Iliohypogastric and ilioinguinal nerves !

The iliohypogastric and ilioinguinal nerves come from L1 and curve around the abdominal wall; they supply the lower abdomen and groin.

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What it is

Two nerves from L1 that run around the abdominal wall above the iliac crest.

What it does

Supply the lower abdominal muscles and feeling in the lower abdomen and groin.

Key facts

Roots: L1 (iliohypogastric often with T12); emerge from the lateral border of psoas major, cross quadratus lumborum
Moves: Lowest fibres of internal oblique and transversus abdominis
Feeling from: Iliohypogastric: suprapubic and lateral gluteal skin; ilioinguinal: upper medial thigh, root of penis or mons, anterior scrotum or labium majus

Relations

Course: Leave the lateral border of psoas, cross the front of quadratus lumborum, pierce transversus abdominis near the iliac crest and run forward between it and internal oblique; the iliohypogastric ends above the superficial ring, the ilioinguinal runs in the inguinal canal
In front: In the posterior abdomen, the lower pole of the kidney and the colon
Behind: The quadratus lumborum

How to find it

On ultrasound, a probe placed just medial to the ASIS on the line toward the umbilicus shows the three muscle layers over the iliac bone; the two nerves are small dots between internal oblique and transversus abdominis, near the deep circumflex iliac artery.

Examination

Tenderness or tapping just medial to the ASIS that reproduces groin pain suggests entrapment; relief after a diagnostic local anaesthetic block supports it

On imaging

Seen with high-frequency ultrasound just above and medial to the ASIS, as two small oval structures between the internal oblique and transversus abdominis; colour Doppler shows the deep circumflex iliac artery beside them. This is the view for the ilioinguinal–iliohypogastric block. They are not seen on CT or MRI; in pain after hernia repair, imaging looks for recurrence or mesh problems.

Clinical notes

Ilioinguinal-iliohypogastric block is used for pain after groin surgery, including hernia repair and orchidopexy in children
Pfannenstiel incision: extending it beyond the lateral edges of the rectus muscles cuts or traps the nerves, causing burning suprapubic and groin pain months later
In open hernia repair the ilioinguinal nerve lies on the cord in the canal and can be caught in sutures or mesh, so it is identified and protected
Lateral laparoscopic ports and iliac crest bone graft harvest can injure the iliohypogastric nerve and its lateral cutaneous branch

Anatomical variants

The ilioinguinal nerve arises from L1 alone in about two-thirds of people, otherwise from T12–L1, L1–L2 or L2–L3
The two may share a common trunk, or one may be missing, its skin territory taken over by the other or by the genitofemoral nerve

Test yourself

Think of the answer, then tap the question to see it.

Between which muscles do the iliohypogastric and ilioinguinal nerves run above the iliac crest?

Between transversus abdominis and the internal oblique; near the ASIS this plane is used for the ultrasound-guided block.

How does the ilioinguinal nerve enter and leave the inguinal canal?

It enters from the side, not through the deep ring, and leaves through the superficial ring in front of the spermatic cord or round ligament.

Which operations most often injure the iliohypogastric and ilioinguinal nerves?

Open inguinal hernia repair and Pfannenstiel incisions extended beyond the rectus edges, causing chronic groin pain or numbness.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): nervus iliohypogastricus; nervus ilioinguinalis TA2 6496
Official Spanish (DeCS): Nervios iliohipogástrico e ilioinguinal
English (TA2): Iliohypogastric and ilioinguinal nerves
Also called: nervus iliopubicus · iliopubic nerve

Sources: Terminologia Anatomica (TA2); Anatomy, Abdomen and Pelvis, Posterior Abdominal Wall Nerves.

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Representative model, for educational purposes only.

Iliohypogastric and ilioinguinal nerves highlighted on the Durgical 3D model