How does a chest x-ray (CXR) show a hiatal hernia?

Radiographic Appearance of Hiatal Hernia on Chest X-ray

On chest X-ray, hiatal hernia typically appears as a retrocardiac air-fluid level or gas shadow with or without an air-fluid interface behind the heart. 1

Key Radiographic Findings

Hiatal hernias may demonstrate the following features on chest X-ray:

• Retrocardiac air-fluid level (most common finding)
• Gas bubble or air shadow behind the heart
• Widened mediastinum
• Abnormal cardiac silhouette
• Right interlobar artery measurement >15 mm in women or >16 mm in men (suggesting associated pulmonary hypertension) 2
• In large hernias, apparent cardiomegaly due to the superimposed hernia shadow 3

Diagnostic Accuracy

Chest X-ray has limited sensitivity for hiatal hernia detection:

• Sensitivity ranges from 2-60% for left-sided hernias and 17-33% for right-sided hernias 1
• Normal chest X-ray does not exclude hiatal hernia

Special Radiographic Signs

• Differential retrocardiac fluid level: The presence of two air-fluid interfaces at different heights in the retrocardiac region is particularly significant as it suggests not just a simple sliding hiatal hernia but potentially an intrathoracic gastric volvulus, which requires prompt attention 4

Types of Hiatal Hernias

The American College of Radiology classifies hiatal hernias into four types 1:

1. Type I (sliding) - most common (90% of cases)
2. Type II (paraesophageal)
3. Type III (combined)
4. Type IV (complex)

Limitations of Chest X-ray for Hiatal Hernia Diagnosis

• Chest X-ray alone is insufficient for definitive diagnosis
• Small hernias (<2 cm) are frequently missed
• Intermittent herniation may not be visible during the single moment captured by the X-ray
• Positioning of the patient can affect visualization

Superior Diagnostic Modalities

When hiatal hernia is suspected but chest X-ray is inconclusive:

• Barium swallow (upper GI series) provides the highest detection rate (76.8%) and is recommended as the first-line imaging study for structural evaluation 1, 5
• CT scan with IV contrast offers better visualization with sensitivity of 14-82% and specificity of 87% 1
• High-resolution manometry can detect subtle disruptions between the lower esophageal sphincter and crural diaphragm 6
• Upper endoscopy provides direct visualization but may miss mobile hernias 5

Clinical Correlation

Chest X-ray findings should be interpreted in the context of clinical symptoms:

• Gastroesophageal reflux disease (GERD) is commonly associated with hiatal hernias
• Large hiatal hernias can present with cardiac symptoms including angina and syncope due to cardiac compression 3
• Abnormal retrocardiac activity may be incidentally noted on cardiac imaging studies 7

Common Pitfalls

• Mistaking hiatal hernia for other mediastinal masses or cardiomegaly
• Failing to recognize the differential retrocardiac fluid level sign that may indicate gastric volvulus
• Relying solely on chest X-ray for diagnosis or exclusion of hiatal hernia
• Not correlating radiographic findings with clinical symptoms

Remember that while chest X-ray may be the initial imaging study performed due to nonspecific symptoms, its limitations necessitate additional diagnostic testing when hiatal hernia is clinically suspected.