Only a small fraction of transplant centers nationwide are willing to accept and transplant deceased-donor kidneys that they perceive as less than perfect, leading to lengthy, organ-damaging delays as officials use a one-by-one approach to find a willing taker. Now researchers have designed a formula they say can predict which donor kidneys are most likely to be caught in that process, a method that could potentially stop thousands of usable kidneys each year from being discarded.