Renal Trauma with Vascular Pedicle Injury

A 32-year-old cyclist presents to the emergency department after a high-speed deceleration injury with left flank pain, gross hematuria, and flank ecchymosis. He is hemodynamically unstable (HR 124, BP 88/54 mmHg) despite 2 units of packed red blood cells and crystalloid. Contrast-enhanced CT of the abdomen and pelvis with arterial, nephrographic, and delayed excretory phases is performed. The structure marked **A** in the diagram shows non-enhancing devascularized renal parenchyma. What is the most likely underlying vascular injury responsible for this imaging finding?