The lesser splanchnic nerves are paired structures on either side of the vertebral column. They are formed from preganglionic sympathetic nerve fibres which pass through the ninth and tenth paravertebral ganglia on each side without synapsing. Also, they carry afferent fibres.
The fibres converge to form the lesser splanchnic nerves which pass inferiorly from thorax to abdomen lateral to the spinal column on each side. They pass slightly lateral to the greater splanchnic nerves during their descent through the posterior mediastinum. They pierce the diaphragm through the crura at the level of L1. Within the abdomen, they synapse in the coeliac ganglia around the aorta.