>>> and while we reported extensively on the u.s. troops serving in iraq and afghanistan , we haven't heard as much about some vital assistants accompanying them on those dangerous missions. we're talk about hundreds of dogs that have faithfully served and witnessed the horrors of war just like the troops. we get their story tonight from nbc's kerry sanders .
>> reporter: they're the dogs of war come home. like doc, a 4-year-old chocolate lab , who spent his deployments in afghanistan sniffing for roadside bombs and survived.
>> there is no real technology out there that can do what a dog can do.
>> now we'll take him into radiology.
>> reporter: and if they're wounded, they're medevaced to the walter reed of canine hospitals at lackland air force base in texas. like the troops they're assigned to patrol with, the dogs get top notch medical care when they're wounded like little scarlet here. but increasingly, doctors say they're finding dogs returning from war have something else. ptsd. post-traumatic stress disorder.
>> this is strictly a problem that we're associated with combat environments right now and prolonged deployments.
>> reporter: dr. walter berghart routinely gets videos from handlers in iraq and afghanistan who want to know why their dogs are no longer performing as trained. in one video the dog cowers when he sees uniformed iraqi soldiers . in another a dog trained to sit after sniffing a bomb instead tucks his tale between his legs and runs away.
>> if the dog misses one of these explosives, that could have really bad consequences not only for the dog but for the individuals the dog's working with.
>> reporter: which brings us back to buck. u.s. marine corps retired.
>> see he's backing up there.
>> is that from something that happened in afghanistan ?
>> i suspect that something happened to him in terms of bombs.
>> reporter: larry and lynette sergeant adopted buck when doctors could not treat his canine ptsd.
>> you can't help but love him when you look at him.
>> he's just afraid.
>> reporter: the family says unlike most labs, buck doesn't like to be around people. the best medicine, just like that for humans. understanding, love, patience, and sometimes these dogs are even prescribed puppy prozac.
>> five months ago he barely would let me lead him on a leash.
>> and so the idea that five months later we're sitting here this close, there's a foreign object , this camera so close to him.
>> it's incredible.
>> reporter: the dogs of war . just like some returning troops, now home with wounds that are hard to see. kerry sanders , nbc news, san antonio .