On the left there is a normally positioned double J stent with pigtails in the pelvis and bladder (yellow arrows).
On the right side is an abnormally placed double J stent; superior migration of the distal pigtail into the ureter leads to a loss of the pigtail appearance in the proximal and distal pigtails (black arrows). Twisting of the stent is also noted in the right renal pelvis (orange arrow)