Paired Kidney donation can literally save multiple lives at once. This happens when someone wants to donate a kidney to someone specific like a friend or family member. If they're not a match for that person, they can put their name in the paired donation program.
This means they can match someone else who needs a kidney. The pool then opens wider to finder their loved one a kidney from someone else who is in the same situation.
You can also just get tested to donate a kidney because it's something you want to do to help someone who needs one. The need is so great for matching kidney's that this option may be someones only hope.
For more information on paired kidney donation: Go to http://uthealth.utoledo.edu/clinics/urology/transplant/index.html