Liam, 16, has a rare and incurable disease called type four Ehlers-Danlos Syndrome (EDS). He lives with an open wound in his stomach and two colostomy bags, but that weekend the bags had ruptured.

"I thought, we're not going to be able to survive the night, I just needed my son to get to the hospital," Mrs Parr said.

She called triple-zero, but the person on the other end of the phone told her Liam's condition was not "life-threatening" enough for an ambulance.

"He said 'we can't get out there, it's going to be a very long, long, long time,'" Mrs Parr said.

"He said 'you take him; if you think it's urgent, you take him.' I wouldn't be ringing the ambulance if it's not urgent. It was a kick in the guts."

She contacted Liam's surgeon, who told her to wrap him in glad wrap so that he could get into the car.

If faeces had leaked from the colostomy bags into his open wound, Mrs Parr said an infection could have been fatal.

Liam's stress alone could have brought on a heart attack, she said. She said sufferers of type four usually "don't survive" heart attacks, as it is the vascular form of EDS.

"With what he's got, there's no cure and it is life-threatening. For him (the operator) to say it's not life-threatening, it was very heartbreaking," Mrs Parr said.

The Parr family live in Eden Park, and on that Sunday - Mother's Day - it took Mrs Parr one hour and 20 minutes to get her son to the Royal Children's Hospital.

He was admitted into emergency and underwent surgery later that evening, but his skin was infected by the broken colostomy bags and he remained at the hospital on Wednesday.

Liam was diagnosed with type four EDS, an incurable tissue disorder, which can cause arterial, digestive and uterine complications, in September last year.

Mrs Parr said she rarely used an ambulance, but every other interaction she'd had with paramedics and ambulance drivers in the past had been "fantastic."

Her worry is that the people in the call centre taking those life-and-death calls do not have enough skill to deal with these situations.

"Next time I ring them I'll be a bit more wary of them, and you don't want that; you want to be able to call them for help," she said.

"They've got to have something in the system from hospitals to say 'this is urgent - this child has been in hospital, they've got a disease'. Anything to say when they've got an ambulance in the area, [that] they'll send someone there.

"These people on the phone need to be extremely patient and each person they speak to is very different."

Ambulance Victoria's executive director emergency operations Mick Stephenson said he had made contact with the Parr family to discuss the case and apologise.

He said a thorough review would be conducted.

"A preliminary review of the case has indicated that an ambulance should have been dispatched and would have been had we correctly investigated the patient's medical history," he said.

"Unfortunately, this wasn't the case and we are extremely sorry for the distress that the patient and family has endured.

"We will be conducting a thorough internal review to ensure that this does not happen again."

The incident comes as Ambulance Victoria response times appear to be improving. The latest quarterly figures show statewide code-one (lights and sirens) responses had improved by 4.1 per cent since December.

Ambulance response times in the City of Whittlesea, which includes Eden Park, have been reduced by about one minute since 2015, according to Ambulance Victoria's January to March 2017 response times report.

Code-two response times - acute and time-sensitive, but not requiring a lights-and-sirens response - are now almost five minutes quicker than in December last year.