Google is your friend, though it helps if you spell things correctly
"infundibular stenosis"
Is supposedly pretty rare.
It has to do with the calyx of the kidney.
The calyx are part of the urinary collecting system and have to do with how the urine is passed from the kidneys to the bladder.
Sounds like you need to call your urologist back to ask for some clarification and explanation.
Maybe this link will be helpful to you:
National Kidney Foundation: A to Z Health Guide