Doctors had to either use a hacksaw and Swiss army knife to amputate a trapped man's legs or leave him to die.

After five hours of crawling through the pancaked Pyne Gould Corporation building on Tuesday, Dr Stuart Philip, 38, came across another survivor. But this time, the rubble could not be lifted and the man's trapped lower legs had to be cut off.

"There really wasn't any other option. Essentially the procedure was performed with a Swiss army knife. A builder arrived with a hacksaw. I know that sounds terrible, but that's all we had, " the Brisbane-based urologist said yesterday.

Another urologist performed the operation as she could squeeze in next to the man. She was traumatised and had since travelled back to Australia, he said.

An anesthetist was on hand to administer pain relief, but not enough to dull the agony.

Dr Philip last saw the 52-year-old man, known only as Brian, when he left him at Christchurch Hospital after performing CPR in the ambulance. He heard yesterday that the man was recovering in Waikato Hospital with his family.

"It was the most fantastic news."

But not everyone was lucky.

"My first job was actually climbing up into the top of the building where there was an Australian guy trapped. He subsequently died, we couldn't get him out."

The crew had saved about a dozen people by nightfall.

At one point, Dr Philip texted his wife Emma to say goodbye. The couple have two children, a son Sam, 5, and daughter Hannah, 3.

"At one stage when we were having aftershocks and the rubble was falling, we weren't sure if we were going to make it out alive. [My wife] sent me a terse text message telling me to get out of the building."

But he just could not leave.

Dr Philip, formerly of Hastings, studied in Christchurch and is a urological surgeon in Brisbane. He was at the annual Urological Society of Australia and New Zealand meeting with 250 doctors and 150 nurses.

Many helped treat casualties after the quake.