The iliohypogastric nerve (not to be confused with the hypogastric nerve) is a mixed branch of the lumbar plexus. It arises as a single trunk along with the ilioinguinal nerve from the anterior/ventral ramus of the L1 spinal nerve root. The nerve starts its course on the posterior abdominal wall, emerging from the upper border of the psoas major muscle. It then crosses obliquely to the anterior abdominal wall, running between the anterior abdominal muscles.
Being a mixed nerve, the iliohypogastric nerve supplies both motor and sensory innervation to the abdominal muscles, as well as sensory innervation to the skin of the posterolateral gluteal and suprapubic regions.
This article will describe the anatomy and function of the iliohypogastric nerve, as well as some clinical notes.
|Origin||Lumbar plexus (L1)|
|Branches||Anterior cutaneous branch, lateral cutaneous branch|
Motor: Transversus abdominis, internal abdominal oblique, conjoint tendon.
Sensory: External abdominal oblique, transversus abdominis, internal abdominal oblique; Skin of the suprapubic region and posterolateral aspect of gluteal region.
- Clinical notes: Iliohypogastric nerve damage
After it emerges from the upper lateral border of the psoas major muscle, the iliohypogastric nerve passes inferolaterally, posterior to the lower pole of the kidneys and in front of the quadratus lumborum muscle.
As it runs toward the anterior abdominal wall, the iliohypogastric nerve pierces the transversus abdominis muscle posteriorly, just above the iliac crest and continues anteriorly between the transversus abdominis and the internal abdominal oblique muscles.
Whilst passing between the transversus abdominis and internal abdominal oblique, the iliohypogastric nerve gives off two branches: lateral cutaneous and anterior cutaneous branch.
Lateral cutaneous branch
The lateral cutaneous branch pierces both the internal and external abdominal oblique muscles superior to the iliac crest to supply the posterolateral aspects of the gluteal skin.
Anterior cutaneous branch
The anterior cutaneous branch continues anteriorly between the internal abdominal oblique and transversus abdominis muscles, innervating both muscles. It pierces the internal oblique muscle about 2 cm medial to the anterior superior iliac spine. This branch then passes through the aponeurosis of the external abdominal oblique muscle about 3 cm above the superficial inguinal ring to supply the skin superior to the pubic area.
The nerve supplies sensory fibers to the the external abdominal oblique, internal abdominal oblique and transversus abdominis muscles. The iliohypogastric also supplies the skin of the suprapubic region and the posterolateral aspect of the gluteal region.
The iliohypogastric nerve also supplies motor fibers to the transversus abdominis and the internal abdominal oblique muscles. It also innervates the conjoint tendon, a tendon formed from the common aponeurosis of the transversus abdominis and internal oblique muscles.
Clinical notes: Iliohypogastric nerve damage
Damage to the iliohypogastric nerve is rarely isolated and other nerves may be affected. Injury can occasionally occur during surgery with an oblique open approach to the appendix. Damage to the iliohypogastric nerve can also occur in transverse incisions of the lower abdomen, during a hysterectomy, for example. A noticeable sensory loss is rare, as the suprapubic skin receives innervation from multiple nerves.
Injuries to the nerve can occur due to:
- A direct surgical trauma or due to entrapment of the nerve in scar tissue following the surgical procedure.
- Injuries in sport, such as muscle tearing or trauma, can also damage the nerve.
- Damage to the nerve can also rarely occur in pregnancy due to a rapid expansion of the abdomen that occurs in the third trimester. This is referred to as idiopathic iliohypogastric syndrome.
Trauma or entrapment of the iliohypogastric nerve can cause a burning pain in the suprapubic and inguinal regions. Treatment is with a local anesthetic injection, pain-relieving medications such as anti-inflammatories or with physical therapy such as cryotherapy.
Division of the iliohypogastric nerve above the level of the anterior superior iliac spine can cause weakening of the inguinal canal’s posterior wall. This can predispose to direct hernia formation.
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