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Collateral circulation in pelvis briefly as 15 marks answer

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Collateral Circulation in the Pelvis

Introduction

The pelvis is exceptionally well collateralized, with a multitude of anastomoses between both visceral (organ-supplying) and parietal (wall-supplying) branches. Collateral circulation operates on the principle that an afferent vessel originating proximal to an occlusion anastomoses with an efferent vessel distal to it, restoring flow. These pathways become clinically significant in aortoiliac occlusive disease (Leriche syndrome), pelvic trauma, embolization procedures, and vascular surgery.

Pelvic Arterial Anatomy - Basis for Collaterals

The main arterial supply to the pelvis comes from the internal iliac artery (hypogastric artery), which divides into:
  • Anterior division: umbilical, obturator, internal pudendal, inferior vesical/vaginal, middle rectal, uterine arteries
  • Posterior division: iliolumbar, lateral sacral, superior gluteal arteries
Both divisions contribute extensively to pelvic collateral networks.

Major Collateral Pathways

1. Distal Aortic / Common Iliac Occlusion (Leriche Syndrome)

When the distal aorta or common iliac artery is occluded, the internal iliac artery is reconstituted through:
  • Lumbar arteries anastomosing with the iliolumbar artery (branch of posterior division of internal iliac)
  • Lateral sacral arteries receiving flow from above
This is the primary parietal (paraspinal) collateral route.

2. Aortoiliac Occlusion - External Iliac Reconstitution

In aortoiliac occlusion, the external iliac and common femoral arteries can be reconstituted via:
  • Lower intercostal and subcostal arteries → lumbar arteries → ascending branch of the deep circumflex iliac artery → external iliac artery
  • Iliolumbar artery reconstituting the internal iliac, which then communicates with the external iliac

3. The Winslow Pathway (Subclavian-to-External Iliac)

A long-range collateral from the upper trunk to the lower limb:
Subclavian artery → Internal thoracic artery → Superior epigastric artery → Inferior epigastric artery → External iliac artery
This pathway is critically important in severe peripheral arterial disease. Harvesting the internal thoracic artery for CABG in a patient with aortoiliac occlusion can precipitate severe lower limb ischemia - making preoperative angiographic demonstration of this pathway essential.

4. External Iliac Occlusion

Collateral flow is provided by:
  • The Winslow pathway (as above)
  • Internal iliac to external iliac anastomoses via:
    • Iliolumbar artery (posterior division of internal iliac) → deep circumflex iliac artery → external iliac
    • Obturator artery → anastomoses with inferior epigastric artery (pubic branch)

5. Internal Iliac (Hypogastric) Occlusion

Collateral flow comes from transverse pelvic collaterals:
  • Contralateral lateral sacral arteries (cross-pelvic anastomoses)
  • Distal branches of the contralateral obturator artery and contralateral internal pudendal artery
  • Median sacral artery (from the aorta directly) providing direct flow
  • Iliolumbar and superior gluteal arteries receiving retrograde flow from the ascending branch of the lateral circumflex femoral and deep circumflex iliac arteries

6. Trochanteric Anastomosis

At the trochanteric fossa, a rich anastomotic ring is formed between:
  • Superior gluteal artery (posterior division, internal iliac)
  • Inferior gluteal artery (anterior division, internal iliac)
  • Ascending branch of the medial circumflex femoral artery
  • Ascending branch of the lateral circumflex femoral artery
  • Deep circumflex iliac artery
This anastomosis bridges pelvic vessels with femoral vessels.

7. Cruciate Anastomosis

Located at the upper thigh, formed by:
  • Lateral circumflex femoral artery
  • Medial circumflex femoral artery
  • Inferior gluteal artery
  • First perforating branch of the profunda femoris

8. Rectal (Hemorrhoidal) Anastomoses

A classic visceral collateral network within the pelvis:
ArteryOriginLevel
Superior rectal arteryInferior mesenteric arteryUpper rectum
Middle rectal arteryInternal iliac arteryMid rectum
Inferior rectal arteryInternal pudendal arteryLower rectum/anal canal
These three arteries form a continuous submucosal plexus, important in rectal surgery and portal hypertension (inferior mesenteric - portal communication via superior rectal → hemorrhoidal plexus).

9. Vesical Anastomoses

The bladder receives supply from multiple anastomosing branches:
  • Superior vesical artery (from patent umbilical artery)
  • Inferior vesical artery (in males) / Vaginal artery (in females)
  • These form a vesical plexus with cross-anastomoses

10. Uterine and Ovarian Anastomosis (Females)

The uterine artery (branch of anterior division of internal iliac) anastomoses freely with the ovarian artery (direct branch from the abdominal aorta) along the lateral border of the uterus. This is why ligation of the uterine artery alone is insufficient to completely devascularize the uterus.

Diagrams

Fig. 11.26 - Trochanteric and Cruciate Anastomoses:
Trochanteric and cruciate anastomoses of the hip and pelvis
Internal iliac artery and pelvic arterial branches:
Pelvic arterial branches and internal iliac distribution

Clinical Significance

Clinical ScenarioRelevant Collateral
Leriche syndromeLumbar → iliolumbar → internal iliac
CABG with PADWinslow pathway must be preserved
Pelvic hemorrhage embolizationBilateral embolization needed due to rich cross-pelvic flow
Uterine artery ligation (PPH)Bilateral ligation required; ovarian artery compensates
AAA repairPreserve internal iliac to prevent colonic/gluteal ischemia
Rectal cancer surgeryRectal arterial arcade must be considered

Summary

The pelvis has one of the richest collateral networks in the body, explained by:
  1. Multiple bilateral symmetrical vessels that cross-anastomose
  2. Vertical communications between abdominal (aortic) branches and pelvic vessels
  3. Visceral anastomoses between IMA, internal iliac, and pudendal branches
  4. Peripheral anastomoses at the trochanteric and cruciate levels linking pelvic to femoral circulation
This redundancy allows tolerance of single vessel ligation (e.g., internal iliac ligation for pelvic hemorrhage) without catastrophic ischemia, but bilateral or multilevel occlusions may overwhelm these pathways.
  • Imaging Anatomy: Text and Atlas, Volume 3 - Bones, Joints, Vessels and Nerves, pp. 357-358 (Arterial Collateral Network of the Pelvis)
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