Separation of the thoracic and abdominal cavities occurs in the eighth week of gestation, when closure of the pleuroperitoneal canal takes place. Failure of this process results in a congenital diaphragmatic hernia. In 1948, Bochdalek described incomplete fusion of the posterolateral diaphragmatic foramina, through which abdominal viscera might herniate. Bochdalek stressed that this hernia may not purely be a congenital malformation, but rather the stretching of a defect existent in almost any fetus, resulting in rupture of an intact membrane of the diaphragm referred to as the trigone of Bochdalek.1,2
Subsequent case reports have predominantly described left sided herniation as being more common, as pleuroperitoneal folds preferentially terminate on the right side during embryonic development. It is also conceivable that the liver confers protection to herniation of abdominal contents.2,3
The incidence of diaphragmatic (Bochdalek) herniation in neonates is 1 in 2000–5000.4
Presentation in adulthood is very uncommon; a PubMed search (Bochdalek, hernia, adult) revealed just over 50 reported symptomatic cases. The true prevalence is difficult to estimate, because hernias are increasingly identified by imaging for non-specific symptoms. The largest study to date estimates 0.17% incidence in adults,5
remarkably similar to that in neonates. Various abdominal organs may migrate through the defect. Colonic herniation is most common and may present with obstruction and strangulation.6–8
Herniations of the stomach, small bowel, spleen, omentum, and kidney have also been described.9
The current case included pancreatic herniation, which has not previously been documented.
Principal symptoms at birth are respiratory distress from pulmonary hypoplasia, because intestinal herniation prevents lung maturation. There may be cyanosis, dyspnoea and lateral displacement of the apex of the heart. In adulthood, however, respiratory symptoms are rare. Upper gastrointestinal symptoms, often unusual (vomiting, dyspepsia, or abdominal pain triggered by increased intra-abdominal pressure) are more common.
Chest radiographs may demonstrate diaphragmatic elevation on the affected side and an air–fluid interface, or soft tissue shadows related to solid viscera. Confirmation by CT scan is appropriate.10
It may be misdiagnosed as a pleural effusion or lung cyst.11
High proportions of cases are asymptomatic, or have symptoms that are difficult to attribute to the herniation; careful consideration should then be given to the potential consequences of intervention.
Definitive treatment means operative repair, with reduction of the herniated organs and repair of the defect. Specialist advice is appropriate, because hepatic herniation necessitates thoracotomy, rather than laparotomy, and a laparoscopic assisted approach in experienced hands may reduce morbidity. Congenital diaphragmatic (Bochdalek) herniation should be considered as a differential diagnosis if an incarcerated hiatal hernia is detected on a chest radiograph or at endoscopy.
- Separation of the thoracic and abdominal cavities via closure of the pleuroperitoneal canal takes place in the eighth week of gestation. Failure of this process results in a Bochdalek’s hernia.
- Left sided herniation is more common.
- Symptomatic Bochdalek’s hernia usually present in childhood with respiratory distress from pulmonary hypoplasia.
- In adulthood, however, respiratory symptoms are rare. Upper gastrointestinal symptoms (vomiting, dyspepsia, or abdominal pain triggered by increased intra-abdominal pressure) are more common.
- Congenital diaphragmatic (Bochdalek) herniation should be considered as a differential diagnosis if an incarcerated hiatal hernia is detected on a chest radiograph or at endoscopy.