WASHINGTON — Roughly one in every six times someone is taken to an emergency room or checks in to the hospital, the treatment is followed by a “surprise” medical bill, according to a study released Thursday. And depending on where you live, the odds can be much higher.

The report from the nonpartisan Kaiser Family Foundation finds that millions of people with what’s considered solid coverage from large employers are nonetheless exposed to “out-of-network” charges that can amount to thousands of dollars. It comes as congressional lawmakers of both parties and the Trump administration move to close the loophole, with a Senate panel scheduled to vote on legislation next week.

A patient’s odds of getting a surprise bill vary greatly depending on the state he or she lives in. Texas seems like a bit of a gamble, with 27 percent of emergency room visits and 38 percent of in-network hospital stays triggering at least one such bill. Minnesota looks safer, with odds of 2 percent and 3 percent, respectively.

Researcher Karen Pollitz of the Kaiser Foundation said the reasons for such wide differences are not entirely clear, but seem to be related to the breadth of hospital and doctor networks in each state, and the ways those networks are designed.

Patients in New York, Florida, New Jersey and Kansas were also more likely to get surprise bills. Among the other states where it was less likely were South Dakota, Nebraska, Maine and Mississippi.

Averaging the results nationwide, 18 percent of emergency room visits and 16 percent of stays at an in-network hospital triggered a surprise bill for patients with health insurance through a large employer, the study estimated.

That illustrates the need for Congress to get involved, said Pollitz, since large-employer plans are regulated by federal law and surprise billing protections already enacted by states like New York do not apply to them.

“This is a prominent problem affecting patients, and it is beyond the reach of state laws to fix, and it is by definition beyond the ability of patients to fix on their own,” she said.

Next Wednesday, the Senate Health, Education, Labor and Pensions committee plans to vote on bipartisan legislation that would limit what patients can be charged to their in-network deductibles and copays. The bill from Sens. Lamar Alexander, R-Tenn., and Patty Murray, D-Wash., would require insurers to pay out-of-network doctors and hospitals the median — or midpoint — rate paid to in-network providers. The House Energy and Commerce committee is working on similar legislation. President Donald Trump has said he wants to sign a bill.