Donating a kidney: diagnosis

I thought I'd write about what I've been through recently, in the hope of it being useful to any who find themselves in a similar situation. I suppose each person's experience is different, but there must be similarities.
Anyway, 3 years ago my son joined us for a holiday in Scotland. My wife and I had already been there for a few days, walking in the hills and we were hoping my son would enjoy doing the same, the way he has done in the past.
This time, however was different. He seemed much less fit than us. Instead of walking a mile or so ahead, he was getting further and further behind. My wife was worried. I tried to shrug it off, thinking that it had been a long time since he had been away with us, he was doing a PGCE course and had little time to exercise.
As one final walk we made it up to the top of Ben Starav:

As a photo on the way up, with my son just about visible, this would be normal. But this was on the way down.
Back to his PGCE course he went. His illness got worse. He described it as feeling that his whole body was shutting down, which it was. He hardly ever slept. One visit to his doctor left him with a false diagnosis of depression. No criticism here just yet - he was fit and healthy and not a typical victim of kidney disease. Many of the symptoms - a sense of impending doom for instance - are similar. But when he asked for a blood test the doctor refused, saying "You're a teacher, you're depressed". That mistake and refusal of a simple request could have been fatal. When telling his mentor at school how ill he felt and how little he slept he was told something along the lines of "this is what it takes to be a teacher, if you can't stand the heat..."
Nevertheless, he passed his PGCE and got a great job which would mean him moving back in with us.
On his return my wife insisted he ask our doctor for a blood test. This was given and hours later we received a call which basically said "take him to hospital, now". He had suffered near total kidney failure and was on his way to a heart attack.
It was awful to see him in hospital, various lines attached to him. I felt guilty about brushing things off a few months earlier. It became clear that dialysis was not a permanent solution - it leads to a possible reduction of 20 years in life expectancy. Waiting for a transplant from the normal list could take years. A better way would be for a living donor to turn up - I knew it would be me and for some strange reason I knew it would be my left kidney.