When we think about private equity, we often think about companies like Toys R Us: purchased with borrowed money, loaded up with debt that ultimately all but destroys the firm. The investors make out, the employees and consumers lose out. But there’s another model too: Buy into a business where you can suck money out of consumers.

That describes the health-care business. And Sen. Elizabeth Warren (D-Mass.) has something to say about that.

The Post can exclusively reveal that earlier this week, Warren, along with Rep. Lloyd Doggett (D-Tex.) and Rep. Mark Pocan (D-Wis.), sent letters to five private equity firms — Enhanced Equity Funds, Welsh, Carson, Anderson & Stowe, the Blackstone Group, KKR and American Securities — asking them to provide her office not just with a list of all the health-care companies they’ve invested in over the past decade, but revenue earned from both in- and out-of-network billing.

Over the past decade and a half, private equity firms have aggressively upped their presence in the health-care industrial complex. They’ve invested in ambulance transportation, anesthesiology, radiology, emergency room staffing services and so on. Heck, they’re even in companies offering legally required in-hospital newborn hearing tests. The companies often do quite well financially: Priority Ambulance, backed by Enhanced Equity Funds, earned a spot on Inc. magazine’s most recent annual list of fastest-growing privately owned companies thanks, in part, to 248 percent revenue growth over a three-year period.

As private equity investment in the health-care sector ballooned, something else happened: The number of and balance on out-of-network medical bills soared. A study published in JAMA Internal Medicine this past summer found more than 40 percent of Americans who merely sought treatment at a hospital in their insurer’s network still received a bill from a provider not enrolled in their plan. The typical charge in such a case was $628, triple the amount in 2010. For someone actually admitted to a hospital, this sort of surprise charge came to more than $2,000 in 2016, double the amount in 2010. At the same time, the research revealed an incredible 85 percent of ambulance trips resulted in an out-of-network medical bill. Little wonder more people worry more about being able to pay an unexpected health-care expense than they do about their insurance premiums or deductibles, not to mention prescription drug costs.

These are not, as a rule, discretionary medical expenses, and they rarely occur in any predictable fashion. These surprise medical bills give lie to the idea that patients — people who are ill or injured! — can go shopping for medical services. Pro tip: Half of medical care in the United States occurs in emergency rooms. What’s a patient supposed to do when the ambulance company or a doctor in the hospital turns out to be out-of-network? Get up and find another ambulance or head to another medical institution?

There are no empowered consumers in this scenario. Instead, there are the financial vultures of private equity and their human prey.

The results are a bonanza for Wall Street but financially devastating for all too many Americans. Surveys show only 4 in 10 Americans have $1,000 set aside in savings, which makes these bills essentially unaffordable for many. But that doesn’t matter to our modern financial wizards, not when there’s gold in them thar illness!

“There’s no equity for patients receiving emergency care from a provider bought by private equity intent on exploitation,” Doggett said in an emailed statement. (Warren, Doggett and Pocan are not the first to reach out to private equity companies with pointed questions about their medical investments. Last month, Rep. Frank Pallone Jr. (D-N.J.) and Rep. Greg Walden (R-Ore.) contacted a number of private equity companies also seeking information, including asking if they have any influence over the billing practices of the medical companies they invest in.)

But this brings me to a bigger point: Legislation cracking down on surprise billing exists in both the House and the Senate. Yet even as there is bipartisan support for action, the outlook is uncertain. That’s in large part because several medical practices backed by private equity giants the Blackstone Group and KKR provided the funding for an ad campaign claiming the federal legislation would make it harder to receive medical care in an emergency. This is a ridiculous claim, but it caused fear on Capitol Hill.

The knock on Warren — at least as far as her critics go — is that she’s more about naming and demonizing the bad guys than raising Americans up. This is unfair. These letters are a follow-up to legislation Warren introduced this summer taking on the private equity business. The surge by private equity into the health-care business is one of the reasons so many of us say the United States is on the wrong track. They inject uncertainty into our financial existence, leaving us with little in the way of protection or recourse. Doing something about it means calling out the companies involved in the situation. Think of it as an emergency.

Read more: