What is the diagnostic and management approach for eventration of the diaphragm versus diaphragmatic hernia?

Eventration vs Diaphragmatic Hernia: Key Distinctions and Management

Fundamental Anatomic Difference

Eventration of the diaphragm is an abnormal elevation of intact but thinned/weakened diaphragmatic muscle with preserved attachments to the chest wall, while diaphragmatic hernia involves an actual defect or discontinuity in the diaphragm allowing herniation of abdominal contents into the thorax. 1, 2

The critical distinction is that eventration maintains diaphragmatic continuity despite abnormal elevation, whereas true hernias have a breach in the diaphragmatic integrity 3, 1.

Diagnostic Approach

Initial Imaging

• Start with chest X-ray (anteroposterior and lateral views) as the first-line diagnostic study for both conditions 4
  • Both conditions show hemidiaphragm elevation on plain films
  • Hernias may demonstrate bowel gas patterns, air-fluid levels, or visible bowel loops in the thorax 4
  • Sensitivity is limited (2-60% for left-sided, 17-33% for right-sided hernias), with normal radiographs in 11-62% of cases 4, 5

Advanced Imaging for Definitive Diagnosis

• CT scan with contrast enhancement of chest and abdomen is the gold standard for diagnosing diaphragmatic hernia 4, 6

  • Sensitivity 14-82%, specificity 87% 4
  • Key CT findings for hernia: diaphragmatic discontinuity, "collar sign" (constriction at defect), "dangling diaphragm" sign, herniated organs abutting chest wall 4

• Ultrasound can differentiate eventration from hernia with specific signs 2

  • For hernia: folding of free muscle edge with narrow angle waist (100% specificity) 2
  • For eventration: broad angle waist with hypoechoic strip of muscle covering the elevated area (100% specificity) 2
  • However, definitive differentiation may not be possible in approximately one-third of patients 2

Common Diagnostic Pitfall

The correct diagnosis between eventration and hernia can often only be made definitively at surgery, as large eventrations can mimic hernias clinically and radiographically 7, 3. This is particularly true when no bowel loops are visible above the diaphragm on imaging 2.

Clinical Presentation Overlap

Both conditions can present with:

• Respiratory distress, tachypnea, dyspnea 3, 1
• Recurrent pneumonia 1
• Feeding difficulties and failure to thrive 3, 1
• Many cases are asymptomatic and discovered incidentally 7, 1

Diaphragmatic hernias carry higher risk of life-threatening complications including bowel obstruction, strangulation, volvulus, and visceral ischemia 4, while eventration typically causes symptoms through lung compression and mediastinal shift 1.

Management Differences

Eventration Management

• Asymptomatic eventration can be managed conservatively with observation 1
• Symptomatic eventration requires diaphragmatic plication 1
  • Plication restores normal diaphragm position and pulmonary volume 1
  • Results in immediate symptom remission in most patients 1
  • Post-operative fluoroscopy shows immobile but non-paradoxical diaphragm 1

Diaphragmatic Hernia Management

• All diaphragmatic hernias require surgical repair due to risk of complications 6
• For stable patients without peritonitis: laparoscopic approach is acceptable 5
• For patients with peritonitis or hemodynamic instability: open abdominal approach is mandatory 5
• Surgical repair involves closing the diaphragmatic defect, not just plication 6

Algorithmic Approach

1. Chest X-ray showing elevated hemidiaphragm → Proceed to advanced imaging 4

2. If ultrasound available and experienced operator:

   • Look for narrow angle waist + folded free edge = hernia 2
   • Look for broad angle waist + muscle covering = eventration 2

3. If diagnosis unclear or hernia suspected: obtain contrast-enhanced CT chest/abdomen 4

   • Diaphragmatic discontinuity = hernia requiring repair 4
   • Intact but elevated diaphragm = eventration 1

4. Symptomatic patients:

   • Hernia → surgical repair urgently if complicated, electively if uncomplicated 5, 6
   • Eventration → plication if conservative management fails 1

5. Asymptomatic patients:

   • Hernia → elective surgical repair (risk of future complications) 6
   • Eventration → observation acceptable 1

Critical caveat: Be prepared for intraoperative diagnosis change, as preoperative imaging may misclassify eventration as hernia in up to 31% of cases 7, 2.