MRI and CT - the Curse of Incidentalomas

In 2001, 225 leading general internists were asked to rank 30 medical innovations in terms of their importance for patient care (see Health Affairs article here). By a large margin the group judged magnetic resonance imaging (MRI) and computed tomography (CT) scanning to be the most important. For physicians like me who entered medicine before the new imaging techniques were developed, the information MRI and CT provide seems miraculous!

But as physicians know all-too-well and as an excellent New York Times article by Gina Kolata today describes especially clearly - as scans rapidly improve, the frequency of "incidentalomas" increases just as fast.

Incidentalomas are scan findings that get labeled "abnormal" but actually have no clinical significance and are not causing a problem for the patient. The Kolata article describes Cheryl Weinstein, a healthy 64 year old with knee pain. Here's her story:

When she started looking up her symptoms on the Internet, she decided she probably had a meniscus tear. “I was very forceful in asking for an M.R.I.,” she said.

And when the scan showed that her meniscus was torn, she went to a surgeon expecting an operation.

He X-rayed her knee and told her she had arthritis. Then, Mrs. Weinstein said, the surgeon looked at her and said, “Let me get this straight. Are you here for a knee replacement?”

She said no, of course not. She skis, she does aerobics, she was nowhere near ready for something so drastic.

Then the surgeon told her that there was no point in repairing her meniscus because that was not her problem. And if he repaired the cartilage, her arthritic bones would just grind it down again.

For now, Mrs. Weinstein says she is finished with her medical odyssey.

Luckily the surgeon Mrs. Weinstein saw knew that cartilage tears are as common in people with arthritis of the knee who have no pain as they are for people with knee arthritis who do have pain. Otherwise she might have had an unnecessary operation. She would have risked complications for no potential upside gain. And all of those whose funds created the insurance pool that paid for the surgery would have wasted money.

The situation is much the same with herniated discs. Kolata reports on research demonstrating that routine scans for back pain do not improve outcomes. And the large number of "false positives" (scans interpreted as abnormal where the "abnormal" findings are not causing a problem) create psychological distress for the patients and may lead to unnecessary and potentially harmful tests and procedures.

MRI and CT are spectacular medical advances, but like everything in medicine they have potentially negative side effects. A substantial number of scans done in the U.S. should not be done. (Estimates vary, but all the estimates I've seen are more than 10%.) Unnecessary scans cause clinical and economic harm. Gina Kolata's article can be useful in public education - to help us better understand the limits of technology and the need to tolerate uncertainty.