Discovered I had PKD in 2000 whilst I was working for a regional. Had to have a brain scan to ensure no complications, but after that have had no problems. Now work for Q and it was not a problem during pre-employment testing.
Best way to go about it to have your annual checkup just prior to your annual aviation medical. Take in a letter from your specialist and as soon as a DAME sees a documet giving you a clean bill of health in terms of kidney function and blood pressure (even if controlled by medication) they are happy to pass you without further investigation. In the end all they are looking for is someone ELSE to take the rap.
At my last medical my DAME told me CASA now require a few more tests for an initial medical than they did a few years ago, but in my experience recurrent medicals are pretty much routine.
Stay fit, healthy, drink plenty of water and you should have no problems.
Good Luck.