A 6-year-old boy presents to the ED with severe left flank p…
A 6-year-old boy presents to the ED with severe left flank pain, nausea, and decreased urine output for 12 hours. He has no prior medical history. Vital signs: T 38.5C, HR 138, BP 92/58. Exam shows left CVA tenderness and abdominal guarding. Labs: WBC: 17,000 Creatinine: 1.6mg/dL (baseline unknown) CRP: elevated UA: positive nitrites, leukocyte esterase, moderate hematuria Renal US: shows moderate left hydronephrosis with a 7mm obstructing distal ureteral stone and debris in the collecting system. Which of the following is the most urgent next step in management?