This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Trauma, Subject name: Surgery
A 70-year-old man is brought to the emergency department following a car crash. X-rays revealed a fractured rib on the left and a fracture of the right femur. A CT scan of the abdomen showed a left-sided retroperitoneal hematoma adjacent to the left kidney and no evidence of urine extravasation. The hematoma should be managed by which of the following? 
Select and explain. 
A. Observation, B. Exploratory laparotomy through a midline incision, C. CT scan-guided aspiration, D. Surgical exploration through a left-flank retroperitoneal approach
A: Observation
Answer: A: Observation 
Explanation: A small nonexpanding hematoma with no associated urine extravasation can be managed by observation with repeat CT scan or ultrasound. If the patient becomes hypotensive, exploration through a midline incision would be indicated.