Are you sure that your doctor said D11-D12 and not T11-T12. It doesn't seem that there are vertebrae (I assume that's what you were talking about) named that way. There are twelve thoratic vertebrae and they are numbered from T1-T12. In that case T11 and T12 are somewhere in the middle of your back. Hopefully this helps you get a start into understanding what's going on!
Also, if you call your docto,r I think they'll explain it to you
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