In reply to Noo Noo:
I was diagnosed with the kidney (and other effects) Polycystic Kidney Disease when I fell off a mountain bike about 20 years ago and suffered a bad kidney bleed. Since then I ski my age, have stopped ski randonee,avoid falling off when climbing and avoid rattling around on bikes. I find long hard days difficult and suffer flank pain on long back-packing or skiing days. I find that sticks help a lot with avoiding shock to my kidneys. I eat and drink very carefully, keep weight and blood-pressure under control, try to stay fit.
I'm 70 now and still enjoying the outdoors.. Good luck and just take things sensibly. To quote the cliché, learn to listen to your body.
It may be that you find some activities knackering because they are!