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I need clarification regarding code 36818 vs. 36821. My auditor is stating that 36818 is used only for transposition where the vein is transposed in location via a tunnel, and that 36821 is the correct code. Per the op report I believe the correct code is 36818. 

"Next a 10 blade was then used to make an incision over this previously marked area through the epidermis, dermis, and subcutaneous fat. Bovie electrocautery was used for hemostasis. The brachial artery and the cephalic vein were dissected out, and 5000 units of heparin were administered. Cephalic vein branches were tied off. The cephalic vein and it was flushed out with heparinized saline. The end of the cephalic vein was spatulated, and end-to-side arterio-venous anastomosis was made with 6-0 prolene sutures after brachial artery arteriotomy. The brachial artery had great forward and back bleeding, and the fistula was flushed before closure. Soft tissue flaps were raised bilaterally, and the deep layer was closed with interrupted 2-0 vicryl sutures." 

Does this sound like code 36818 or 36821? Please help!