A 62-year-old man with a 15-year history of type 2 diabetes mellitus and hypertension undergoes digital subtraction angiography (DSA) for evaluation of progressive claudication in the left lower limb. The angiogram reveals a 4 cm segmental stenosis of the left superficial femoral artery with delayed opacification of distal vessels. During the procedure, the patient develops sudden severe flank pain and hypotension. Repeat angiography shows contrast extravasation into the retroperitoneum. Which of the following is the MOST likely mechanism of this complication?