Bochdalek hernia (BH) is a defect in the posterolateral diaphragm that allows abdominal contents to migrate into the chest cavity. While this condition is overwhelmingly diagnosed in newborns due to severe respiratory distress, a small number of people reach adulthood with an undiagnosed defect. The rarity of an adult presentation makes understanding the underlying cause and the triggers for becoming symptomatic a frequent point of inquiry. Though the defect is congenital, its clinical manifestation in adults is the result of a secondary event exploiting a pre-existing weakness.
Understanding the Embryonic Origin
The fundamental cause of a Bochdalek hernia is a failure of the diaphragm to fully close during fetal development. This organ forms from multiple structures, including the pleuroperitoneal membranes, which must fuse completely to separate the chest and abdominal cavities. This fusion process typically occurs between the 8th and 10th week of gestation.
If the pleuroperitoneal membranes fail to join, a permanent opening remains in the posterolateral part of the diaphragm, known as the foramen of Bochdalek. Since the left side of the diaphragm closes later than the right, approximately 85% of these congenital defects occur on the left side. The resulting defect is a structural abnormality that creates a potential pathway for abdominal organs to enter the thoracic space.
Why the Defect Remains Hidden
The reason a Bochdalek hernia can go decades without detection is that the structural defect is often quite small, leading to a latent or asymptomatic state. An asymptomatic hernia may only allow minimal tissue, such as retroperitoneal fat or a small portion of the omentum, to protrude into the chest. The pressure dynamics between the abdomen and chest can remain stable enough to prevent the migration of larger organs.
The small opening can be effectively plugged by the surrounding tissue or the minimal contents that have herniated. This temporary occlusion prevents the larger abdominal organs from migrating upward, which would cause noticeable symptoms. Consequently, the defect is often discovered incidentally during imaging for an unrelated issue, even in adulthood.
Specific Factors That Cause Adult Onset
The underlying cause of the defect is congenital, but the onset of symptoms in adulthood is driven by immediate triggers that exploit the existing weakness. These triggers are events that create a sudden or sustained increase in intra-abdominal pressure. This increased pressure forces organs through the small, pre-existing hole, causing the latent defect to become clinically symptomatic.
Specific examples of these pressure-increasing events include blunt abdominal trauma, such as those sustained in motor vehicle accidents or severe falls. Chronic, severe straining from conditions like a persistent cough, chronic constipation, or repeated heavy lifting can also be contributing factors. Furthermore, rapid weight gain, obesity, and pregnancy increase the volume and pressure within the abdominal cavity, providing the force necessary to push contents through the diaphragmatic opening.
Recognizing Symptoms and Treatment Overview
Symptoms of an adult Bochdalek hernia can be vague and often mimic other more common conditions, making diagnosis challenging. Gastrointestinal complaints are the most common presenting symptoms in adults, often including non-specific abdominal pain, recurrent nausea and vomiting, or postprandial fullness. When the herniated organs become obstructed or twisted, the symptoms can escalate quickly to severe pain and signs of a bowel obstruction.
Respiratory symptoms are also common and can manifest as unexplained shortness of breath, chronic chest pain, or recurrent chest infections. These pulmonary and gastrointestinal symptoms frequently worsen following a large meal or during physical exertion, as the abdominal contents press further into the chest cavity. Because the initial chest X-ray can be inconclusive, advanced imaging is often required.
A computed tomography (CT) scan is the most accurate method for diagnosis, as it clearly visualizes the defect and the herniated organs. The definitive treatment for a symptomatic adult Bochdalek hernia is surgical repair to prevent life-threatening complications like organ strangulation. The procedure involves reducing the herniated contents back into the abdomen and closing the diaphragmatic defect.
Surgical approaches are most often performed using minimally invasive techniques, such as laparoscopy or thoracoscopy, with the goal of safely returning the organs to the abdominal cavity and securing the diaphragm. Repair is recommended even for asymptomatic hernias to eliminate the risk of a future, potentially fatal, complication.