Question: Our surgeon treated a patient with severe blockage of the right carotid artery by performing an endarterectomy, making an incision along the neck and opening the artery to remove the thrombus and plaques. What are the correct procedure and diagnosis codes? California Subscriber Answer: The appropriate procedure code is 35301 (>Thromboendarterectomy, including patch graft, if performed; carotid, vertebral, subclavian, by neck incision).> The correct diagnosis code is I65.21 (>Occlusion and stenosis of right carotid artery). The I65 category describes >Occlusion and stenosis of precerebral arteries, not resulting in cerebral infarction. The fourth character of this code indicates that the condition occurs in the carotid artery. The fifth character indicates that it is the right artery.>