I think I have a perfect "solution" to this guy's snort. OK. Considering that he's taken the [entirely bizarre] notion of considering internal organs (no matter where they came from) the sort of things that couples splitting have to divvy up and share? Let's liken this kidney to one of their children, then. Or the family pet. Etcetera, etcetera. Seeing as how one can't cut children, dogs or, in this case, organs literally in half, shared custody seems the most sensible route.
If this dude "loves" his ex-kidney so much? Problem solved. Force him to have joint custody of it, meaning he gets to 'look after it' every other weekend per month. Which, of course, also means that he'd have to spend those weekends with the
vessel of said kidney.
I'm pretty sure he'd drop the lawsuit in a hurry

...