Medical Scans: A Reality Check


By Mary Carpenter

THE FILM Oppenheimer has once again raised questions about radiation exposure—both during testing of the bombs in 1940s New Mexico, and, more widely relevant today with medical scanning. Issues surrounding medical scans include how often and how much of the body to scan safely—but more often, at what point scans are necessary at all. Notably, common conditions like UTIs and constipation are usually benign but, especially if occurring repeatedly or changing suddenly, can be signs of more serious problems.

“To keep medical radiation exposure to a minimum, ask if the results of a scan or test are likely to change the course of your treatment. If not, it may not be necessary,” writes Florida Mayo Clinic radiologist Patricia Mergo. But Mergo asserts: “there’s no reason to forgo a [well-advised] imaging test or X-ray-assisted procedure…especially true for older adults, as potential radiation-caused cancer development may not occur for decades.”

“The potential for an increased risk of cancer due to medical exams using radiation is small,” she notes. And today’s CT and PET scanners “use a much lower radiation dose than was used even just a few years ago.” Also, compared to whole-body scans, radiation doses are now lower when adjusted for body size and used for specific diagnoses.

“Incidentalomas” and “cascade of care,” however, are terms that have come into recent use to describe pitfalls of unnecessary or “low-value” scans. Incidentalomas refer to the likelihood of a benign finding that can set off a “cascade” of further tests that often include further scans, which in turn detect more incidentalomas.

“Low-value” scans and services refer to those with little to no benefit—and sometimes with potential for harm. Common low-value scan examples are chest-x-rays performed in a pre-surgical work-up, MRIs done early for uncomplicated low-back pain, and most notably, an array of head-CT scans—such as on patients with signs of concussion, “even though CT does not help diagnose concussion but rather other risks of bleeding,” according to Yale ER physician Edward Melnick.

“One in every three CT scans performed on patients with minor head injury is not medically necessary,” according to research by Melnick and colleagues. “Nonclinical factors” leading to unnecessary scans included lack of confidence and experience on the part of doctors; and “empathetic themes,” such as the ability of doctors to listen and care, and of patients to trust medical advice—in particular that advising against a scan.

In Emergency Departments (ED), the “use of imaging has increased disproportionate to the number of visits,” according to 2018 Johns Hopkins research. Between 1996 and 2007, ED visits increased nationwide by 30% but the numbers of scans increased by 330%—while MRI use tripled between 2001 and 2010. “Consistently associated with ED overuse” were severity of injuries and “older patient age.”

For constipation-related complaints, a Swiss study of 1,997 patients found that “most indications for [abdominal x-rays] did not comply with guidelines, and elderly women appeared particularly at risk of being exposed to inappropriate examination.” Importantly, these scans “did not prevent the need for additional examinations.”

Constipation varies widely among individuals; is dependent on diet, activity and hydration; and “is about much more than how many times you go in a day or a week,” warns Cedars-Sinai gastroenterologist Christopher Almario. “Genetics may play a role in chronic constipation as well as how quickly one’s intestines naturally move.” While an abrupt change in bowel movements can suggest a serious problem, the two common complaints, straining and hardness of stools, usually improve with changes in diet and physical activity levels.

“It’s fine to take a gentle laxative every day or on a regular basis,” writes Almario. On the other hand, according to UCSFhealth, “most people who are mildly constipated do not need laxatives and an overuse of laxatives can actually cause constipation [but] they may be recommended for those who are still suffering from the condition even after making diet and lifestyle changes.”

Urinary tract infections—with incidence rising by age, to affect 15 to 20% of women ages 65 to 70 — can cause inflammation anywhere in the urinary tract: in the bladder, called cystitis; and in the kidneys, pyelonephritis. For those with repeated UTIs, physicians can recommend scans to check for unusual physical structures—such as a congenital “duplex” or double-collecting kidney, which has two ureters draining urine from a single kidney.

“Treatment is rarely needed,” according to the Cleveland Clinic website. But because potentially more serious issues can arise when UTIs occur in those with rare problems—such as obstructions that block outflow of urine from the bladder—scans can provide the relief of an explanation and sometimes suggest surgical options.

The dangers of radiation from anywhere —medical scans, bomb testing and myriad other sources —continue to provoke heated arguments with most involving comparisons to background radiation exposure. According to the National Cancer Institute, “Most cancers that have occurred or will occur among the 1945 residents of New Mexico are likely to be cancers unrelated to exposures from Trinity fallout.”

But radiation levels following Trinity, according to a 2010 CDC study, “reached almost 10,000 times what is currently allowed in public areas,” writes Tina Cordova in a New York Times op-ed. “For days after [the test], ash fell from the sky contaminated with 10 pounds of plutonium…has had devastating health consequences…families in New Mexico with four and five generations of cancer since the bomb was detonated.”

Years ago my internist recommended I have a full-body CT scan—for small but invisible amounts of blood in the urine—the kind of scan usually restricted to people with existing cancer diagnoses. After that scan turned up something so small it was undoubtedly insignificant, my doctor continued recommending “follow-up” scans for four more years until I switched doctors.

I had worried because whole-body scans have the highest level of scan radiation, 12 millisieverts (mSv), while targeted scans have closer to 7-8 mSv; bone scans involve closer to 4 mSv, and single x-rays have the lowest at .1 mSv. But reading Patricia Mergo’s reassurance about low radiation levels and slow-growing cancers helped both to reassure me and to convince me most likely to say yes to future scans—from my new doctor.


—Mary Carpenter regularly reports on topical subjects in health and medicine.


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