• Lungs have smaller bronchi, fewer airway branches, and less alveolar area on both sides

• Pulmonary vascular smooth muscle is hypertrophied, with increased arteriolar wall thickness
• Arteriolar vasculature is hypersensitive to vasoactive stimuli
• This leads to right-to-left shunting (persistent fetal circulation) at the foramen ovale and ductus arteriosus

• Mediastinal shift compresses the contralateral lung and distorts cardiac anatomy
• Significant congenital heart defects co-occur in 25-50% of CDH patients
• Left ventricular hypoplasia may occur from reduced preload

• Trisomies, microdeletions, and single gene defects are all possible
• Array CGH detects abnormalities in ~6.3% of CDH cases
• Associated syndromes: Turner syndrome, Fryns syndrome, VACTERL association

Prenatal Diagnosis and Imaging

• Visualization of stomach, bowel, or liver in the thorax
• Rightward cardiac/mediastinal shift (in left CDH)
• Polyhydramnios
• Absence of the normal stomach bubble below the diaphragm

• Congenital pulmonary airway malformation (CPAM)
• Bronchopulmonary sequestration
• Bronchogenic/enteric cysts
• Mediastinal teratoma

Prognostic Assessment

1. Lung-to-Head Ratio (LHR)

2. Observed-to-Expected LHR (O/E LHR)

Clinical Presentation (Postnatal)

• Persistent respiratory distress at birth
• "Seesaw" or "rocking" respiratory pattern due to severely hypoplastic ipsilateral lung
• Persistent cyanosis and oxygen desaturation
• Scaphoid abdomen (hallmark - abdominal organs are displaced into chest)
• Bowel sounds audible in the chest
• Displacement of heart tones away from side of hernia
• Preductal and post-ductal SpO2 difference indicating right-to-left shunting

Radiological Findings

• Gas-filled bowel loops within the hemithorax
• Mediastinal/cardiac shift to the contralateral side
• Absence or reduction of bowel gas in the abdomen
• Absence of visible diaphragmatic outline

Management

A. Emergency Stabilization (Birth/ER)

1. Immediate endotracheal intubation - avoid bag-mask ventilation
2. Large-bore (10F) orogastric tube on continuous low suction - decompress herniated bowel
3. Gentle ventilation: rate 40-50 bpm, lowest peak inspiratory pressure that allows normal chest rise (avoid barotrauma to hypoplastic lungs)
4. Target PaCO2 30-35 mmHg (permissive hypercapnia is also acceptable) to reduce pulmonary vascular resistance
5. Pulse oximetry monitoring pre- and post-ductal

B. ICU Stabilization - "Gentilation" Protocol

• High-frequency oscillatory ventilation (HFOV) - preferred in severe cases
• Permissive hypercapnia (limiting peak inspiratory pressures)
• Target pH 7.35-7.45, preductal SpO2 >85%

• Inhaled nitric oxide (iNO) - selective pulmonary vasodilator
• Sildenafil (PDE-5 inhibitor) - oral/IV
• Prostacyclin (PGI2) and PGE1 (prostaglandins)
• Milrinone - inotrope + pulmonary vasodilator
• Inotropes for cardiac dysfunction

C. Fetal Intervention - FETO

• A balloon is inserted into the fetal trachea under fetoscopic guidance between the vocal cords and carina
• Typically performed at 27-29 weeks gestation
• Tracheal occlusion prevents lung fluid egress → lung fluid accumulation → lung growth
• Balloon is retrieved fetoscopically or percutaneously at ~34 weeks
• If removal fails, an EXIT procedure at delivery ensures airway patency

• Severe CDH (O/E LHR <25%): FETO improved survival to 40% vs. 15% with expectant management (stopped early for efficacy)
• Moderate CDH (O/E LHR 25-35%): FETO at 30-32 weeks showed no survival benefit over expectant management

D. Surgical Repair

1. Herniated viscera (stomach, bowel, occasionally liver/spleen) are reduced back into the abdomen
2. The diaphragmatic defect is assessed:
   • Small defect: Primary repair with interrupted non-absorbable sutures
   • Large defect: Patch repair using Gore-Tex (PTFE) or Silastic/conical patch
3. A hernia sac may be present - it can be excised or plicated
4. Chest drain placed to expand lung

• Avoid bag-mask ventilation pre-intubation
• High risk of pneumothorax (ipsilateral or contralateral) from barotrauma to hypoplastic lungs
• Avoid hypoxemia and excessive hypercapnia to prevent pulmonary hypertension crisis
• Deep general anesthesia to blunt stress response

Outcomes and Survival

• Overall survival: 65-90% at specialized centers
• Prenatal diagnosis is paradoxically associated with worse prognosis (larger defects are more visible prenatally)
• Total lung volume >45% of normal is predictive of survival

Summary

• Sabiston Textbook of Surgery, 21st Ed., pp. 2675-2676, 2716
• Creasy & Resnik's Maternal-Fetal Medicine, pp. 776-778
• Bailey & Love's Short Practice of Surgery, 28th Ed., p. 1763
• Tintinalli's Emergency Medicine
• Miller's Anesthesia, 10th Ed.
• Pye's Surgical Handicraft, 22nd Ed.