SN6 SHORT NOTE 5M ★ High-yield

Describe the internal iliac artery with its branches and collateral circulation.

Anatomy · 1st Professional — Pre-Clinical

The internal iliac artery is the chief artery of the pelvis, supplying the pelvic viscera, the pelvic walls, the perineum and the gluteal region.

Arises from the bifurcation of the common iliac artery at the level of the sacro-iliac joint (L5–S1)
About 4 cm long; divides into an anterior and a posterior division at the upper border of the greater sciatic foramen

Division	Branches
Posterior division	Iliolumbar; lateral sacral; superior gluteal
Anterior division — parietal	Obturator; inferior gluteal; internal pudendal
Anterior division — visceral	Superior vesical (from the umbilical artery); inferior vesical (male) or vaginal (female); middle rectal; uterine (female)

Mnemonic for the posterior division — "I Love Sex": Iliolumbar, Lateral sacral, Superior gluteal
All three posterior branches are parietal; the visceral branches all come from the anterior division
The obliterated umbilical artery persists as the medial umbilical ligament after giving off the superior vesical artery

Anterior — the ureter crosses in front of its origin at the pelvic brim; the ovary in the female
Posterior — internal iliac vein, lumbosacral trunk, sacro-iliac joint
The ureter crossing the bifurcation of the common iliac artery is the standard landmark for identifying it in pelvic surgery

Anastomosis	Vessels involved
Iliolumbar with lumbar arteries	From the aorta
Lateral sacral with median sacral	From the aorta
Middle rectal with superior rectal	From the inferior mesenteric
Uterine and ovarian arteries	Ovarian from the aorta
Obturator with inferior epigastric	From the external iliac

Internal iliac artery ligation is used for postpartum haemorrhage, placenta accreta and pelvic trauma when other measures fail; the ureter must be identified and the posterior division spared where possible
Uterine artery embolisation treats fibroids by the same principle, relying on collateral supply to preserve the uterus
An abnormal obturator artery arises from the inferior epigastric instead of the internal iliac in about 30% of people, and runs close to the lacunar ligament — the "artery of death" in femoral hernia repair
Pelvic fracture tears branches of the internal iliac and causes concealed retroperitoneal haemorrhage of several litres; controlled by pelvic binder and angiographic embolisation
The superior gluteal artery leaves through the greater sciatic foramen above piriformis and retracts into the pelvis if torn, making surgical control difficult

All questions in Pelvis & Perineum