Q. A 32-year-old male was admitted yesterday with complaints of left flank pain and difficulty passing urine. He has no known medical history, and denies experiencing similar episodes. A urinalysis performed on admission demonstrated sterile hematuria. A complete blood count and metabolic panel were within normal limits. Staff report the patient did well overnight with no new complaints or symptoms. You ordered a CT scan of his abdomen and pelvis with IV contrast (see image), and the radiology report is available this morning. You review the findings, which include evidence of left ureteropelvic junction obstruction with dilation of the renal pelvis and proximal left ureter, slightly atrophic left renal parenchyma, no hydronephrosis or hydroureter, no suspicious renal mass, and no free fluid or lymphadenopathy. Based on these results, you request a urology consultation. Which of the following procedures is most likely to provide definitive treatment for this patient’s condition?