Coloured X-ray of a JJ stent (yellow tubing) in a urinary system. The stent has been inserted in the patient's ureter to keep it open and to allow urine to drain from the kidney to the bladder. It is often inserted to maintain urinary function until an operation, such as the removal of kidney stones, can be performed. The coiled end at upper right is in the kidney and the other end is in the bladder, neither of which show up on the X-ray.