A 58-year-old man with a 10-year history of type 2 diabetes and hypertension presents with acute-onset severe epigastric pain radiating to the back, associated with hypotension (BP 90/60 mmHg) and tachycardia (HR 110/min). CT angiography of the abdomen reveals a 5 cm infrarenal abdominal aortic aneurysm (AAA) with a crescent-shaped area of high attenuation within the thrombus, adjacent to the aortic wall, and extravasation of contrast into the periaortic space. Which of the following angiographic findings best explains the acute clinical presentation?