It seems pretty straightforward—if the same procedure or service is performed on bilateral body parts, you append modifier 50 (bilateral procedure) to the procedure code for the services rendered. But, as is typical for medical coding, there is more to this.

First, physicians and coders must note that bilateral procedures apply to the exact same procedures on anatomic sites that are distinctly paired (mirror image). Use of modifier 50 does not apply to procedures on the skin even when procedures are performed on the skin of the right and left cheeks, arms, etc, because the skin is a single organ without laterality. Payers may allow informational modifiers LT (left) and RT (right) when procedures are performed on the skin of bilateral sites (eg, skin of both arms).

Modifier 50 is never necessary on a code that includes “bilateral” or “unilateral/bilateral” in the code descriptor. If a procedure is described by...

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