Today, 20 Americans will die waiting for a donated organ. Meanwhile, the United States’ transplant waiting list — more than 114,000 — will add a name every 10 minutes. Nova’s “Transplanting Hope” tells the story of the people who wait, those who give and those assigned the terrifying privilege of saving lives with transplanted organs.

The documentary, which airs on PBS stations at 9 p.m. Wednesday, takes viewers into hallways, conference rooms, airplanes, research labs and operating theaters where the life-or-death drama of organ transplantation takes place. It looks toward future technologies that could make procedures more successful. And it makes the stakes of a worldwide organ shortage clear.

Even if there were enough kidneys, lungs, hearts and other organs to go around, there would be other dangers to contend with. Patients’ bodies can reject organs intended to save their lives. They can face lifelong health complications, including blood cancers that can develop in bodies whose immune systems are suppressed after organ transplantation.

But the real enemy in “Transplanting Hope” is the clock. The wait for an organ can devastate a sick body, and the organ itself faces dangers as seconds tick between harvest and transplantation.

The documentary doesn’t deal just in organs. It also deals with people. As filmmakers track patients and donors, including an infant in need of a new heart and a young, comatose man whose organs could help others live, they lay bare the stakes of transplantation. Most transplanted organs come from people who will never live to feel the rewards of their sacrifice.

It can be hard to keep watching — not just the procedures but also the wrenching emotions experienced by patients, families and medical professionals. Still, the documentary’s title holds true. Although it may represent agony, each transplant also represents hope in the form of a living organ or piece of tissue.

If you’re not already an organ donor, you can sign up at ­