Ureter stent. Coloured X-ray of the abdomen of a 39 year old male patient suffering from a kidney stone, showing a stent inserted into his ureter. The ureters join the kidneys to the bladder. Here the pig tail stent (green) runs from upper to lower right. Insertion of the stent has pushed the kidney stone (calculus), which blocked the ureter, back up into the kidney (not seen). The stent keeps the ureter open allowing urine to flow from the affected kidney into the bladder. The kidney stone will be removed surgically or will be broken up by shock-wave lithotripsy. Spine bones are at centre; the pelvis is at lower frame.