TUESDAY, Feb. 11, 2020 (HealthDay News) -- You scheduled your surgery and made sure both your doctor and hospital are in your insurer's approved network of providers. Everything went without a hitch -- until a whopper of a bill showed up in the mail for "out-of-network" care during your operation.

The average out-of-network surprise bill tops $2,000, a new study finds. And about 20% of patients who had surgery using a doctor and hospital considered in-network for their insurance got a surprise bill.

So, what gives? In some cases, surprise bills are for medical imaging during surgery or for assistants that patients didn't even know would be involved.

"In this study, we narrowed it down to those cases where patients did as well as they could checking to make sure the surgeon and hospital were in-network, and still one in five got an out-of-network bill," said the study's lead author, Dr. Karan Chhabra of the University of Michigan Institute for Healthcare Policy and Innovation in Ann Arbor.

He said 37% of the surprise bills came from out-of-network surgical assistants. Another 37% came from anesthesiologists. The average out-of-network surgical assistant bill was more than $3,600; anesthesiologist bills topped $1,200.

The findings were published Feb. 11 in the Journal of the American Medical Association.

Some people might consider the $2,000 average surprise bill a big deal. But NPR reported last June that a 26-year-old woman was hit with a $94,000 surprise bill after surgery to remove a tumor from her spinal cord. Her insurer said it would cover only $816.

The bill was for neuromonitoring services during the operation. Neuromonitoring tracks nerve health during such a delicate procedure to make sure no damage is being done. The patient had no idea that any part of her surgery would be billed at out-of-network fees. More than two years later, her billing dispute remains unresolved.

Although the new study found that the average surprise bill was much lower than that woman faced, the unexpected $2,000 comes on top of nearly $1,800 in out-of-pocket outlays for deductibles and co-insurance.

The study reviewed claims from a large insurance company from both in-network and out-of-network providers. The claims stemmed from care of nearly 350,000 adults under age 65. All had one of seven common procedures, including knee repair, gallbladder removal and heart bypass surgery.

Where you live seems to matter. Your odds of getting an out-of-network bill are much higher in Alaska than in Nebraska -- 46% versus 3%, the study found. Folks in the South and Northwest were also more likely to be hit with surprise bills. People in the Midwest had a low risk of getting one.

Dr. Karen Joynt Maddox wrote an editorial that accompanied the findings. She's co-director of the Center for Health Economics and Policy, at Washington University School of Medicine in St. Louis.

"This study really pointed out that surprise billing is much more common than people have thought," Joynt Maddox said.

What's really frustrating, she said, is that this issue doesn't lead to better health care, only to higher costs. And it's not a problem patients can solve themselves.

"This is an example where consumer-driven health care is failing the patients," Joynt Maddox said.

Chhabra said while it's important to ask your doctor, hospital and insurer if everyone is in-network, "it's really unfair to ask patients to do all of the work."

Both experts said surgeons have some control over who is in the operating room, particularly surgical assistants. So doctors can make sure their assistants are in a patient's network. But surgeons often don't have a say in who the anesthesiologist will be.

Joynt Maddox expressed concern that individual doctors may run into some of the same issues individual patients do when trying to get assurances that a provider is in-network. She suggested that a group of doctors might have better luck.

"Collectively, doctors need to step up and advocate for their patients. Clinicians need to get together and say this isn't right for our patients and it's not acceptable. We have to end this practice," Joynt Maddox said.

There has been some legislative movement, but no definitive solutions yet. Chhabra and his colleagues noted that four federal bills were introduced last year. And, this year two bills have been introduced in the U.S. House of Representatives, he said.

Both experts, however, mentioned concerns about pushback and lobbying by physician groups backed by private-equity firms. Those groups have suggested that proposed legislation might lead to a loss of their rate-negotiating power, Joynt Maddox wrote in her editorial.

"Until policymakers and clinicians come together on this, patients need to ask questions: 'Will there be any out-of-network people involved in my surgery?'" she said.

Chhabra said patients must act as their own advocates.

"And, be sure to get everything in writing because network status can change," he advised. "Double-check with your insurance company and your doctor. And, if this is an issue that concerns you, write to your congressional representative and ask them to support legislation to end surprise billing."

More information

Learn what steps you can take to try to prevent surprise billing with this advice from AARP.