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Congenital Diaphragmatic Hernia (CDH) — Pediatric Surgery

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1. Definition & Overview

• Incidence: 1:2,000–5,000 births (some sources report 1:10,000–4:10,000)
• Survival: 65%–90% at major centers with modern management
• Isolated CDH: ~60% of cases; when associated with other anomalies, mortality >85%

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2. Embryology & Types

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

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3. Pathophysiology

1. Pulmonary hypoplasia — compression of the developing ipsilateral lung → fewer bronchial branches, reduced alveolar surface area; contralateral lung also affected
2. Abnormal pulmonary vasculature — increased arteriolar smooth muscle thickness; hypersensitive to vasoactive stimuli
3. Persistent pulmonary hypertension (PPH) — right-to-left shunting across PDA/PFO → severe hypoxemia
4. Mediastinal shift — compresses the contralateral lung

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4. Prenatal Diagnosis & Prognostication

Diagnosis

• Routine ultrasound detects ~2/3 of cases prenatally, as early as 15 weeks gestation
• Sonographic findings at 22–24 weeks:
  • Left-sided CDH: rightward cardiac/mediastinal shift, stomach/intestinal loops in chest, polyhydramnios
  • Right-sided CDH: liver in right chest, leftward mediastinal shift, harder to diagnose (liver echogenicity similar to fetal lung)
  • Liver herniation: difficult to distinguish sonographically; Doppler of umbilical vein/hepatic vessels helps

Differential Diagnosis (prenatal)

• CPAM, bronchogenic/enteric cysts, bronchopulmonary sequestration, bronchial atresia — no intra-abdominal organ displacement

Prognostic Markers

• Ratio of contralateral lung area to head circumference
• LHR < 1.0 → poor prognosis
• LHR > 1.4 → ~100% survival

• Compares measured LHR to reference values for gestational age
• O/E LHR < 25% → survival < 20%
• More reliable than absolute LHR across gestational ages

• Used as supplement to ultrasound
• Predictive of mortality, ECMO use, and oxygen requirement at 30 days

• Liver herniation ("liver up")
• Right-sided CDH
• Associated cardiac or chromosomal anomalies
• Stomach herniation

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5. Genetic Workup

• Genetic aberrations (trisomies, microdeletions, single-gene defects) occur in 6%–30% of CDH cases
• Array CGH / genome-wide comparative hybridization recommended
• ~30–40% of CDH cases have associated anomalies (congenital heart disease most common)
• Karyotyping + detailed fetal echo should be offered at diagnosis

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6. Fetal Intervention — Fetal Endoscopic Tracheal Occlusion (FETO)

• Open fetal CDH repair attempted in 1990s — no survival benefit over postnatal repair (even in severe cases) and increased prematurity risk
• Tracheal occlusion via metallic clip → tracheal stenosis, 15% survival
• Fetoscopic balloon (FETO) developed as minimally invasive alternative

• FETO offered at select fetal centers for severe left-sided CDH (liver up + O/E LHR <25%)
• Balloon inserted fetoscopically at 27–29 weeks, removed at 34 weeks (or emergently if preterm labor)
• Main risk: preterm premature rupture of membranes (PPROM), preterm delivery
• Balloon must be removed before delivery to allow airway

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7. Postnatal Clinical Presentation

• Respiratory distress at birth (tachypnea, grunting, cyanosis)
• Scaphoid abdomen (bowel in chest)
• Barrel-shaped chest
• Absent breath sounds on affected side (usually left)
• Bowel sounds auscultated in chest
• Heart sounds shifted to contralateral side
• NG tube coiling in chest on X-ray

• Multiple gas-filled bowel loops in the hemithorax
• Mediastinal/cardiac shift to contralateral side
• Contralateral lung compression
• Paucity of bowel gas in abdomen

• Can present weeks to years later with recurrent respiratory infections, GI symptoms, failure to thrive

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8. Initial Stabilization & Resuscitation

Airway & Ventilation

• Immediate intubation — avoid bag-mask ventilation (inflates herniated bowel → worsens lung compression)
• Gentle ventilation with low peak inspiratory pressures (PIP <25 cmH₂O) to prevent barotrauma to hypoplastic lungs
• Target: preductal SpO₂ 85%–95%, permissive hypercapnia (PaCO₂ 45–60 mmHg), preductal pH >7.25
• High-frequency oscillatory ventilation (HFOV) for refractory hypoxemia

