The least splanchnic nerves are paired structures on either side of the spinal column. They are formed from:
- preganglionic sympathetic fibres of spinal segments T11 and T12 which pass through the eleventh and twelfth ganglia of the sympathetic trunk without synapsing
- afferent fibres from abdominal viscera
Beyond the ganglia, the nerves descend in the posteroinferior part of the thorax to pierce the diaphragm through the crura at the level of L1. Within the abdomen, the least splanchnic nerves synapse with postganglionic fibres within the renal ganglion, a subdivision of the coeliac ganglion around the renal artery.