A 64-year-old male is admitted to the emergency department following a car accident. His pulse is 94 bpm, blood pressure 95/60 mm Hg, and HCT 30%. Severe hematuria is evident. Following resuscitation, his blood pressure is elevated to 120/80 mm Hg. A CT scan reveals extensive contusion confined to the left kidney and perirenal fat. His blood pressure declines to 80/40 mm Hg, and urgent laparotomy is performed via?