Bochdalek hernia, also known as pleuroperitoneal hernia, is the most common type of congenital diaphragmatic hernia and is located posterolaterally. Large hernias are symptomatic in neonates due to impairment of lung development. Small asymptomatic hernias are typically an incidental CT finding in adults. For neonatal presentation please refer to the article on congenital diaphragmatic hernia.
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Epidemiology
The incidence of congenital diaphragmatic hernia is approximately 2.3 cases in 10,000 live births 5 and Bochdalek hernias account for about 95%. The occurrence is sporadic although other congenital abnormalities may be present. Small Bochdalek hernias in adults may be acquired; they are rare in those <40 years old but increase in incidence up to 35% after age 70 years 6-8.
Diagnosis
Large hernias allow herniation of abdominal contents into the thoracic cavity and may be diagnosed on prenatal ultrasound or postnatal chest radiography. Small hernias are typically seen in adults as incidental findings on CT scan.
Clinical presentation
Large hernias typically present in infancy and about 85% are left-sided. The left opening of the posterior diaphragm closes later in foetal life than the right and the liver may occlude a right-sided opening. Complications in neonates are due to pulmonary hypoplasia.
In adults, incidentally-discovered posterolateral diaphragmatic hernias are present in 0.17% of patients on CT. Of these, right-sided hernias are more common (68%). The great majority are small, with only 27% containing abdominal organs such as bowel, spleen, kidney or liver.
Pathology
Bochdalek hernias are due to failure of closure of the pleuroperitoneal folds in utero. Retroperitoneal and intraperitoneal structures may prolapse through the defect depending on the size of the defect. Pulmonary hypoplasia and neonatal respiratory distress depend on the size of the hernia and the timing of herniation.
Radiographic features
Plain radiograph
On conventional radiographs, the hernia may appear as a posterior soft-tissue opacity on lateral images.
CT
CT demonstrates the diaphragmatic defect and hernial contents: fat and/or abdominal organs. Coronal and sagittal reformatted images show the defect to best advantage.
History and etymology
Vincent Alexander Bochdalek (1801-1883) was a Czech anatomist and pathologist 4.
Differential diagnosis
Bochdalek herniae may mimic diaphragmatic rupture from trauma, but one would expect to find other supportive signs of chest and/or abdominal trauma
Practical points
BBBBB is a simple mnemonic to recall the features of Bochdalek hernias.
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