SPCA Otago animal attendant Maartje Hyink said the 3-year-old cat was found in Moana Cres, Musselburgh, earlier this year with a collar around its stomach.
The smell of rotting flesh was ''putrid''. Scars on the animal revealed the collar had originally been put on the cat too loosely, she said.
''She's got her paws through.''
The buckle on the red cotton collar had corroded into the flesh, she said.
A cat owner should be able to put three fingers under a cat collar; any more and it was too loose.
A safety collar, featuring elastic and a snap release, was preferable, as a cat could free itself if a collar became hooked on something.
A Mosgiel vet estimated the collar had been around the cat's belly for six weeks.
Ms Hyink said a magnet - for a cat door - on the collar had attracted nails and screws, which had pierced the skin.
The cat was not microchipped but had been desexed and was domesticated.
After the owner failed to come forward, the cat was named Moana, after the street where it was found.
The animal had socialised well with both cats and dogs and was available for adoption.
