General Surgery Coding Alert

Test your coding knowledge. Determine how you would code this situation before looking at the box below for the answer.
Question: Our surgeon performed a thrombectomy several weeks after placing an arteriovenous (AV) fistula. We reported 36833 for the procedure, but the payer denied the claim. How should we have coded this? Michigan Subscriber  

Answer: The problem may be your diagnosis code or your use (or lack of use) of modifiers. Thrombectomies performed during the global period of the AV fistula's creation are not bundled, but the diagnosis code you link to the procedure can make a difference. Although the patient's renal failure is indirectly responsible for all the symptoms, the immediate cause of the thrombectomy and/or revision is clotting of the fistula. Therefore, the primary diagnosis code for the revision/thrombectomy would be 996.73 (Other complications of internal [biological] [synthetic] prosthetic device, implant, and graft; due to renal dialysis device, implant, and graft), which includes embolus and thrombus. In addition, if the revision/thrombectomy occurs within the global period (90 days) of the fistula's creation, you should append modifier -79 (Unrelated procedure or service by the same physician during the postoperative period) to 36833 (Revision, open, arteri-ovenous fistula; with thrombectomy, autogenous or non-autogenous dialysis graft [separate procedure]). Note that each revision within the original procedure's 90-day global period is separately billable. Some experts suggest using modifier -78 (Return to the operating room for a related procedure during the postoperative period) in the above circumstance, but the fistula repair is related to the underlying illness not to the fistula's creation and is therefore not strictly a complication of the earlier procedure. Payers have different guidelines, however, so you should check if your payer considers the repair a complication of the original procedure before billing for it.