Registration CT images with Ants Rregistration or Elastix

Hi everyone,
I have a problem with the registration of two abdominal CT scans. In particular, the two cases have different sizes and different characteristics that I show below.

My goal is to accurately register the two CT because I want the kidney stones (which are shown in the basal ct) inside the calyxes of the kidney (shown in the late ct).

When I do the registration with Elastix or ANTS registration the result is not accurate.

I show the segmentations of the two volumes to emphasize how the two ct are distant from each other before registration.
(yellow: late, purple: basal)
Then I do the registration with Ants registration, rigid+affine (or Elastix, the final result is the same). It’s clear that the registration is not accurate. I show you how the kidney stones are outside the calyxes.

Is there something I’m doing wrong? Do you have any suggestions for improving my work? Do I have to do some kind of manual pre-registration?
Thank you all