He took photographs of some of the heartbreaking conditions, like a hospital that used old beer bottles for intravenous drips.
For his efforts with the relief agency, the doctor received the Friendship Medal from a seemingly grateful North Korean government, reports CBS News Correspondent Barry Petersen.
But then he got a glimpse at North Korea's dirty little secret: It is the stone age in the countryside, but the gilded age for the elite.
"In Pyongyang, the capitol city, there is plenty of money," Vollersten says. "And there is no need for those pictures. There is no need for starving children."
It's a ruling class that squanders millions on everything from stage shows to advanced missile research.
And as for the army, Vollersten was stunned when he got inside one of their hospitals.
"They had everything you can imagine," he says. "Newest ECG, ultra scan, X-ray apertures."
None of it is shared with those in the countryside.
To help the reclusive North, South Korea launched what it calls the Sunshine Policy, including economic aid. But if the North's elite is siphoning that money off, then those who need a ray of hope first -- the weak, the starving and the young -- will likely get help last.
"There is a need for change, and then I have to do something," Vollersten says. "And the first thing I wanted to do is inform the world."
Vollersten is a German who remembers his nation's dark past of Nazi concentration camps and those who did not speak out.
Touring one hospital, he points to some patients.
"Like those children you can find at Dachau or Auschwitz," he says.
He came to do good in a place of heartache and despair. But when he spoke out, the North Koreans kicked him out.
Now he lives a personal nightmare, knowing perhaps more than any other foreigner who's been inside North Korea, that the conditions need not be.
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