Diaphragmatic hernia

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Diaphragmatic Hernia

Definition

Congenital diaphragmatic hernia (CDH) is a spectrum of developmental conditions characterized by a diaphragmatic defect that allows abdominal contents to protrude into the thoracic cavity, disrupting lung and pulmonary vascular development. — Sabiston Textbook of Surgery, p. 2675

Anatomy & Types

The diaphragm is embryologically derived from the septum transversum, pleuroperitoneal folds, abdominal wall components, and the dorsal mesentery. These structures begin fusing at 3–4 weeks of gestation, completely separating the pleural and peritoneal cavities by 9 weeks. Incomplete fusion produces distinct hernia types:

Type	Location	Frequency
Bochdalek	Posterior-lateral	70–75%
Morgagni	Anterior (retrosternal)	23–28%
Central	Central tendon	2–7%

Bochdalek hernias: Left-sided in ~85% of cases, right-sided in ~13%, bilateral in ~2%
Morgagni hernias are often asymptomatic until childhood or later

Incidence & Etiology

Incidence: ~1 in 2,000–5,000 live births
Most cases are sporadic, isolated, and non-syndromic
Exact etiology unknown; animal models implicate genetic, environmental, and nutritional factors
Associated anomalies (especially cardiac defects) seen in 25–50% of cases

Pathophysiology

Abdominal contents (stomach, bowel, and occasionally liver) herniate through the diaphragmatic defect and compress the ipsilateral developing lung, resulting in:

Pulmonary hypoplasia — smaller bronchi, reduced branching, decreased alveolar surface area; both lungs affected, ipsilateral more severely
Pulmonary hypertension — increased arteriolar smooth muscle thickness; vasculature is highly reactive to vasoactive factors
Mediastinal shift — compresses contralateral lung as well

The severity of pulmonary hypoplasia and pulmonary hypertension are the primary determinants of morbidity and mortality. — Sabiston Textbook of Surgery, p. 2675

Prenatal Diagnosis & Prognosis

Routine ultrasound can detect CDH as early as 15 weeks of gestation. Findings at 22–24 weeks include:

Mediastinal shift
Juxta-cardiac gastric dilatation
Polyhydramnios
Liver herniation into chest (right-sided CDH)

Prognostic tools:

Lung-to-Head Ratio (LHR): Ratio of contralateral lung area to head circumference
- LHR < 1.0 → poor prognosis
- LHR > 1.4 → ~100% survival
Observed/Expected LHR (O/E LHR): Normalized to gestational age
- O/E LHR < 25% → < 20% survival
Total lung volume > 45% of normal → predictive of survival
Intrathoracic liver herniation significantly worsens prognosis

Prenatal diagnosis is associated with worse survival because only larger defects are visible on fetal imaging. — Sabiston Textbook of Surgery, p. 2716

Clinical Presentation

Neonatal (typical):

Persistent respiratory distress at birth with grunting, dyspnea, retractions, and cyanosis
Characteristic "seesaw" (side-to-side) respiratory pattern
Scaphoid abdomen (bowel contents in thorax)
Bowel sounds auscultated in the chest
Displacement of heart tones
Significant preductal–postductal SpO₂ difference (right-to-left shunting)

Delayed presentation (10–20% of cases): Diagnosed after 24 hours with feeding difficulties, respiratory distress, or recurrent pneumonia.

Morgagni hernias: Often diagnosed incidentally in childhood or adulthood; most are asymptomatic. — Tintinalli's Emergency Medicine

Chest X-Ray

(A) Multiple gas-filled bowel loops in the left hemithorax with rightward mediastinal shift — classic CDH. (B) Left diaphragmatic eventration (arrow) from phrenic nerve injury-induced paralysis. — Sabiston Textbook of Surgery, p. 2675

Emergency Management

Immediate endotracheal intubation — bag-mask ventilation is contraindicated (inflates GI contents in chest, worsening compression)
Gentle ventilation: Rate 40–50 breaths/min, lowest peak inspiratory pressures that allow normal chest rise → prevents barotrauma to hypoplastic lungs
Permissive hypercapnia with gentle hyperventilation targeting PCO₂ 30–35 mmHg to reduce pulmonary vascular resistance
Large-bore orogastric tube (10F) on low continuous suction to decompress intrathoracic GI contents
Chest and ABG to confirm diagnosis and guide stabilization
Emergent referral to a pediatric specialty center — Tintinalli's Emergency Medicine

Definitive Management

Pulmonary hypertension treatment (pre-surgical stabilization):

High-frequency oscillatory ventilation (HFOV)
Inhaled nitric oxide (iNO)
ECMO (extracorporeal membrane oxygenation) for refractory cases
Vasodilators: PGE1, prostacyclin (PGI2), sildenafil (PDE-5 inhibitor), milrinone

Timing of surgical repair:

Defer 48–72 hours after initial stabilization (not emergent)
Allows treatment of pulmonary vascular lability before surgical stress
In patients on ECMO: timing of repair remains controversial

Surgical approach:

Open or minimally invasive (laparoscopic/thoracoscopic) repair
Primary closure when possible; larger defects require prosthetic patch repair
High-volume, protocolized centers have demonstrably improved outcomes

Overall survival: 65–90% — Sabiston Textbook of Surgery, p. 2675

Fetal Intervention: FETO

Fetal Endoluminal Tracheal Occlusion (FETO): Fetoscopic balloon placement in the trachea at 27–29 weeks to occlude airflow → accumulated lung fluid → stimulates lung growth.

Key trial results:

Severe CDH (O/E LHR < 25%): TOTAL trial showed 40% survival with FETO vs. 15% with expectant management — stopped early for efficacy
Moderate CDH (O/E LHR 25–34.9%): No significant survival benefit demonstrated
Complications: Preterm labor, PPROM, premature birth, fetal demise
Now offered at select fetal surgery centers in the US and Europe — Sabiston Textbook of Surgery, p. 2716

Summary Table

Feature	Detail
Most common type	Bochdalek (posterior-lateral)
Most common side	Left (85%)
Key pathophysiology	Pulmonary hypoplasia + pulmonary hypertension
Key prenatal marker	O/E LHR, liver herniation
Clinical sign	Scaphoid abdomen + bowel sounds in chest
Emergency treatment	ETT intubation (NOT bag-mask)
Definitive treatment	Surgical repair (defer 48–72 h)
Survival	65–90%

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