"LCD" stands for "Local Coverage Determination."
It is a document written for the locality covered by the Medicare contractor that services that region.
Among other things, it explains what the procedure is and the conditions that will satisfy the contractor's medical necessity requirements. More specifically, it tells you which diagnosis codes must be linked with the procedure for the claim to be reimbursed.
What if my claim isn't for Medicare? Well, most private insurance carriers start out with the Medicare LCD's, and modify them to their taste. So while they are not required to follow the Medicare contractor's rules, the LCD is often a pretty good indicator of how a private carrier will view the claim.