Kirsten Thain’s 13-year-old twin boys had the same imaging scan nine months apart after spraining their knees playing soccer.

But the bills Thain had to pay for her sons’ MRIs — magnetic resonance imaging used to detect abnormalities — were dramatically different.

Thain’s first son had the test done at Hawaii PET Imaging in August 2014 for $1,433. Thain’s portion was $59.93. The second brother had an MRI in May at Kapiolani Medical Center for Women & Children for $1,984, but the out-of-pocket cost for Thain was roughly five times higher at $317.12.

"I was just outraged. It’s the same procedure," said the single mother of four, who lives in Kahaluu. "Had I had this procedure done elsewhere, even at another hospital, the bill would have been one-fourth the cost. It just made me feel cheated."

Thain’s case illustrates the difficulty patients face in purchasing medical services that vary widely in price within Hawaii and nationwide.

When Thain called her health insurer, Hawaii Medical Service Association, to find out the reason for the disparity in costs, she was told that even though the services were the same, the facilities had different contracts with HMSA.

"There’s a breakdown in the system in the way that we do things that is to the detriment of the patient," Thain said. "The cost is hidden from the patient until after service is rendered. Even if you are astute enough to try to see what it’s going to cost ahead of time, you can’t. A $300 bill might be peanuts to somebody else, but I’m a single parent and that’s a lot of money."

Stephen Kemble, past president of the physicians’ advocacy group Hawaii Medical Association, said hospitals "always charge a lot more for the same services" than an independent private practice would because of higher overhead.

"An independent practice has a lower overhead, so it ends up they can get away with charging more for the same procedure because it’s done out of the hospital," he said. "There’s no quality difference; it’s purely a matter of what they can get away with charging. It’s not a real market at all. Usually you’re not in a position to shop around."

HMSA acknowledged the problem members face not knowing the price of services beforehand. The state’s largest health insurer said it is building an online tool to make pricing more transparent. The goal is to help members determine whether a service is a benefit of their plan and give them a range of how much they can expect to pay out of pocket, thereby allowing them to shop around.

"We believe that cost is an important factor when making health care decisions," HMSA spokeswoman Elisa Yadao said in a statement. "Members can use this tool when discussing their options with their doctor. Our goal is to increase transparency and help our members make better, more informed decisions about their physical, emotional, and financial well-being."

HMSA didn’t say when the tool will be available to members. The insurer has been trying to get doctors to discuss prices with patients, but the move has riled physicians.

Earlier this year HMA, the physicians association, objected to a new contract with the insurer that required doctors for the first time to discuss possible higher out-of-pocket costs with patients referred to specialists outside HMSA’s provider network. HMA doctors say HMSA is trying to discourage them from referring patients to nonparticipating providers, even though they may be deemed best for the patient’s care.

The state also is working to get price transparency for consumers. It was awarded more than $3 million in federal grants last year to develop the Hawaii Health Data Center to analyze claims data and eventually be a resource for consumers to compare prices.

"Once we’re up and running, we intend to have a consumer facing website. We’ve got until 2017 to get it running," said Bryan Fitzgerald, a representative for the state Office of Information Management and Technology.

The Centers for Medicare and Medicaid Services, the federal agency in charge of Medicare, for the first time in 2013 released a list of prices U.S. hospitals charge for common procedures. The list exposed extreme differences in the pricing of medical services. For instance, treating a patient with a brain hemorrhage at Kaiser Permanente Hawaii costs $30,000, while the price for the same procedure 7 miles away at Straub Clinic & Hospital was 80 percent higher at $54,000. A CMS spokeswoman said fiscal 2014 data won’t be available until next year.

"We can’t make the decisions we need to make to avoid this kind of mess because there’s no menu," Thain said. "You have to tell people your pricing. You can’t just serve them a meal and then tell them it’s $400. People would be furious. They would refuse to pay. Nobody does that, because it’s bad business, so why is it happening with medical services? You just get the bill and you’re flabbergasted."