The pelvic portion of each sympathetic trunk is situated in front of the sacrum, medial to the anterior sacral foramina.
It consists of four or five small sacral ganglia, connected together by interganglionic cords, and continuous above with the abdominal portion.
Below, the two pelvic sympathetic trunks converge, and end on the front of the coccyx in a small ganglion, the ganglion impar, also known as azygos [1] or ganglion of Walther.
This ganglion plays a crucial role in patients experiencing pain in the pelvic and perineal structures, as it provides both nociceptive and sympathetic supply to these regions.
[2] This article incorporates text in the public domain from page 984 of the 20th edition of Gray's Anatomy (1918)