A South Australian doctor has performed a historic operation on a Cambodian man who's entire mouth had been closed over with a huge growth emanating from his lip.

Eng Kheng, a resident in a remote village in the country's Kampong Cham province, has been living with the condition for 30 years and had never received dental treatment.

Dr Andrew Cheng, an Adelaide-based doctor, heard about Mr Kheng's incredible case through a charity he works with in Cambodia, and wanted to help.

'I've never see anything like this before. I don't think anyone around the world has seen anything that big,' Dr Cheng told Daily Mail Australia. Mr Kheng was originally being looked at by doctors for cataracts, before shocked doctors noticed the growth in his mouth.

They alerted Dr Cheng, who flew with his mentor to Mr Kheng's village after being sent medical information from Cambodian clinicians. 'The local doctors and surgeons organised CT scans to make sure it wasn't a malignancy. We managed to utilise all the CT scans in the photos to plan the surgery in Australia.'

The size of the growth from his gums was the result of a rare condition called Gingival Hyperplasia. There is a one in 750,000 chance of being diagnosed with the condition according to Dr Cheng. 

Mr Kheng was forced to adapt his eating and swallowing, only being able to consume certain foods.

'He usually only had fluids, cooked rice, noodles and soup. And lemonade, he loves lemonade,' Dr Cheng told Daily Mail Australia.

'He was able to swallow but the way he swallowed was different to you or I. He kinks his neck back and swallows, a bit like a bird.'

His airwaves have experienced a degree of narrowing but fortunately Mr Kheng never had any issues breathing, despite dealing with the condition for 30 years.