The lateral arcuate ligament is a thickening of the thoracolumbar fascia arching over the quadratus lumborum muscle from the tip of the 12th rib to the transverse process of L1. It provides the origin for the posterolateral fibres of the diaphragm. A Bochdalek hernia passes through a defect in the posterolateral diaphragm at or near the lateral arcuate ligament level.
Forms the posterior lateral diaphragmatic origin over the quadratus lumborum, allowing the posterolateral diaphragm to span the gap between the rib and the transverse process while remaining functionally continuous.
The lateral arcuate ligament site is where Bochdalek hernias occur, most commonly on the left side (right-sided hernias are protected by the liver). Congenital Bochdalek hernia presents in neonates with respiratory distress from bowel in the thorax compressing the developing lung (pulmonary hypoplasia). In adults, Bochdalek hernias are incidental CT findings unless symptomatic. The lateral arcuate ligament is released during laparoscopic lumbar sympathectomy and retroperitoneal approaches to the aorta.
Failure of the posterolateral diaphragm to close during fetal development leaves a foramen at the lateral arcuate ligament site through which bowel herniates into the thorax, compressing the developing ipsilateral lung and causing pulmonary hypoplasia; neonates present with respiratory distress at birth requiring emergency surgical repair and prolonged respiratory support.
