When a woman surviving on dialysis discovers she was adopted after her sister offers a kidney only to discover it doesn't match, she must go on a journey to find her real family for a donation. (36 words)
This version tags the woman with the greater motivation as the MC. She would also be the one who has to undergo the greater struggle: she must overcome all the obstacles and complications while being tethered to dialysis treatment which typically must be done at least 3 times a week.
Whatever, the story is ripe with emotionally dramatic possibilities. Because after she finds her family, she must persuade one of them to donate (and initially, of course, no one will.) And she will also force her real mother to confront her painful past and confess to all the ugly truth of why she put her daughter up for adoption. Which was...?
Best of luck with the story.