Diaphragmatic hernia results from a failure of the diaphragm to close, allowing abdominal contents to herniate into the chest. Which side is more commonly affected?

• A. Left
• B. Right
• C. Bilateral
• D. No side predominance

Answer: (A)

When diaphragmatic hernias occur, the most common form is a posterolateral Bochdalek defect that results from failure of the pleuroperitoneal membranes to fuse during development. The right side is less often affected because the liver sits under the right hemidiaphragm, providing a protective barrier and aiding earlier closure on that side. Without that large organ on the left, the left posterolateral region is more prone to a failed closure, allowing abdominal contents to herniate into the chest. So, left-sided diaphragmatic hernias are far more common than right-sided, with bilateral or no predominance being much less typical.