Besides slight differences between the arteries of the two sides, in length and direction, by no means of constant occurrence, the common iliac arteries vary in their place of origin, and in the point at which they divide.
The place of origin of the common iliac arteries coincides with that of the bifurcation of the aorta, the variations in which have been already noticed. The height at which these arteries divide is subject to great variety. In two- thirds of a large number of cases, the place of division ranged between the middle of the last lumbar vertebra and the upper margin of the sacrum ; in one case in eight it was above, and in one case in six below that space. Most frequently the left artery was found to divide lower down than the right. The length also was observed to differ much in different instances. In five- sevenths of the cases examined, it varied from an inch and a half to three inches ; of the remaining cases, in about half, the artery was longer, and in the other half, shorter ; the minimum length being (only in one case) less than half an inch, and the maximum four and a half inches. In estimating the relative lengths of the right and left arteries, it was found that the right was the longer in sixty-three, and the left in fifty-two, whilst the two were equal in fifty-three. In one instance, recorded by Cruveilhier, (" Anat. descript." t. III., p. 186), the right common iliac was wanting, and the internal and external iliacs of that side arose as distinct branches from the aorta.
From Quain's anatomy.