Characteristics

• Congenital anomaly with defective fusion of the posterolateral pleuroperitoneal layers.

• 85–90% on the left, 10–15% on the right. Usually unilateral lying posteriorly within the chest.

• Hernia may contain fat or intra-abdominal organs.

• In neonates the hernia may be large and present in utero. This is associated with high mortality secondary to pulmonary hypoplasia (60%).

• Small hernias are often asymptomatic containing a small amount of fat only. They have a reported incidence up to 6% in adults.

Clinical features

• Large hernias are diagnosed antenatally with US.

• Neonates may present with respiratory distress early in life. Early corrective surgery is recommended.

• Smaller hernias are usually asymptomatic with incidental diagnosis made on a routine CXR.

• Occasionally solid organs can be trapped within the chest compromising the vascular supply. Patients report localised pains and associated organ-related symptoms, e.g. change in bowel habit.

Radiological features

• CXR – a well-defined, dome-shaped soft tissue opacity is seen midway between the spine and the lateral chest wall. This may ‘come and go’. There may be loops of bowel or gas-filled stomach within the area. The ipsilateral lung may be smaller with crowding of the bronchovascular markings and occasionally mediastinal shift. An NG tube may lie curled in the chest.

• CT – small hernia are difficult to demonstrate even on CT. Careful inspection for a fatty or soft tissue mass breaching the normal smooth contour of the posterior diaphragm.

Differential diagnosis

• In neonates, both congenital cystic adenomatoid malformation (CCAM) and pulmonary sequestration may have similar features. Cross-sectional imaging with CT ± MRI utilising 2D reformats is often very helpful.

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