U.S. Army Specialist Ricky Glenn Henderson flew back from Afghanistan in hopes of donating part of his liver to his dying grandfather.

The soldier has been undergoing tests since Wednesday at Baylor University Medical Center in Dallas to see whether he is a possible match, his grandfather, Ricky Homer, 62, told ABCNews.com. Homer spent four years in the U.S. Marine Corps and 16 years in the Army.

"I don't want to look back and say, 'Hey, I could have done something,'" Henderson, 21, told ABCNews.com.

Calling from Afghanistan, Henderson told Homer what he wanted to do, and Homer was shocked.

"He's like, 'Why? You're young,'" Henderson said. "I had to sit there and explain, 'You're my granddad. I want to do this. You still have stuff that you need to be around for.'"

(Photo Credit: KLTV)

Homer said he has a genetic condition called hemochromatosis, a genetic disorder that causes his body to absorb too much iron and store it in his liver and other organs. As a result, he has cirrhosis, or scarring of the liver, which doesn't allow it to function properly.

His grandson is his hero, Homer told KLTV, ABC News' Longview, Texas, affiliate.

"If I don't get the liver transplant, I die," Homer told ABCNews.com.

Dr. Giulino Testa, who directs the living liver transplant program at Baylor, said he found an abnormality in Henderson's platelet count and needs to be absolutely sure the liver donation will be safe before giving it the go-ahead.

If the transplant happens, he added, Henderson's liver will return to normal size within a few days and normal function within a few months.