My pager emits the same urgent beep no matter the occasion. That afternoon, it was the local preoperative clinic to say my 80-something patient, Lily, had been given an electrocardiogram (EKG) “just to be safe” before a minor office procedure.

The EKG was a little off, the page went on. Could I take a look? Lily (I’m identifying her by only her first name at her request) felt fine. No chest pain. No trouble breathing. But now that the irregularity was out there, the procedure would be delayed until we had answers.

Flash forward one borderline blood test result, several phone calls between myself, Lily, and the anesthesiologist, 14 emails, an office visit, and a completely normal stress test. Lily (and her heart) were in no better health, yet she was slightly less well off and more than slightly distressed by all the trouble she went through. I was disappointed that I’d failed her.

And this was a relatively good outcome.

“If You Give a Mouse a Cookie,” Laura Numeroff’s classic children’s book, is a cautionary tale about the downstream consequences of a single, seemingly innocuous decision. You gave the mouse the cookie. Naturally, he wanted a glass of milk to go with it. Before long, the mouse was moving in and sharing your ­Netflix password.

This pattern is familiar to many of us, whether as doctors or as patients: A medical test spurs a “cascade” of phone calls, office visits, tests and treatments, each a logical, even inevitable, progression from the one before.

In a sense, this is how medical testing is supposed to work. But no test is perfect and every test has trade-offs — including false positives and incidental findings (results you weren’t looking for and are often better off not knowing). Some tests (like Lily’s) we even know to be low-value — meaning they have at best minimal benefit in a given situation.

And so the harms from a cascade — such as cost, time, stress, pain from unnecessary biopsies, and overdiagnosis — can outweigh any benefits, especially when the cascade stems from an unexpected finding or when that initial test wasn’t needed in the first place.

Researchers and policymakers point to low-value medical services as a major source of U.S. health-care spending bloat — by a new estimate, up to $101.2 billion a year. Remarkably, this estimate does not even include the cost of cascades (my research team and others are working to fill that gap).

Our team started by looking at national Medicare bills for one of the most common procedures among older adults: cataract surgery. Studies clearly show that for most patients, preoperative tests such as EKGs don’t improve health or reduce complications from the low-risk, 20-minute procedure. Yet nearly a quarter of these cataract surgery patients still receive these low-value, preoperative EKGs each year.

For every 100 patients who got this EKG, we counted up to 11 extra tests, treatments, office visits, new diagnoses or hospitalizations in the following three months alone.

Those extra cascade services cost 10 times that of the initial EKG — for a total of $38 million in one year across the United States. (Did some of these extra services help some of the patients who got them? No doubt. But others were most certainly harmed and on average, we know it was at best a wash.)

In another study using a cancer database linked to Medicare bills, Yale University researchers found that older men received the no-longer-routinely-advised prostate-specific antigen (PSA) tests for prostate cancer screening at a national cost of almost $450 million per year. Nearly three-fourths of this bill came from downstream biopsies and related complications.

Of course, financial costs are only part of the issue.

One of my colleagues no longer remembers what prompted that first CT scan of his patient’s abdomen years ago, but he cannot forget what happened next. The scan showed an unexpected small, ill-defined mass abutting her kidney. A follow-up MRI and then a painful biopsy were just as ambiguous. So surgeons removed the mass — and the kidney with it — only to discover it was a harmless piece of fat. The devastating conclusion: Her remaining kidney failed soon after.

When our team surveyed doctors across the United States about cascades from incidental findings, we discovered how common such stories were.

All but two of the nearly 400 generalists who responded to the survey had seen such cascades as physicians, and most had even had them as patients or as patients’ family members. Follow-up phone calls, repeated tests and office visits after incidental findings were commonplace. Most doctors had seen cascades lead to invasive tests, emergency department visits and hospitalizations.

The majority told us that cascades cause harm to their patients — including psychological, financial and physical — at least several times a year. The doctors were also affected themselves. Most had experienced wasted time and effort, frustration or anxiety from cascades (possible precursors to burnout) — especially doctors who practiced in rural areas.

Cascades are common because incidental findings are common. With widespread screening (including notoriously low-value, head-to-toe scans) and improvements in technology, laboratory and imaging tests are increasingly likely to pick up small abnormalities that are most often inconsequential. And once that result is there, it is hard to look away.

For some of these findings, doctors don’t have research to guide us on how often it might cause problems, or on what to do next. Even when we have this information, we are often swayed to do more (after all, doctors are selected and trained to be thorough, to find The Answer.

When we posed a hypothetical scenario about following up a lung nodule, most doctors in our survey said they’d ignore evidence-based guidelines that recommend no more testing if the radiology report said to do it. Reflecting on their most recent real-life cascade, nearly half of doctors who did more testing to follow up an incidental finding did not think it was medically needed. Instead, they felt they were following the norms of the medical community or shielding against a potential lawsuit.

Doctors and patients alike are also swayed by our cognitive biases — like that one time in a thousand when that tiny speck turned out to be cancer and has haunted us ever since. Even though “nothing” cascades are far more common, we may brush these off as happy near-misses.

When I talked to Lily after her stress test came back normal, she told me (and I wanted to believe) that part of her felt relief alongside the regret.

Public education efforts — such as the Choosing Wisely campaign — are trying to persuade doctors and patients to avoid low-value tests in the first place (in our survey, doctors said one-third of their most recent cascades may have started this way).

What’s becoming clear is that we also need better ways to navigate cascades once they begin — to maximize any upside and minimize the harm. For patients, that means understanding tests come with trade-offs. For doctors, it’s setting expectations about what tests might reveal, framing results for what they are, and working with patients to decide the next steps informed by evidence and patient preferences.

To extend the analogy past its breaking point: Often, you should just say no to the cookie. Other times, call it quits after the glass of milk. And be prepared, every so often, to add another profile to your Netflix account.

Ishani Ganguli is an assistant professor of medicine at Harvard Medical School and an internist at Brigham and Women’s Hospital.