It maintains the Ureter open all the time, It has multiple holes and even if there is block in the path urine can travel through these holes and prevent back pressure changes and Kidney destruction, It helps the ureter dilate. The ureter or the passage from the Kidney to the urinary bladder enlarges to about two and a half to three time, It helps prevent strictures or narrowing during the healing process. If there is injury or obstruction due to a stone the healing process would narrow the lumen [tube]. The DJ stent prevents this from happening.