Yup, thats quite common in urinary obstruction when no obvious cause is found and people land up having stent in the ureter. Having said that, it is found to deal with many subtle and/or temporary obstructions including cell debris, small kidney stones and so on. Thus it protects the kidney from permanent damage. But it cant be permanent and once basic problem is solved and obstruction relieved, we can get rid of the stent at any later date before it itself becomes a nidus for infection!!!