Serious stuff, I can't recall anyone racing at a good level with only oe kidney, although having two seems to be a bit of mother nature redundancy, as you can function well on just one. A relative of mine did for about 40 years. Whether the extra strain of racing would be tolerable for a one kidney rider, it's difficult to say, but I suppose the medics will be able to offer some guidance. Spleen not so much of an issue, Geraint Thomas lost his after a crash some few years back, and he's doing OK!
The important thing is to get well, then worry about whether racing at world tour level is possible. At a later stage in a career, the DS or other team support role may be an option if full on racing is out.