But there is hope that doctors may soon be able to regrow a penis from the smooth muscle and endothelial cells of patients like Silva. Advances in regenerative medicine have surged during the past decade. At the Wake Forest Institute for Regenerative Medicine, a team led by Anthony Atala reported last year that they had regenerated the penises of 12 New Zealand white rabbits. Once they healed, the rabbits were placed in cages with female rabbits. All attempted copulation within one minute and four females became impregnated.
Can he grow a penis for Silva? "We are always cautiously optimistic. This still requires a lot of work to make sure it works well,'' Atala said in an interview. "As much as it works in the laboratory, it may not work in the human."
"But," he added, "we have a good history. Hopefully this holds some promise for the future."
Atala is seeking regulatory approval to begin experimental penile regeneration in humans. He has met with Silva to discuss the procedure and said he wants to move forward "as expeditiously as possible," though he declined to provide a more specific timeframe.
Still, even if surgeons can physically rebuild genitals, making them work effectively and pleasurably is vastly more challenging. Achieving erection, orgasm and ejaculation involves a complex interplay of sensory nerves, muscles and blood-vessel functions, any or all of which may have been damaged by an IED blast.
"Even if you can regenerate tissue, it doesn't mean you can make that tissue function exactly the way it did before -- mostly because of nerve function,'' said Robert Dean, an andrologist who is Walter Reed's lone specialist in sexual dysfunction.
'WHO'S GOING TO WANT TO BE WITH ME?'
A genital wound doesn't mean the end of pleasurable or productive sex, however, according to Dean and other specialists. It's a common misconception, Dean said, that sex must include an erection, orgasm and ejaculation. "After an injury, the ejaculation function may be gone, but orgasm isn't," he said. "Erections may be difficult to achieve, but orgasms are still possible."
That's the theory. But predicting how well individual genital-wound patients will recover is nearly impossible, doctors admit.
Much is unknown about the secondary effects of a powerful blast on human organs. Apart from the obvious physical damage, the concussive blast wave seems to affect sexual function in ways that are not clear. Byler, for instance, suffered little visible physical damage to his genitals, but his testosterone levels and sperm count dropped alarmingly after he was injured.
He and many other genital-wound patients are given replacement doses of testosterone. Low testosterone levels can depress sex drive and decrease energy levels, but the treatment often requires precise dosages and a lengthy process of trial and error. And often, its effects are masked, as many patients are also taking a cocktail of other drugs for pain and anxiety or to control swelling and fight infection.
It's a situation that breeds intense frustration. Genital-wound patients are anxious to know what their sexual future looks like. But doctors at Walter Reed often are unable to reassure them that their sexual functions will ever return in whole, in part or at all. It can take a year, even two, for answers to begin to emerge, Jezior said.
Even then, he said, "We absolutely do not know how well their reactions will be with what they have remaining, how functional they will be. It takes a lot of time to heal, a lot of recovery, every part of the body has to heal before your erections become what will be their end-state.''
Some patients, he added, "will not get back to a functional state.''
But it can be difficult to determine who will recover, and how much, medical officials said, largely because there is a relative paucity of data on the long-term medical and psychological effects of the available treatments and the wounds themselves.
That uncertainty can add yet another crushing psychological burden for young men already struggling with the loss of arms and legs.
"You hear a lot of, 'This is the best we can do, but the fact of the matter is, we have never seen this type of injury before, so we [doctors] really don't know what to tell you,'" said Byler, speaking of his experience as an amputee and genital-injury patient at Walter Reed.
Byler said he never even saw a urologist until four or five months after he was wounded. "There's a lot of things they can do for limbs that are lost, like my legs -- but no one really addresses the genitalia,” he said. “You need someone to come look at the damage and give you an honest assessment of what they think it's gonna be. Because otherwise you're left wondering, who's going to want me? Who's going to want to be with me?''
Doctors at Walter Reed acknowledge having long failed to recognize that while young men may accept the loss of a limb, even the loss of several limbs, they are often far more devastated by damage to their genitals.
"There certainly was a disconnect," said Jezior. "It was an eye-opener for us that there is a grieving when it comes to significant injury to the genitalia that needs to be dealt with.'' Still, he insisted that the care provided to genital wound patients at Walter Reed is "pretty incredible, with a lot of support.''
'WE SAVED HIS PENIS'
Mark and Heather Litynski, however, did not feel supported after Mark was wounded. Their experience was bitter, frustrating and far from the future they had imagined.
They grew up two miles apart in the Minneapolis suburb of New Hope. When Mark shipped out to Afghanistan in September 2010, Heather went home to wait for his return.
She was holding down a temporary job at Starbucks in November when two Marines arrived, accompanied by her mother and sister. Mark was alive, they told her, but in critical condition with "severe lower torso injuries.'' They handed her a terse medical report describing his wounds. When she read "bilateral [both legs] above-knee amputations," Heather collapsed to the ground in shock.
It was far worse than she had feared. But he was alive.
"When I found out, I started crying, but very quickly I got over it because you're just so glad they're alive and doing well," Heather said.
Two days passed, an agony of waiting, before doctors could talk to Heather about the extent of Mark's injuries. There were a lot of other things to worry about -- the potential for deadly infection, of possible brain damage, the trauma of losing two legs and his arm. But one thing the doctors said hit home: "We saved his penis!''
"'Saved his penis!' Got something!" Heather recalled with a chuckle.
Mark has also accepted his wound, just as he has gotten used to his wheelchair, his prosthetic legs and mechanical arm. "When I found out about it [his testicle loss] I was kind of ... you know, 'Should have done the sperm-freeze thing,''' he said. "But ... we're making it through. It's not the end of the world.''
Of course, it wasn't as simple as that.
As surgeons at Walter Reed were working to repair Mark's abdominal wounds and shape his leg and arm stumps, they also began reconstructive work on his penis. They prescribed doses of Viagra or Cialis to see if he could get an erection. A duty nurse administered the first dose while Mark had a full-length catheter inserted in his penis. His erection was painful.
But stimulation is necessary and common early therapy for genital-wound patients, said Dean, the hospital's sexual-dysfunction specialist. "Even though they are not really close to wanting to use it, because they have physical therapy to go through and pain issues, we start rehab therapy to see what effect that has, because we don't want the [penile] tissues to atrophy,'' he said.
Severely wounded patients like Mark typically spend a few months in intensive care at Walter Reed. Then they transfer to an apartment in one of the comfortable new housing units at the hospital and continue their physical and occupational therapy as outpatients. Once Mark got a set of prosthetic arms and learned to walk on his new prosthetic legs, he joined other wounded patients on fishing trips, even a snowboarding in Vail, Colo., just over a year after his injury.
Things weren't easy, though. "He was very affectionate before, he used to always have his arm around me, hold my hand, just come by and kiss my head,'' said Heather. "That's how he was.'' But as his physical wounds healed, the couple's sense of intimacy did not return. Nor did Mark's sex drive. He was lethargic. He had ''zero'' desire, she said.