It will no doubt be a slow road to recovery, but an African pancake tortoise is on the mend after a life-saving operation.

Polly the tortoise, who measures only 5.5in from tip to tail, had an egg-sized stone removed from her bladder in an hour-long operation.

Vets at Bristol Zoo were shocked to discover the 1.5in by 1.2in stone during a routine checkup.

If it had been left it would have caused the reptile to suffer a slow, painful death from renal failure.

Vets made the unusual decision to operate on Polly after x-rays showed she was weeks from death.

She was sedated and a hole was cut from the bottom of her carapace to remove the 19g stone. The piece of shell was then glued back into place. Five-year-old Polly is now being nursed back to full health in the zoo's Reptile House.

The zoo's head of veterinary services, Sharon Redrobe, said: "We x-rayed the tortoise as part of a standard health check and were amazed when we saw the size of the bladder stone.

"Anaesthetising a tortoise is quite tricky and requires specialist training, but she is likely to have been in some discomfort, so we took the decision to remove the stone as soon as possible.

"I've performed bladder stone operations on tortoises before, but never on a pancake tortoise and never with a bladder stone this big. Despite initial concerns that we might not be able to get the bladder stone out of the hole we made in the shell, the operation went very well and there were no complications."

African pancake tortoises are classed as a vulnerable species by the International Union for Conservation of Nature and Natural Resources.

They are most commonly found in Tanzania and Kenya and are named so because of their smooth, flattened pancake-shaped shell.

It was a bad week for tortoises after two were stolen from a house in Longwell Green, Bristol.

The tortoises are two years old and one of them has only one eye. They were taken on Friday, October 3.

Police are concerned that they may be offered for sale locally and are asking anybody with any information to contact Staple Hill police on 0845 456 7000 or call Crimestoppers on 0800 555 111.