Patients presenting with identical conditions can be up to 21 times more likely to be given certain treatments depending on where they live and in some cases the interventions may not be warranted, according to a biennial report on healthcare variation.
The Australian Atlas of Healthcare Variation reveals Sydney's eastern suburbs are the national capital of lumbar spinal decompression procedures and Hawkesbury residents have one of the highest rates of appendix removal in the western world.
Meanwhile, Hurstville women are eight times more likely to sustain a third or fourth degree perineal tear during labour and Richmond women are four times more likely to get a hysterectomy than those living in Dubbo.
The report is the second produced by the Australian Commission on Safety and Quality in Healthcare Agency on variations in procedures between different geographic areas.
Some of the variations can be put down to doctor awareness or the availability of different treatment options, some to differing opinions between specialists and some to the higher rate of certain conditions in different parts of Australia.
The commission's senior medical advisor, Anne Duggan, said some variation showed the system was working as it should, because the health system should respond to the needs and preferences of people in different areas.
But the size of the differences suggested some may not be warranted.
Professor Duggan said: "What we're trying to do is put the data out there to stimulate the experts to say, 'If we've got quite marked variations in rates, what's going on?'
"Is there clarity about who needs these surgical procedures or not, because if not where do we go next?"
For example, there was a seven-fold difference between the highest and lowest rates of hysterectomy, and a 21-fold difference between the highest and lowest rates of endometrial ablation.
This suggested women with heavy menstrual bleeding were not being offered new hormonal treatments, which are less invasive than surgery.
Australia has one of the highest rates for hysterectomy in the Organisation for Economic Co-operation and Development [OECD].
"The commission is working on a clinical standard with the colleges to make sure women are aware of their options," Professor Duggan said.
There was also a five-fold difference in the number of people being given lumbar spinal decompression in some areas compared with others, and more than 80 per cent of patients who were receiving the treatment had private health insurance.
The procedure, which is used to treat degenerative narrowing of the spinal column, was most likely to be given to people living in Sydney's eastern suburbs and north and Camden, while remote parts of Australia -& such as Far North Queensland and Alice Springs - had the lowest rates.
The report said the variation could be due to access to alternatives such as physiotherapy, patient preference and the decisions of individual clinicians.
"It is not possible to state how much of the observed variation in lumbar decompression surgery is unwarranted," the report said.
"The pattern of higher rates of operation with higher socioeconomic status, and the differences in rates between publicly and privately funded patients suggest that patients' ability to pay is a significant factor."
The rate of appendix removal varied by 3.5 times between the highest and lowest areas. Studies show the procedure could be unnecessary in up to one in four cases.
Some hospitals might be more likely to diagnose appendicitis through ultrasound or prescribe antibiotics for uncomplicated cases, the report found, and some would have greater capacity to put patients with suspected cases under prolonged observation.
The report also examined variation in caesarean rates for first time mothers aged 20 to 34 with uncomplicated pregnancies, as Australia has the 11th highest rate of 32 OECD countries.
It found the region with the highest caesarean rate had three times more operations than the area with the lowest, and women in private health funds were 1.4 times more likely to have them.
Also in childbirth, women in some areas were 11.8 times more likely to have third or fourth degree perineal tearing, which involves damage to the sphincter.
Royal Australian and New Zealand College of Obstetricians and Gynaecologists councillor Bernadette White said some of this variation could be due to reporting differences, as it was not clear-cut what constituted a second or third degree tear.
But hospital policies on the use of instruments, for example, could also play a part.
"It does seem like an enormously big difference," Dr White said.
"Some hospitals seem to have a much higher rate and I think when you've got these big outliers, you probably need to look at what you're doing."
