What is the recommended imaging modality for suspected diaphragmatic hernia?

Imaging for Diaphragmatic Hernia

CT scan is the gold standard for diagnosing diaphragmatic hernia, with a sensitivity of 14-82% and specificity of 87%, and should be performed with contrast enhancement of both chest and abdomen in stable patients with suspected diaphragmatic hernia. 1

Initial Diagnostic Approach

• Chest X-ray (both anteroposterior and lateral views) is recommended as the first diagnostic study in patients without trauma history presenting with respiratory symptoms 1, 2
• Despite advances in imaging technology, chest X-ray remains useful as it is easy, inexpensive, has low radiation exposure, and is universally available 1
• Normal chest radiographs are reported in 11-62% of diaphragmatic injuries or uncomplicated diaphragmatic hernias, making a negative X-ray insufficient to rule out the diagnosis 1, 2
• Chest X-ray has a sensitivity of only 2-60% for diagnosing left-sided hernias and 17-33% for right-sided hernias 1, 2

CT Scan: The Gold Standard

• In cases of persistent clinical suspicion after chest X-ray, CT scan should be performed to confirm or refute the diagnosis 1
• CT scan is more accurate than chest X-ray in determining the presence, location, and size of the diaphragmatic defect 1
• Contrast-enhanced CT of both chest and abdomen is strongly recommended for stable trauma patients with suspected diaphragmatic hernia 1
• CT can evaluate intrathoracic complications of herniated abdominal organs 1, 3

Key CT Findings in Diaphragmatic Hernia

• Diaphragmatic discontinuity 1, 4
• Segmental non-recognition of the diaphragm 1, 4
• "Dangling diaphragm" sign (visualization of the free edge of the ruptured diaphragm curling toward the center of the abdomen away from the chest wall) 1, 2
• "Dependent viscera" sign (no space between the liver, bowel or stomach and the chest wall) 1, 4
• "Collar sign" (constriction of the herniating abdominal organ at the level of the rupture) 1, 4
• Intrathoracic herniation of abdominal contents 1, 5
• Other findings: elevated abdominal organs, thickened diaphragm, thoracic fluid, abutting intra-abdominal viscera, hypo-attenuated hemidiaphragm, and associated fractured ribs 1, 4

Special Populations and Considerations

• In pregnant patients with suspected non-traumatic diaphragmatic hernia, ultrasonography is suggested as the first diagnostic study 1, 2
• In stable pregnant patients with suspected non-traumatic diaphragmatic hernia, MRI is suggested after ultrasonography 1, 2
• For stable trauma patients with lower chest penetrating wounds and suspected diaphragmatic hernia, diagnostic laparoscopy is recommended 1
• Endoscopy is not recommended in traumatic hernias 1

Limitations and Pitfalls

• CT scan may miss small tears of penetrating injuries like stab wounds when no hernia has yet occurred 1
• Chest X-ray can be normal in intermittent herniation, leading to false negatives 1, 2
• Radiographic findings can be misinterpreted in around 25% of cases 1, 2
• Multislice CT with coronal and sagittal reformatted images provides the most comprehensive evaluation 3, 5

Imaging for Complications

• CT scan can identify signs of ischemia including forward displacement of the gastric bubble, missing gastric folds, absence of gastric wall contrast enhancement, intestinal wall thickening with target enhancement, spontaneous hyper-density of the intestinal wall, lack of enhancement after contrast injection, and parietal pneumatosis with portal and mesenteric venous gas 1
• MRI may be performed in selected patients, particularly in late-presenting cases or when diagnosis remains in doubt 3, 5