Urban myth or unacknowledged elephant in the room? A consultant working in the x-ray department at a west Midlands hospital has said London zoo had to scan patients who were too obese for NHS equipment.

Travis, not his real name, speaking on Radio 5 Live's Your Call, talked about a patient who was suspected of having a potentially life-threatening clot on the lung "a couple of years ago" but was too heavy for screening. Instead a fellow consultant who had referred the woman to his department told him: "In which case, let's get an ambulance and we will send her to London Zoo."

Travis added: "I promise you. This is absolutely true. It is my understanding that she (his medical colleague) had had previous experience where patients who had acquired morbid obesity to such a level, they were sent to London zoo, where they have top veterinary medical facilities including special scanners that can take large animals like lions and small elephants and hippos etc".

He added: "I believe that they accept, on an intermittent basis, patients that have acquired a similar size."

The Guardian talked to Travis, who said he had had accounts of this happening "from two separate sources and have no reason to doubt it". The Royal College of Radiologists could not help as to whether such an instance has ever happened in Britain.

Doctors have raised this issue of inadequate provision before and have also on occasions warned they may have to call in zoos or vet schools, citing incidents in the US as a precedent. Such moves would surely lead to complaints that a veterinary solution was demeaning.

But zoos and vet schools, even if asked if they can help, say they can't. London zoo said: "We have never scanned obese people at ZSL London Zoo." Bristol, Chester and Edinburgh zoos also say it hasn't happened. Edinburgh says it doesn't have a large MRI scanner, just specially adapted mobile x-ray and ultrasound equipment that it can take to the animals.

Graham Milligan at the Royal Veterinary College in London, said: "There are no animal specific scanners (MRI or CT), they are all human scanners. It is possible for vet schools to adapt human scanners to take the weight of large animals, but not to increase the size of the scanner head, therefore scanning is limited to extremities (head, feet and lower limbs).

"This does not make them suitable for larger people, and there is a need in the health service for scanners that could take heavier patients (over 200kg). The RVC, like other schools, is not in a position to scan human patients and does not scan people."

So if it is an elephant in the room, it is very well camouflaged.