A woman's decision to take an 11-week-old kitten to an RSPCA hospital facility for treatment after it became ill ended in heartbreak, with the kitten being euthanased without consent.

Key points: Belinda Stevens said the RSPCA Wacol hospital thought she was a foster carer and euthanased her son's cat

Belinda Stevens said the RSPCA Wacol hospital thought she was a foster carer and euthanased her son's cat Ms Stevens said by the time she was told the cat was being put to sleep it was too late

Ms Stevens said by the time she was told the cat was being put to sleep it was too late RSPCA Qld said the organisation would be reviewing its communication processes

Brisbane mother Belinda Stevens told ABC Radio Brisbane's Mornings program the family's kitten, Marshmallow, was euthanased at the RSPCA's Wacol facility due to a misunderstanding about its ownership.

"Well, I was at work and my son came down with Marshmallow, who was a bit unsteady on her feet," Ms Stevens told Rebecca Levingston.

"The kids were a bit worried because they hadn't seen her like that before, but she had been like that before and made a full recovery.

"So I'd taken her down to the Wacol RSPCA, obviously to see what was wrong with her."

Warning: This story contains an image that some readers may find disturbing.

Ms Stevens said after stating her name and address to the receptionist, within minutes the vet informed her they had to "put Marshmallow to sleep".

"I didn't even have probably two minutes and the vet came back out," she said.

"I was thinking OK … they've obviously had to sedate her because they have to check her out, and I asked if I could go and see her out the back, and they said no, you have to go to the consultation rooms.

"And I was like what … as soon as I walked into the room and opened the door there was Marshmallow, dead.

"I just broke down in tears, my son broke down in tears. Instead of seeking help we ended up bringing back a dead kitten."

Ms Stevens said there was confusion about whether she was the cat's owner or a foster carer.

"The vet actually turned around and she said, aren't you the foster carers? And I'm like, what?" she said.

"She says, 'I thought you were the foster carers', and I said, 'no, this is my cat and you killed my cat'.

"Nobody really spoke to me after that, except for me grabbing my cat and walking out. It took me about half an hour in their reception area to get names and stuff so I could formally make a complaint.

"They say to me in phone calls that they definitely stuffed up.

"The only thing they're offering at the moment is free cremation or a free adoption later on down the track."

Ms Stevens said Marshmellow was euthanased by RSPCA vets without consent. ( Supplied )

'It's our fault': RSPCA Qld

RSPCA Queensland spokesman Michael Beatty said the RSPCA believed it was necessary to put Marshmallow down but conceded there was a communication issue.

"I can totally understand that Belinda is heartbroken. There's no doubt about it," Mr Beatty said.

"Basically what happened is, is our veterinary hospital at Wacol is not a public veterinary clinic. It is only for RSPCA animals.

"We really wish it could be a public clinic, but sadly we don't have the funds, so it is purely for RSPCA animals."

Mr Beatty confirmed the confusion stemmed from a mistaken assumption that Ms Stevens was a foster carer and that Marshmallow was a foster kitten.

"When Belinda brought Marshmallow in, the veterinary staff mistakenly assumed that Marshmallow was a foster kitten," he said.

"Certainly, she should have been consulted, but it was presumed that she was a foster carer."

Mr Beatty said based on the severity of Marshmallow's condition, euthanasia was the only humane option.

"To be honest, even if she was a foster carer and Marshmallow was a foster kitten, probably it should have been communicated to her that Marshmallow was going to be euthanased," he said.

"All we can do, and we have done so, we've personally rung her and said how sorry we actually are.

"Undoubtedly in terms of the communication it's out fault — we should have checked to see if she was a foster carer.

"But in terms of Marshmallow needing to be put to sleep, we believe that any other vet would have done exactly the same thing."

Mr Beatty confirmed the RSPCA would be reviewing its communication processes following the incident.

"We're not just reviewing but making certain that something like that never happens again," he said.

"All I can say is, we're sorry."

Boy 'not coping well'

Ms Stevens said what she wanted was to have been consulted on the health of her cat before any further treatment decisions were made.

"They said in order for them to treat Marshmallow I would need to surrender her, and I had not signed any paperwork. No verbal, no written permission, no ID was shown and they went ahead and euthanased her," she said.

"I didn't get an explanation until after the fact. They already had euthanased her — that's when I got an explanation that she had diabetes, apparently, and they didn't have the facilities to treat her and basically ended up killing her."

She said her son was "not coping well" after the incident.

Ms Stevens said if she had been consulted prior to the action being taken, she may have considered consenting to euthanasia.

"If I had been informed, possibly. She had been like that once before and she recovered fully by the next day, but I had no explanation of what had happened or what was wrong with her," she said.

On whether she would take up the RSPCA's offer of free adoption, Ms Stevens said she was too distraught by the experience to consider it.

"I can't, not after this. Not after this. It's like taking away a family member. She was a family member," she said.

"With the cremation, every time I'm going to be thinking, here's Marshmallow … this is what I've got to look at every day, an urn. Because they killed her, and it's a reminder of what they've actually done. I can't do that."