Introduction
Congenital diaphragmatic hernia (CDH) is a developmental defect of the diaphragm allowing herniation of abdominal viscera into the thoracic cavity, resulting in pulmonary hypoplasia and pulmonary hypertension.
It is an important cause of neonatal respiratory distress, often presenting immediately after birth.
Imaging plays a crucial role in:
- Antenatal detection
- Postnatal diagnosis
- Determining side, type, and contents of hernia
- Assessing lung hypoplasia and associated anomalies
Types of Congenital Diaphragmatic Hernia
- Bochdalek hernia (Posterolateral) – ~85–90%, usually left-sided
- Morgagni hernia (Anteromedial) – rare
- Central diaphragmatic eventration / defects
Antenatal Imaging
1. Prenatal Ultrasound (Primary Modality)
Key USG Findings:
- Absent or poorly visualized diaphragm
- Abdominal organs within thoracic cavity:
- Stomach (common in left-sided CDH)
- Bowel loops
- Liver (right-sided CDH)
- Mediastinal shift to opposite side
- Small abdominal circumference
- Polyhydramnios (due to esophageal compression)
Signs of Pulmonary Hypoplasia:
- Reduced lung area
- Compression of ipsilateral lung
Prognostic USG Parameters:
- Lung-to-head ratio (LHR)
- Observed-to-expected LHR (O/E LHR)
2. Fetal MRI
Advantages:
- Superior soft tissue contrast
- Accurate assessment of lung volumes
- Better delineation of liver herniation
MRI Findings:
- Herniation of abdominal viscera into thorax
- Compressed hypoplastic lung
- Precise calculation of total fetal lung volume
- Differentiation between liver and bowel
Prognostic Value:
- Lower lung volume → poorer prognosis
Postnatal Imaging
1. Chest Radiograph (First-Line Imaging)
Typical X-ray Findings:
- Multiple air-filled bowel loops in hemithorax
- Absence of normal diaphragmatic contour
- Mediastinal shift to contralateral side
- Compressed ipsilateral lung
- Scaphoid abdomen (reduced abdominal gas)
Right-sided CDH:
- Homogeneous soft tissue opacity due to liver herniation
- May mimic lung consolidation
2. Ultrasound (Postnatal)
Role:
- Useful in unstable neonates
- Confirms presence of abdominal contents in thorax
- Differentiates CDH from diaphragmatic eventration or lung pathology
USG Findings:
- Absent diaphragmatic continuity
- Peristaltic bowel loops or liver within thorax
- Reduced lung tissue on affected side
3. CT Scan (Limited Role)
Indications:
- Atypical cases
- Preoperative anatomical clarification (rare)
CT Findings:
- Defect in diaphragm
- Herniation of abdominal viscera
- Lung hypoplasia
- Mediastinal shift
⚠️ CT is generally avoided in neonates due to radiation
4. MRI (Postnatal – Selected Cases)
- Superior evaluation of diaphragmatic defect
- Excellent soft tissue characterization
- Assessment of lung volume and associated anomalies
Differential Diagnosis on Imaging
- Congenital pulmonary airway malformation (CPAM)
- Eventration of diaphragm
- Pulmonary sequestration
- Bronchogenic cyst
- Large pleural effusion
Associated Anomalies
- Cardiac anomalies (most common)
- Neural tube defects
- Genitourinary anomalies
- Chromosomal abnormalities (Trisomy 18, 21)
Imaging-Based Prognostic Factors
- Degree of lung hypoplasia
- Liver herniation (poor prognostic factor)
- Side of hernia (right-sided worse prognosis)
- O/E lung-to-head ratio
- Presence of associated anomalies
Comparison of Imaging Modalities
| Modality | Role |
|---|---|
| Antenatal USG | Screening & diagnosis |
| Fetal MRI | Prognosis & lung volume |
| Chest X-ray | Postnatal confirmation |
| Ultrasound | Bedside assessment |
| CT/MRI | Selected pre-op cases |
Key Exam Points
- Bochdalek hernia is the most common type
- Left-sided CDH is more frequent
- X-ray shows bowel loops in chest + mediastinal shift
- Antenatal MRI helps in prognosis
- Pulmonary hypoplasia determines outcome
Conclusion
Imaging plays a pivotal role in the diagnosis and management of congenital diaphragmatic hernia. Antenatal ultrasound and fetal MRI enable early detection and prognostication, while postnatal chest radiography confirms diagnosis and guides management. Accurate imaging assessment significantly influences clinical outcome in affected neonates.
