Iliohypogastric nerve

The iliohypogastric nerve arises from the anterior ramus of the L1 nerve root of the lumbar plexusalong with the ilioinguinal nerve. It a sensory nerve that provides a lateral and anterior cutaneous branch to supplybranches supplying the posterolateral gluteal skin and skin in the pubic region.

Gross anatomy

Origin

The iliohypogastric nerve arises with the ilioinguinal nerve as a single trunk from the anterior ramus of the L1 nerve root of the lumbar plexus. This trunk enters the abdomen behind the medialarcuate ligament and runs anterolaterally in a course parallel and superior to the iliac crests traversing the anterior surface of the quadratus lumborum muscle. The common trunk is short and the nerve soon divides in to iliohypogastric and ilioinguinal nerves at the lateral edge of the psoas muscle.

Course and branches

After branching from the common trunk with the ilioinguinal nerve, the iliohypogastric nerve continues along the anterior surface of the quadratus lumborum muscle posterior to the kidney.

The nerve pierces the transversus abdominis muscle and continues to travelcoursing anteriorly between the transversus abdominis and internal oblique muscles. Above the iliac crest the iliohypogastric nerve gives a lateral cutaneous branch to supply posterolateral gluteal skin.

The remaining part of the iliohypogastric nerve (the anterior cutaneous branch) continues to travelcourses anteriorly and piercestopierces the internal oblique muscle just above and slightly medial to the anterior superior iliac spine. The nerve then courses before turning obliquely downwards and medially becoming increasingly more superficial as it descends. Just superior to the superficial inguinal ring the anterior branch pierces the aponeurosis of the external oblique to distribute multiple cutaneous branches to the skin of the pubic region.

Branches and Supply

The iliohypogastric nerve gives anterior and lateral cutaneous branches as well as supplying branches to the abdominal musculature during its course.

The lateral cutaneous branch arises from the iliohypogastric nerve above the iliac crest. The branch travels inferiorly and pierces the internal and external oblique muscles to supplysupplies the upper part of the buttock behind the area supplied by the subcostal nerve.

The anterior cutaneous branch is the continuation of the iliohypogastric nerve anteriorly. Just above the ASIS the nerve pierces the internal oblique muscle and continues inferomedially between the external and internal oblique muscles. Approximately 2.5cm above the superficial inguinal ring andthe nerve terminates by supplying skin over the lower part of the rectus abdominis and mons pubis.

Relations

Proximally the iliohypogastric nerve lies on the anterior surface of the quadratus lumborum muscle and posterior to the kidney. The ilioinguinal nerve travels inferiorly to the iliohypogastric nerve and has a more oblique course as it travels to the iliac crest typically traversing the iliacus muscle.

Variant anatomy

The iliohypogastric nerve has been shown to be absent in ~20% of lumbar plexus examined in cadaveric studies. Occasionally it was found that the iliohypogastric and ilioinguinal nerves remained conjoined (within a common epineurium) well after exiting the substance of the psoas major musculature although this variation was quite rare. 

The size of the iliohypogastric nerve is inversely proportional to the size of the ilioinguinal nerve.