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I have a procedure described as an I&D with debridement. "Patient has a working AV fistula in the same arm. A vascular surgeon opened a lymphocele in the arm 15 cm, which produced bloody serous fluid, no apparent infection. Blood clots observed around base of the wound with no active bleeding. Cautery used for hemostasis of would edge. Culture taken. Attempted fistulogram by several attempts to access the brachial artery with ultrasound failed to obtain access. Wound packed open for future placement of wound VAC." I am finding unlisted procedure code 37799 to describe the open surgical portion of this procedure and 36147 with a -74 modifier for the attempted AV fistulogram. Is there a more appropriate CPT code to describe this procedure?