Do you recommend a CT scan with or without contrast when assessing for a hernia?

CT Scan for Hernia Assessment: With or Without Contrast?

For hernia assessment, CT scan with IV contrast is recommended as it provides superior visualization of herniated structures and potential complications.

Diagnostic Approach for Hernias

Initial Imaging

• For suspected diaphragmatic hernia with respiratory symptoms, a chest X-ray (anteroposterior and lateral) is recommended as the first diagnostic study 1
• When clinical suspicion persists despite normal or equivocal chest X-ray findings, CT scan should be performed to confirm or refute the diagnosis 1

CT Protocol Recommendations

• CT scan with IV contrast enhancement is the gold standard for diagnosing diaphragmatic hernias, with sensitivity and specificity of 14-82% and 87%, respectively 1
• When assessing for any type of hernia, CT with IV contrast provides superior visualization of:
  • Diaphragmatic discontinuity and segmental non-recognition of the diaphragm 1
  • Herniated abdominal contents and their vascular status 1
  • "Collar sign" (constriction of the herniating abdominal organ at the level of the rupture) 1
  • Potential complications such as ischemia, which appears as absence of gastric wall contrast enhancement, intestinal wall thickening, and other vascular abnormalities 1

Why Contrast is Superior

• CT with IV contrast allows assessment of nodular wall thickening and soft tissue attenuation that may indicate complications 1
• Without IV contrast, pathological processes can only be inferred by associated findings such as wall thickening, which may not be present in mild cases 1
• IV contrast helps identify potential ischemic complications through assessment of blood flow to herniated structures 2
• When gastric or intestinal structures are involved in the hernia, neutral oral contrast (water or dilute barium suspension) may also be helpful to delineate the intraluminal space 1

Special Considerations

Trauma Cases

• In stable trauma patients with suspected diaphragmatic hernia, CT scan with contrast enhancement of the chest and abdomen is strongly recommended (Level 1B evidence) 1
• For lower chest penetrating wounds with suspected diaphragmatic hernia, diagnostic laparoscopy may be preferred over imaging 1

Pregnant Patients

• In pregnant patients with suspected non-traumatic diaphragmatic hernia, ultrasonography is suggested as the first diagnostic study, followed by MRI if needed 1
• CT should be avoided in pregnant patients unless absolutely necessary due to radiation exposure 1

Common Pitfalls

• Small tears from penetrating injuries may be missed on CT when no hernia has yet occurred 1
• Intermittent herniation may appear normal on chest X-ray but can still be detected on CT 1
• Gastric underdistension during CT may limit visualization of herniated stomach, requiring careful technique 1

By using CT with IV contrast for hernia assessment, clinicians can achieve the most accurate diagnosis, which facilitates appropriate surgical planning and improves patient outcomes by identifying potential complications that require urgent intervention.