same procedure different side- Modifier to use?

I coded a carpal tunnel surgery that got paid and during the global period the doctor performed the same procedure on the opposite side of the body. It came back denied as coding error. Is there a certain modifier I should have used on the 2nd surgery?

re: same procedure different side- Modifier to use?

If you appended an anatomical mod such as -RT/-LT to the first procedure and the 2nd call the carrier and point this out to avoid a written appeal. If not, I would try -58 or a written appeal to clarify I would most likely appeal and not use the -58.

re: same procedure different side- Modifier to use?

modifier -79