Extraspinal Vascular Emergency on Lumbar Spine Magnetic Resonance Imaging (MRI): A Case Report.

Acute back pain is one of the most frequent chief complaints in the emergency department (ED). Lumbar spine MRI is commonly obtained in this setting, and radiologists typically focus on musculoskeletal or neurologic etiologies. However, a systematic evaluation of extraspinal structures is essential to identify less common but potentially life-threatening causes of back pain. We report the case of a 70-year-old man with hyperlipidemia who presented with one week of progressive lower back, left hip, and left scrotal pain. Lumbar MRI revealed flow voids contiguous with the iliac arteries, an extraspinal feature that prompted immediate CT angiography (CTA). CTA demonstrated a spiral abdominal aortic dissection with the false lumen perfusing the iliac arteries, with associated bilateral iliac aneurysmal dilatation. Notably, recent hemorrhage into the left psoas muscle was also identified. The contained psoas hematoma produced left-sided obturator and psoas signs and explained the patient's constellation of symptoms. This case highlights the lifesaving importance of a structured approach to extraspinal findings on spinal MRI.