The iliohypogastric 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, and 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
The iliohypogastric arises from the anterior ramus of the L1 root of lumbar plexus, along with the ilioinguinal nerve.
Upon reaching the anterior abdominal wall, the iliohypogastric nerve enters the transversus abdominis muscle posteriorly at a level just above the iliac crest. By then, the iliohypogastric nerve runs 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: anterior cutaneous and lateral cutaneous branch.
Anterior cutaneous branch
The anterior cutaneous branch continues to run between the internal abdominal oblique and transversus abdominis muscles, innervating both. It runs through the internal oblique muscle about 2 cm medial to the anterior superior iliac spine, then passes through the aponeurosis of the external abdominal oblique muscle about 3 cm superior to the superficial inguinal ring before being distributed to the abdominal skin superior to the pubic area.
Lateral cutaneous branch
The lateral cutaneous branch runs through both the internal and external abdominal oblique muscles at a level superior to the iliac crest and posterior to the iliac branch of T12. It is then distributed to the posterior and lateral aspects of the gluteal skin.
The nerve supplies sensory fibers to the external abdominal oblique, transversus abdominis and internal abdominal oblique 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 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.