Decompression

• Orogastric tube (Replogle) on suction — decompresses herniated bowel

Pulmonary Hypertension Management

• Inhaled nitric oxide (iNO): pulmonary vasodilator — first-line for PPH
• Sildenafil (PDE5 inhibitor): oral/IV pulmonary vasodilator
• Milrinone: inotrope + pulmonary vasodilator
• Avoid hypoxia, hypercarbia, acidosis, hypothermia — all worsen PPH

ECMO (Extracorporeal Membrane Oxygenation)

• Oxygenation index (OI) >40
• Unable to achieve preductal SpO₂ >85% despite iNO + maximal vent support
• VA-ECMO preferred (cardiac + respiratory support)
• VV-ECMO if cardiac function adequate
• Contraindications: severe pulmonary hypoplasia incompatible with survival, irreversible non-pulmonary conditions, gestational age <34 weeks / weight <2 kg (relative)
• Timing of surgery: can repair on ECMO or after decannulation — center-dependent

Target "Honeymoon Period"

• Pulmonary hypertension is controlled/stabilized
• Ventilator settings are improving or stable
• iNO weaning initiated
• Adequate urine output

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9. Surgical Repair

Timing

• NOT emergent — delay until physiologically stable (typically 24–72 hrs or longer)
• If on ECMO: may repair on ECMO to allow lung recovery

Approach

• Subcostal (transabdominal) incision — most common in neonates; allows reduction of all herniated contents, patch repair if needed
• Thoracotomy approach: used in some right-sided CDH or for thoracoscopic approach

• Increasingly used in hemodynamically stable, non-ECMO patients
• Advantages: less pain, faster recovery, smaller scars
• Risks: hypercapnia/acidosis from CO₂ insufflation in neonates with already compromised lungs, higher recurrence rates with patch repairs

Steps of Repair

1. Reduce herniated abdominal contents back into abdomen
2. Identify diaphragmatic defect margins
3. Primary repair (preferred) — interrupted non-absorbable sutures if edges can be approximated without tension
4. Patch repair (for large defects without adequate tissue) — using:
   • Gore-Tex (PTFE) — most common synthetic patch
   • Biological/acellular dermal matrix
   • Muscle flap (latissimus dorsi, abdominal wall)
5. Chest tube placement: controversial — most centers do NOT routinely place chest tubes to avoid mediastinal shift; if placed, kept on water seal (not suction)
6. Gastrostomy: may be placed for anticipated feeding difficulties

Primary vs. Patch Repair

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10. Postoperative Management

• Continue PPH management — do NOT expect immediate improvement
• Pulmonary hypertension may worsen 24–48 hrs post-repair (common)
• Continue iNO, sildenafil, milrinone as needed
• Extubation when off or minimal respiratory support
• Early enteral feeds (via NG or gastrostomy) once stable
• Watch for recurrence (especially with patch repairs)

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11. Complications & Long-Term Morbidity

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12. Morgagni Hernia

• Anterior (retrosternal) defect through the foramen of Morgagni
• Usually presents later (beyond infancy) — often incidental or with recurrent chest infections, GI symptoms
• Less physiologically severe than Bochdalek
• CXR: anterior mediastinal mass or air-fluid levels in right cardiophrenic angle
• Repair: laparoscopic approach preferred; generally excellent outcomes
• Primary suture repair usually sufficient

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13. Diaphragmatic Eventration

• Not a true hernia — thinned, non-muscularized diaphragm that paradoxically elevates with respiration
• Cause: phrenic nerve injury (birth trauma, cardiac surgery), developmental failure of muscularization
• May mimic CDH on imaging
• Management: plication of the diaphragm (open or thoracoscopic) when symptomatic

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14. Survival & Prognosis Summary

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• Sabiston Textbook of Surgery, 21st ed., Ch. 117 & 118 (pp. 2675–2716)
• Fanaroff & Martin's Neonatal-Perinatal Medicine, Ch. 34