The Correct Coding Initiative is a special ruleset administered by CMS often called CCI Edits.
CCI Edits include rules for specific procedure code pairs that aren't normally allowed during the same visit, procedure codes that aren't allowed at all, or codes that aren't allowed in more than one visit in a day. These are published quarterly by Medicare and updated here: CCI Edits
Types of Edits
There are two types of procedure code pairs: Column1/Column2 codes and Mutually Exclusive Codes.
If Column1/Column2 codes are both submitted during a visit or day, Medicare will automatically bundle the codes together(i.e. will combine Column2 code into the Column1 code and only pay for one). If they are both timed codes the time for both should be combined and aggregated and reported to Medicare as the Column1 code.
In Mutually Exclusive Code Pairs the second column codes are not allowed with the first column codes.
Modifiers are codes that may be appended to Column 2 codes that allow an exception to the rule so the Column 2 code may be billed. The most commonly used modifier is the -59 which indicates that the two procedures are separate and distinct. When submitting the -59 modifier, the clinical documentation should clearly differentiate the distinct clinical services performed for each code.