A 36-year-old female presented 1 month ago with right sided flank pain and two proximal ureteral stones were seen on KUB (figure 1a). She had not seen the stones pass since that KUB and pain did not improve. Therefore, she underwent right ureteroscopy with laser lithotripsy and stent placement (figure 1b). Intra-operatively, only one of the stones in the proximal ureter was seen. The patient was discharged home the same day but returned to the emergency room 2 days later with intractable right flank pain. Based on the imaging in figure 1, what are you suspicious of?
A. Duplicated collecting system
B. Post-operative stent pain
C. Migrated stone into kidney