What are the clinical and imaging findings of a Bochdalek hernia?

Bochdalek Hernia: Clinical and Imaging Presentation

Bochdalek hernias are congenital posterolateral diaphragmatic defects that typically occur on the left side (80%) and are increasingly detected as incidental findings in asymptomatic adults on CT imaging. 1

Anatomic Location and Laterality

• Bochdalek hernias occur in the posterolateral region of the diaphragm, representing incomplete closure during the eighth week of gestation 1, 2
• Left-sided hernias predominate in 80% of cases, though right-sided and bilateral presentations occur 1, 2
• Right-sided hernias are less common (12-40% of cases) due to the protective effect of the liver 3
• Bilateral hernias account for approximately 1-9% of cases and should be graded one level higher on injury scales 4

Clinical Presentation

Asymptomatic Adults (Most Common)

• Most adult Bochdalek hernias are discovered incidentally during imaging for unrelated conditions 2, 5
• Patients remain asymptomatic despite herniation of abdominal contents into the thorax 2, 5
• The increasing detection rate is directly attributable to widespread use of advanced imaging techniques 2

Symptomatic Presentations

When symptoms occur, patients may present with:

• Dyspnea (86% of symptomatic cases) and orthopnea 3, 4
• Abdominal pain (17%) or non-specific gastrointestinal symptoms 3, 6
• Recurrent pneumonia or respiratory distress 3, 7
• Upper gastrointestinal bleeding from ischemic gastric mucosa 6
• Bowel sounds audible in the chest indicate visceral herniation requiring urgent evaluation 8

Imaging Findings

Chest X-Ray (Initial Screening)

• Chest X-ray can miss up to 62% of diaphragmatic pathology, making it an imperfect screening tool 8
• May show hemidiaphragm elevation >2.5 cm 3
• Findings can be misinterpreted in 25% of cases, sometimes mimicking pneumothorax 3, 9
• Both anteroposterior and lateral views are recommended 4

CT Scan (Gold Standard)

• CT with contrast is the gold standard for diagnosis, with 82% sensitivity and 87% specificity 8, 4
• Key diagnostic CT findings include:
  • Diaphragmatic discontinuity 8, 4
  • "Collar sign" (constriction of herniated viscera at the defect) 8, 4
  • "Dependent viscera sign" 4
  • "Dangling diaphragm" sign 4
• Multislice CT with coronal and sagittal reconstruction should be considered the standard diagnostic method 2
• CT accurately identifies herniated contents (omentum, stomach, colon, spleen, kidney, pancreatic tail) 2, 5

MRI

• MRI in T1 sequences is highly valuable for evaluating fat-containing chest lesions 2
• Recommended as first-line imaging in pregnant patients with suspected non-traumatic diaphragmatic hernias 4

Fluoroscopy

• Fluoroscopy distinguishes paralysis from eventration by assessing for paradoxical motion 8, 3
• In paralysis, the diaphragm moves cephalad during inspiration instead of caudally 3
• Eventration shows no paradoxical motion 3

Herniated Contents

Common herniated structures include:

• Omental fat (most common in incidental findings) 2
• Stomach, transverse colon, and spleen (left-sided hernias) 6, 5, 9
• Tail of pancreas 5
• Right kidney may be adjacent to right-sided defects but typically remains intra-abdominal 2

Critical Diagnostic Pitfalls

• Right-sided diaphragmatic injuries have a 50% delayed diagnosis rate, often presenting later with complications 8, 3
• Delayed diagnosis occurs in 5-45% of all cases 8
• Initial misdiagnosis as bronchitis, pneumonia, or pneumothorax can delay appropriate treatment for months to years 7, 9
• Acute onset dyspnea with mediastinal shift or signs of bowel ischemia represents a surgical emergency requiring immediate intervention 8, 3

High-Risk Features Requiring Urgent Evaluation

• Bowel sounds in the chest with acute abdominal pain and respiratory distress indicate potential strangulation 8
• CT evidence of bowel ischemia or visceral herniation with vascular compromise 3
• Acute respiratory failure from lung compression or cardiac tamponade 1