I'm delighted you got some good news back, after all the anxiety! Like others, I'll be hoping to hear later how the complete results looked.
As someone who is very good at blaming myself for things, and worrying, as well - please be gentle to yourself. You really sound like you are doing as much as you can, with love and concern for all your family. It is not expected, not to BE expected, that any of us can be perfect or meet everyone's needs; but that we do our best, find what help we can, and love them.
I hope you will find that your son's issues really are limited to minor kidney problems. Forgive me if this is too long, or too personal, but in a way, I think it's important, if not for you (God willing! - though you may see some of this with your older son), for others whose children have may be born with obvious problems, or develop them, later. Having had health problems that were very severe from early childhood till perhaps the last two years (when, after long treatment, and rehabilitation effort, they're miraculously reduced to 'manageable', if I do not wear myself out) - even at the worst times, times of real and prolonged suffering, I have been so glad to be alive.... My mother couldn't prevent my getting an infection, in utero, she did not, could not, know she had. She could not make things go perfectly - or, often, even 'well'. But she loved me and did what she could to take care of me, both as a child, and for years, when almost entirely incapacitated, in my twenties. (A time when, among other things, I went from being a passionate reader, loving to cook, and attending college while I worked part-time, to being unable to walk, read, or remember what had happened earlier in a day. At times, I could not feed myself.) Perhaps many people, looking ahead, seeing the struggle of my childhood, and those later years, and not seeing the moment I am in now, would have thought my life was not worth living, or was all too sad, too hard, to be dealt with. But, even in the terrible times, that was only one side of the story, not the best or most important one. - And that's how we felt, then, without denying the pain and loss we also faced. Giving your children love and the privilege of the best life they can have, whatever it might be - that is enough of a gift. People who think everything needs to be perfect to be worth having do not really understand the value of existence (or of much else, I believe). A loved life is worth having. Finding what good you can in the worst times is a saving grace. And sometimes - sometimes - astonishing things do happen. There are some residuals from all the years of ill health, but I am happily married, largely healthy, off all medication, fairly active, able to do things I love (read, cook, explore the great city I live in - on foot!, talk, go to cheap theater and concerts, and much more) as long as I balance it all with rest. There were times it was not clear I would ever walk, again. Yet, last summer, I ran a 5k, and came in in the top half of the race (after only 8 weeks of running). And now - I am expecting twins, who are doing beautifully. (As I've been extensively treated, I am unlikely to pass this to them.) None of this would I have believed could really happen. I saw too much go wrong to be so hopeful. I do understand the nature of intractable problems (things which no amount of effort can make 'alright'), but also the surprising quality of life, and the passionate desire you can have to live, the love of doing so, and possibility of doing so well, in limited circumstances. Please, let me also agree with anyone who suggests that there can be unexpected plus-sides even to apparent tragedies. (One doesn't have to deny the tragedy, or falsify reality, to feel that way.) My family is warm and close, and deeply appreciate each other. Many people with easier outward circumstances end up with much less than we have, and have had.
Plus, you know, I may owe my mother the struggles in some sense she's not responsible for, but I also, in two different ways (at least), truly owe her my life. I would never blame her for the part she would have spared me, if she could have done anything to change it. I'm sorry to be so long, but I think not everyone who might want to say these things is fortunate enough to be able, as I am, now. And I do hope that this might be reassuring, if only as against the worries and possibilities we may face.