At any given time, there are about 13,000 people waiting for a liver transplant in the United States. Whether the cause is a virus, alcoholism or a bit of genetic bad luck, they’re all suffering while sick and scarred livers struggle to clean their blood. Over time, their intestines bleed. Fluid builds up in their legs and their chests. Their skin turns sallow. Confusion sets in. The only cure is to swap the old liver for a healthy one. Each year, about 8,000 people will get that chance. The rest will wait, getting sicker.