Q. A 5-year-old male presents to your clinic with a history of difficulty urinating and recurrent urinary tract infections. The patient's mother reports that he has been complaining of abdominal pain and has difficulty passing urine. He also has a history of enuresis and poor urine flow. His birth history is significant for lethargy, poor feeding, and failure to thrive. The patient remains in the tenth percentile for height and weight. On physical examination, he is in no acute distress, and vital signs are within normal limits. You detect abdominal distention and mild tenderness on palpation of his abdomen. There is no evidence of any genital abnormalities. You order a voiding cystourethrogram (see image). An ultrasound of the urinary tract is performed, which confirms the findings. Based on the information you have at this point in time, which of the following is the most likely diagnosis?