What imaging study is recommended to evaluate a hernia?

Imaging for Hernia Evaluation

For most hernias, contrast-enhanced CT of the abdomen with both IV and oral contrast is the gold standard imaging modality, providing superior diagnostic accuracy for internal hernias, post-surgical hernias, and complicated cases. 1

Imaging Selection by Hernia Type

Inguinal and External Abdominal Wall Hernias

• Point-of-care ultrasound (POCUS) is the first-line imaging study for suspected inguinal and external hernias, offering real-time dynamic assessment without radiation exposure 1
• CT scan should be ordered when ultrasound results are equivocal or when complications such as bowel obstruction are suspected 2
• In obese patients or those with previous groin surgery, CT is more reliable than ultrasound due to technical limitations 2
• MRI is particularly useful in pregnant patients or those with complex anatomy where radiation exposure is a concern, with high accuracy (sensitivity 94.5%, specificity 96.3%) 2

Diaphragmatic Hernias

• Chest X-ray is the initial diagnostic study in patients without trauma history presenting with respiratory symptoms, though sensitivity is poor (2-60% for left-sided, 17-33% for right-sided hernias) 1
• Contrast-enhanced CT of chest and abdomen is the gold standard for diagnosing diaphragmatic hernias, with key findings including diaphragmatic discontinuity, "dangling diaphragm" sign, "dependent viscera" sign, "collar sign", and intrathoracic herniation of abdominal contents 1
• For stable trauma patients with suspected diaphragmatic hernia, contrast-enhanced CT is strongly recommended 1
• In pregnant patients with suspected non-traumatic diaphragmatic hernia, ultrasonography is the first diagnostic study, followed by MRI if necessary 1

Hiatal Hernias

• Fluoroscopic studies (biphasic esophagram, single-contrast esophagram, or upper GI series) are the most appropriate initial imaging studies for suspected hiatal hernia 1
• These studies detect presence and size of hiatal hernia, provide anatomic and functional information on esophageal length, identify esophageal strictures, and assess for gastroesophageal reflux 1
• Double-contrast upper GI series is particularly beneficial for detecting hiatal hernia and evaluating for reflux esophagitis 1
• For large hiatal hernias, an upper GI series evaluation is recommended for complete assessment of the stomach 1
• CT abdomen with IV contrast may be considered when evaluating the relationship between hernia and cardiac structures, though it is controversial for routine use 1

Post-Bariatric Surgery Hernias and Internal Hernias

• Contrast-enhanced CT with both oral and IV contrast is mandatory for suspected internal hernias, as these are difficult to diagnose clinically and carry high morbidity if missed 1
• Both oral and IV contrast are fundamental to identify anatomical landmarks (gastric pouch, Roux limb, jejuno-jejunal anastomosis, excluded stomach) 1
• CT demonstrates critical findings including clustered/crowded dilated bowel loops, engorged and displaced mesenteric vessels, the "whirlpool sign" (swirled mesenteric vessels), and displacement of adjacent structures 1
• CT has high specificity (87.1%) and negative predictive value (96.8%) for internal hernias post-RYGB 1

Critical Pitfalls to Avoid

False Negatives

• Normal chest X-rays do not exclude diaphragmatic hernias, with false negatives in 11-62% of cases 1
• A negative CT scan should not rule out internal hernias in post-bariatric surgery patients—40-60% of surgically confirmed internal hernias had negative CT scans 1
• Maintain low threshold for diagnostic laparoscopy if clinical suspicion persists despite negative imaging 1

Inappropriate Imaging Selection

• Ordering CT as first-line imaging for hiatal hernia when fluoroscopic studies are more appropriate and informative 1
• Using non-contrast CT when vascular assessment is needed, particularly when evaluating the relationship between the hernia and cardiac structures 1
• If IV or oral contrast is contraindicated (allergy, acute kidney failure), laparoscopic exploration is mandatory due to low sensitivity of non-contrast studies 1

When to Proceed Directly to Surgery

• Acute signs of small bowel obstruction (vomiting, acute abdomen) require immediate diagnostic laparoscopy without waiting for imaging 1
• Persistent abdominal pain in post-bariatric surgery patients warrants early surgical intervention even if stable and CT is negative 1