A British doctor volunteering in DR Congo used text message instructions from a colleague to perform a life-saving amputation on a boy.
Vascular surgeon David Nott helped the 16-year-old while working 24-hour shifts with medical charity Medecins Sans Frontieres (MSF) in Rutshuru.
The boy's left arm had been ripped off and was badly infected and gangrenous.
Mr Nott, 52, had never performed the operation but followed instructions from a colleague who had.
The surgeon, who is based at Charing Cross Hospital in west London, said: "He was dying. He had about two or three days to live when I saw him."
The boy had been bitten by a hippo, the Daily Mail reports.
Mr Nott knew he needed to perform a forequarter amputation, which requires the surgeon to remove the collar bone and shoulder blade.
He contacted a colleague who had performed the operation before.
"I texted him and he texted back step by step instructions on how to do it," he said.
"Even then I had to think long and hard about whether it was right to leave a young boy with only one arm in the middle of this fighting.
"But in the end he would have died without it so I took a deep breath and followed the instructions to the letter.
"I knew exactly what my colleague meant because we have operated together many times."
The surgeon had just one pint of blood and an elementary operating theatre, but the operation, performed in October, was a success and the teenager made a full recovery.
Mr Nott, who volunteers with MSF for a month every year, said: "It was just luck that I was there and could do it.
"I don't think that someone that wasn't a vascular surgeon would have been able to deal with the large blood vessels involved. That is why I volunteer myself so often, I love being able to save someone's life."