The superior hypogastic plexus arises from pre- and post-ganglionic sympathetic fibers arising from the pre-aortic plexus in the region of the inferior mesteric artery (inferior mesenteric plexus). These fibers arise from lower intermediolateral cell column of L1-L3.

The superior hypogastric plexus lies immediately deep to the parietal peritoneal at the L5/S1 level in front of the left common iliac vein. It gives rise to right and left hypogastric nerves which descend on the posterolateral pelvic wall just underneath the parietal endopelvic fascia of the rectum.

The hypogastric nerves give rise to the inferior hypogastric plexus. The inferior hypogastric plexus is a rhomboid-shaped flat plexus of nerves lying beneath the parietal layer of endopelvic fascia lateral to the mid rectum.

The inferior hypogastric plexus is joined by parasympathetic fibers from S2-S4 nerves (Nervi erigentes) to form the pelvic plexus of nerves.

Fibers from the pelvic plexus project forward and medially to the pelvic viscera (bladder, rectum, seminal vesicles, erectile tissue of corpus cavernosa, uterus and vagina).

Possible sites of injury during surgery include:

• With high dissection and ligation of IMA the pre-aortic sympathetic fibers may be damaged.
• The superior hypogastric plexus may be damaged with mobilization of the sigmoid mesocolon.
• The hypogastic nerves are vunerable to diathermy injury during initial posterior rectal mobilization as the peritoneum is breached (below which they reside, often just outside the mesorectal plane, 1-2cm medial to ureter.

Damage to the above exclusively SNS structures may lead to ejaculatory failure or retrograde ejaculation.

• The inferior hypogastic plexus and pelvic splanchnic nerves can be damaged with rectal mobilization if the mesorectal plane is not respected and the dissection continues posterior or lateral to the parietal endopelvic fascia.
• The terminal branches of the pelvic plexus (cavernous nerves close to the posterolateral margin of prostate and lateral margins of Denonvillier’s fascia) may be damaged as the anterior rectum is dissected from the semial vesicles.

Damage to the pelvic plexus, or mixed PNS and SNS nerves may lead to erectile impotence, urinary retention or both.

In the informed consent process the patient needs to be made aware that these structures may be damaged inadvertently or sacrificed intentionally in an attempt to achieve R0 resection.