A 35-year-old woman is admitted to the trauma unit after a fall from a 15-foot scaffold. She reports left-sided flank pain and has a contusion over the left costovertebral angle. Vital signs are stable: BP 118/74 mmHg, HR 88/min. Urinalysis shows gross hematuria (>100 RBCs/hpf). Contrast-enhanced CT scan of the abdomen and pelvis reveals a Grade III renal laceration of the left kidney with contained perinephric hematoma and no active extravasation. There is no evidence of collecting system disruption or vascular injury. What is the most appropriate management?