understanding How to use modifier 79

UNDERSTANDING HOW TO USE MODIFIER 79 

​ Per the Current Procedure Terminology® (CPT®) manual, the descriptor of modifier 79 is:
• "Unrelated procedure or service by the same physician during the postoperative period."
As indicated, this modifier is used to bill an unrelated procedure or service performed by the same physician during the postoperative period of a previous surgical procedure.
When a patient has surgery performed, there is a postoperative period -- a period after the surgery has been performed when additional surgical care related to the initial surgery is considered already covered (and paid for) by the allowance provided for the initial surgery. The postoperative period can be zero or 10 days (minor surgical procedure) or 90 days (major surgical procedure). (Note that some surgeries are considered so minor that they have a zero day postoperative period, usually a very quick outpatient procedure.)

Modifier 79 should be used when a surgical procedure is:

• Performed during the postoperative period, where the original surgery had a global period of 10 or 90 days.
• Performed by the same physician or physician of the same specialty within the same group, and
• Unrelated to the original surgical procedure

REMEMBER! 
When the 79 modifier is used, a new postoperative period for the second surgical procedure begins. Additionally, the remainder of the postoperative period of the original surgery is still applicable.

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References:
Medicare CMS Website
American Medical Association CPT
Coding Books
Payers Websites