Prisoner David Patterson, who is an inmate in California, caused a huge stir in the medical community when he asked to give up his kidney for his 16-year-old daughter. While it is not uncommon to donate a single kidney from one living person to another, what was strange was that he was offering up his only remaining kidney.
He had already donated the first one to his daughter, whom he had previously had little contact with. She was in need of a replacement for the first one he gave her because it was failing. The problem for the medical community was whether to allow this second donation.
Donating one kidney is allowed because a person can live a long, fairly normal life with just one kidney. The reason a person cannot donate a second kidney is because it significantly shortens their lifespan and they must be on dialysis regularly to survive.
For the medical community, this is a sacrifice that cannot be made. Medical experts cannot be expected to help one person give up their organs and life for the sake of another person. They can only donate what they can live without in a reasonable manner.