Final answer:
A temporary tube called a stent can be inserted into the renal pelvis when there is an obstruction in the ureter to relieve the obstruction and allow urine to flow.
Step-by-step explanation:
When there is an obstruction in the ureter, a tube called a stent can be inserted temporarily into the renal pelvis. This stent helps to relieve the obstruction and allows urine to flow from the kidney to the bladder. The stent is usually inserted through a surgical procedure and can be removed once the obstruction is resolved.