Bochdalek hernia

Figures (7)

Patient history

An elderly lady, widowed for several years and with no children or relatives, was admitted to a retirement home with the first symptoms of dementia. A chest radiograph performed during a routine check showed an abnormality.

Imaging findings — key points

• The chest radiograph shows a large, smooth, rounded opacity in the left lower hemithorax, obscuring the medial aspect of the left hemidiaphragm and containing subtle gas lucencies.
• Multidetector CT in coronal and sagittal planes demonstrates a defect in the posterior aspect of the left hemidiaphragm with herniation of retroperitoneal fat and bowel into the pleural cavity.
• The herniated contents pass through the Bochdalek foramen and show a collar sign at the diaphragmatic defect, with mass effect on the adjacent lung.
• The left kidney remains in a normal position, and there is no pleural effusion or lung mass.
• The lung parenchyma adjacent to the hernia shows compressive atelectasis but no consolidation or nodule.

Discussion

Bochdalek hernia is a congenital posterolateral diaphragmatic defect that usually presents in neonates with respiratory distress, but a minority remain asymptomatic until adulthood, when they are found incidentally or present with abdominal pain, obstruction or strangulation. CT is definitive, showing a defect in the posterior diaphragm with herniation of fat, omentum, bowel, spleen or kidney into the thorax and a collar sign at the neck of the hernia. The main differentials are a lung or pleural mass, a diaphragmatic lipoma and eventration, all of which lack a true defect. Symptomatic or complicated hernias require surgical repair, and even asymptomatic adult cases are often repaired because of the risk of strangulation.

Differential diagnosis

Alternative diagnosis	Key features that distinguish it from this case
Pulmonary or pleural tumour	A lung or pleural tumour is a solid mass that enhances and may invade the chest wall, without a diaphragmatic defect or herniated fat and bowel.
Diaphragmatic lipoma	A diaphragmatic lipoma is a fat-containing mass confined to the diaphragm without a defect or herniation of abdominal contents.
Diaphragmatic eventration	Eventration is a smooth elevation of an intact hemidiaphragm without a focal defect or herniated viscera, and the diaphragm remains continuous.
Pleural effusion or empyema	A loculated effusion is fluid density with pleural enhancement and no connection to the abdominal cavity.

The confirmed diagnosis itself is not included as an alternative — it is stated separately below.

See all Chest differential diagnoses