Consideration of the potential courses of the common iliac artery.

We encountered a rare case of the left common iliac artery in a 92-year-old Japanese female cadaver during dissection practice for medical students. The artery entered into the small pelvis without branching to the external iliac artery. There, it went down slightly medially and then turned laterally and passed behind the first sacral nerve. The artery ran anterolaterally further and returned to the greater pelvis and became the external iliac artery, which continued to the femoral artery as usual. During the course in the small pelvis, the artery branched to give rise to each branch of the internal iliac artery. We speculate that in the present case, a communication between the median sacral artery and the superior gluteal artery, passing behind the first sacral nerve, enlarged and compensated the usual common iliac artery.