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# Iliolumbar vessels

The iliolumbar artery and vein lie near L5 and the inner side of the iliac wing; they supply the psoas, the [iliacus](https://durgical.com/en/anatomy/iliacus-muscle/) and the lower [spine](https://durgical.com/en/anatomy/region/spine/).

Official name: Iliolumbar artery

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## What it is

An artery and vein near the L5 transverse process and the inner side of the iliac wing.

## What it does

Supply the psoas, iliacus, [quadratus lumborum](https://durgical.com/en/anatomy/quadratus-lumborum-muscle/) and lower spine. The vein ties the left common iliac vein to the side wall and is tied before moving it in ALIF.

## Key points

- The iliolumbar vein is the key tether of the left common iliac vein: it is found and tied before that vein is moved to reach L4–L5 from the front or side
- The artery climbs out of the [pelvis](https://durgical.com/en/anatomy/region/pelvis/) behind the psoas major, in front of the lumbosacral trunk and sacroiliac joint, to the L5 transverse process and the iliac fossa
- Its branches join the lowest [lumbar arteries](https://durgical.com/en/anatomy/lumbar-arteries/), forming a collateral path when the aorta or [common iliac arteries](https://durgical.com/en/anatomy/common-iliac-artery/) are blocked

## Key facts

**Origin**
Iliolumbar artery: posterior division of internal iliac artery; iliolumbar vein drains into the internal or common iliac vein

**Branches**
Lumbar branch (psoas, quadratus lumborum, spinal branch at L5–S1) and iliac branch (iliacus, ilium)

**Supplies**
Psoas, quadratus lumborum, iliacus, ilium, lower lumbar canal; iliolumbar vein is a key landmark in anterior L4–L5 exposure

## Relations

**Course**
The artery runs up and out from the [internal iliac artery](https://durgical.com/en/anatomy/internal-iliac-artery/), behind the [obturator nerve](https://durgical.com/en/anatomy/obturator-nerve/) and external iliac vessels and in front of the lumbosacral trunk, then splits near the L5 transverse process into lumbar and iliac branches; the vein follows it down to the internal or [common iliac vein](https://durgical.com/en/anatomy/common-iliac-vein/)

**In front**
Obturator nerve, external iliac vessels and [psoas major](https://durgical.com/en/anatomy/psoas-major/)

**Behind**
Lumbosacral trunk, [sacroiliac joint](https://durgical.com/en/anatomy/sacroiliac-joint/) and [iliolumbar ligament](https://durgical.com/en/anatomy/iliolumbar-ligament/)

**Above**
L5 transverse process and, higher, the lowest lumbar vessels with which it connects

## How to find it

In the left retroperitoneal approach to L4–L5, the vein is found at the lower lateral edge of the left common iliac vein, running back and out into the angle between the L5 body and the psoas major.

## On imaging

Small and best seen on contrast CT or MRI used to plan an anterior or lateral approach to L4–L5: the iliolumbar vein is found joining the back of the left common iliac vein, and the artery runs up behind the psoas major towards the L5 transverse process. After pelvic trauma, CT angiography may show contrast leaking from it, a branch of the internal iliac that can be embolised.

## Clinical notes

- If avulsed, the vein retracts into the psoas major or toward the foramen and bleeds heavily, which is why it is tied early and securely
- The artery's spinal branch at L5–S1 adds to the blood supply of the [cauda equina](https://durgical.com/en/anatomy/cauda-equina/)
- Pelvic and sacral fractures can tear the iliolumbar artery; bleeding from it is one of the sources treated by angiographic embolization

## Anatomical variants

- The artery may arise from the main internal iliac trunk, its posterior division or, less often, the common iliac artery
- The vein drains into the internal or the common iliac vein and is often double, so a second vein is looked for before the left common iliac vein is retracted

## Test yourself

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

## From which artery does the iliolumbar artery arise?

Usually the posterior division of the internal iliac artery.

## Why is the iliolumbar vein tied early in an anterior approach to L4–L5?

It is the key tether of the left common iliac vein; if avulsed it retracts into the psoas and bleeds heavily.

## Into which two branches does the iliolumbar artery divide?

A lumbar branch (psoas, quadratus lumborum, spinal branch at L5–S1) and an iliac branch (iliacus, ilium).

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

## Its names

**Official Latin (TA2)**
arteria iliolumbalis; vena iliolumbalis TA2 4304

**Official Spanish (DeCS)**
Arteria y vena iliolumbares

**English (TA2)**
Iliolumbar artery

## Related

- [Iliolumbar ligament](https://durgical.com/en/anatomy/iliolumbar-ligament/)
- [Common iliac veins](https://durgical.com/en/anatomy/common-iliac-vein/)
- [L5 vertebra](https://durgical.com/en/anatomy/lumbar-vertebra-spine-and-pelvis-l5/)
- [Iliacus](https://durgical.com/en/anatomy/iliacus-muscle/)
- [Psoas major](https://durgical.com/en/anatomy/psoas-major/)
- [Quadratus lumborum](https://durgical.com/en/anatomy/quadratus-lumborum-muscle/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Abdomen and Pelvis: Internal Iliac Arteries](https://www.ncbi.nlm.nih.gov/books/NBK537311/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/iliolumbar-artery/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/iliolumbar-artery/