What imaging modalities are used for the diagnosis of hernias?

Imaging Modalities for Diagnosis of Hernias

CT scan is the gold standard for diagnosing diaphragmatic hernias with a sensitivity and specificity of 14-82% and 87%, respectively, while ultrasound is the preferred initial imaging modality for inguinal hernias due to its high sensitivity and specificity when performed by experienced operators. 1, 2

Diaphragmatic Hernias

Initial Diagnostic Approach

• In patients without trauma history presenting with respiratory symptoms, chest X-ray (both anteroposterior and lateral views) is recommended as the first diagnostic study 1
• Chest X-ray has a sensitivity of 2-60% for left-sided hernias and 17-33% for right-sided hernias 1
• Normal chest radiographs are reported in 11-62% of diaphragmatic injuries or uncomplicated diaphragmatic hernias 1

CT Scan for Diaphragmatic Hernias

• CT scan is the gold standard for diagnosing diaphragmatic hernias 1
• For stable trauma patients with suspected diaphragmatic hernia, contrast-enhanced CT of chest and abdomen is strongly recommended 1
• Key CT findings include:
  • Diaphragmatic discontinuity
  • "Dangling diaphragm" sign
  • "Dependent viscera" sign
  • "Collar sign" (constriction of herniating organ)
  • Intrathoracic herniation of abdominal contents 1

Special Populations

• In pregnant patients with suspected non-traumatic diaphragmatic hernia:
  • Ultrasonography is suggested as the first diagnostic study 1
  • MRI is recommended after ultrasonography 1

Diagnostic Laparoscopy

• In 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

Inguinal and Other External Hernias

Ultrasound

• Ultrasound is the preferred initial imaging modality for inguinal hernias 3, 2
• Particularly useful in:
  • Women (where physical examination is less reliable)
  • Suspected recurrent hernias
  • Evaluation of surgical complications after repair
  • Differentiating hernias from other causes of groin pain 3
• Point-of-care ultrasound (POCUS) is useful for evaluating gallbladder pathology, acute appendicitis, free fluid, or intestinal distention in patients with suspected hernias 1

MRI for Inguinal Hernias

• MRI has higher sensitivity and specificity than ultrasound 3
• Particularly useful for diagnosing occult hernias when clinical suspicion is high despite negative ultrasound findings 3

CT for Abdominal Wall Hernias

• CT is valuable when patients are obese or have had previous surgery 4
• Helps distinguish hernias from masses of the abdominal wall (tumors, hematomas, abscesses) 4
• Particularly useful for internal hernias, showing:
  • Small bowel obstruction
  • Saclike mass or cluster of dilated small bowel loops at abnormal anatomic locations
  • Engorged, stretched, and displaced mesenteric vascular pedicle 5

Specialized Imaging for Specific Hernia Types

Hiatal Hernias

• Fluoroscopic studies are most useful:
  • Biphasic esophagram
  • Single-contrast esophagram
  • Upper GI series 1
• These studies provide anatomic and functional information on:
  • Esophageal length
  • Esophageal stricture
  • Presence of gastroesophageal reflux
  • Reflux esophagitis 1

Post-Bariatric Surgery Hernias

• Contrast-enhanced CT with oral contrast administration is the study of choice 1
• Administration of oral and IV contrast is fundamental to identify landmarks 1
• After laparoscopic Roux-en-Y gastric bypass (LRYGB), CT is important for detecting:
  • Internal hernias (with 87.1% specificity)
  • Small-bowel obstruction
  • Anastomotic stenosis
  • Perforation 1

Common Pitfalls and Caveats

• Normal chest X-rays do not exclude diaphragmatic hernias (false negatives in 11-62% of cases) 1
• CT may miss small tears from penetrating injuries like stab wounds when no hernia has yet occurred 1
• A negative CT scan should not rule out internal hernias in post-bariatric surgery patients 1
• Ultrasound accuracy for hernia diagnosis is highly dependent on the operator's expertise 2
• In pregnant women, ultrasound and MRI are preferred to limit radiation exposure 1
• Herniography (injecting contrast media into the hernial sac) may be used in selected patients with suspected inguinal hernias 3