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Iliohypogastric nerve

The iliohypogastric nerve is a mixed sensory and motor nerve, one of the upper branches of the lumbar plexus. It arises mainly from the anterior ramus of the L1 spinal nerve, with occasional contributions from T12. It courses obliquely across the abdominal wall, supplying both muscular and cutaneous branches.

It is clinically important in abdominal wall surgery, hernia repair, and as a source of chronic groin pain when injured or entrapped.

Synonyms

  • Nervus iliohypogastricus

  • L1 upper lumbar plexus branch

  • Superior ilioinguinal nerve (historical usage)

Origin, Course, and Branches

  • Origin:

    • Arises from the anterior ramus of L1, sometimes with contribution from T12

  • Course:

    • Emerges from the lateral border of the psoas major muscle

    • Crosses anterior to the quadratus lumborum muscle

    • Pierces the transversus abdominis near the iliac crest

    • Runs between transversus abdominis and internal oblique muscles

    • Divides into terminal branches before the rectus sheath

  • Branches:

    • Lateral cutaneous branch: Supplies skin over the superolateral gluteal region

    • Anterior cutaneous branch: Supplies skin over the hypogastric (pubic) region

    • Muscular branches: To transversus abdominis and internal oblique muscles

Relations

  • Anteriorly: Abdominal wall muscles (transversus abdominis, internal oblique)

  • Posteriorly: Quadratus lumborum muscle

  • Superiorly: 12th rib and subcostal nerve

  • Inferiorly: Ilioinguinal nerve (closely related course)

  • Laterally: Iliac crest

Function

  • Motor: Supplies fibers to the internal oblique and transversus abdominis muscles

  • Sensory: Provides sensation to the skin of the lateral gluteal region and suprapubic area

  • Plays a role in maintaining abdominal wall integrity and sensory feedback

Clinical Significance

  • May be injured during appendectomy, Pfannenstiel incision, hernia repair, or laparoscopic port placement

  • Injury causes loss of sensation in suprapubic skin and weakness of abdominal wall

  • Entrapment leads to iliohypogastric neuralgia (pain radiating to lower abdomen and groin)

  • Target for nerve blocks in abdominal surgery and chronic pain management

MRI Appearance

T1-weighted images:

  • Appears as a thin, linear low-to-intermediate signal structure within bright fat planes

T2-weighted images:

  • Shows intermediate to mildly hyperintense signal relative to muscle

  • Pathology (edema, inflammation) increases brightness

STIR (Short Tau Inversion Recovery):

  • Normal nerve is low signal

  • Inflamed or injured nerve becomes bright hyperintense

T1 Fat-Sat Post-Contrast:

  • Minimal or no enhancement in normal state

  • Pathological nerve shows focal or diffuse enhancement (neuritis, tumor infiltration)

3D T2 SPACE / CISS:

  • Nerve shows intermediate to mildly hyperintense signal compared to muscle

  • Surrounded by bright fat and peritoneal fluid, giving excellent contrast

  • Very effective for tracing the course of the nerve and detecting entrapment or small lesions

CT Appearance

Non-Contrast CT:

  • Not directly visualized; course inferred as a thin structure within abdominal wall fat planes

  • Surrounding fat enhances visibility of the expected nerve pathway

Post-Contrast CT:

  • Normal nerve does not enhance significantly

  • Pathology (inflammatory infiltration, tumor spread) may appear as focal thickening or enhancing nodules along its course

MRI image

Iliohypogastric nerve 1

MRI image

Iliohypogastric nerve MRI coronal image