Hi Pebble Beach,
I had the urodynamics test (2x). It is not a painful test, but I find it a bit uncomfortable and incredibly embarrassing
Basically you have a catheter inserted (in both ends in my case at least) while seated on a fake toilet. Your bladder is then filled with water, and measurements are taken at different points of emptying the bladder.
I had the test before and after surgery to detether my spinal cord last spring. Prior to surgery the test showed loss of bladder function; after surgery the test showed normal bladder function!
I also have cervical stenosis, but so far only very mild symptoms for that one.
Best of luck,