A 58-year-old man from rural Maharashtra presents to the emergency department with sudden onset of severe abdominal pain radiating to the back, associated with hypotension (BP 88/54 mmHg) and tachycardia (HR 118/min). He has a history of hypertension and smoking. On examination, a pulsatile abdominal mass is palpated. CT angiography with contrast shows a 6.5 cm infrarenal aortic aneurysm with acute dissection and retroperitoneal hematoma. Which of the following anatomical relationships explains why rupture at this level presents with retroperitoneal bleeding rather than intraperitoneal bleeding?