A new record for chained kidney transplantations has been set in the United States. It involved 30 transplantations across the country between March and December last year, which linked living donors to recipients whom they were unlikely ever to meet.

Chained transplantations start with a single altruistic donor. If this donor’s kidney is used to help a recipient who has been denied a transplant from a relation who was willing to donate but was unable to do so because of immunological incompatibility, then the chain can continue if that relation remains willing to donate anyway. That kidney goes to the next recipient in the chain, who also has a willing but incompatible relation, prepared once more to reciprocate the gift by donating onwards. Technically such a chain need not end, but people are excluded who have no relation or partner who is willing to keep the chain going.

The 30 strong chain in the US has been anatomised by the New York …