Ultrasound Is Better than CT for Kidney Stones

Despite the increased use of CT scans to diagnose kidney stones for emergency department patients, the imaging technology is no better than an ultrasound exam, and ultrasound is safer.

Ultrasound, according to a recent study published in the New England Journal of Medicine, (NEJM) is the preferred first-line diagnostic tool when someone presents at the ER with the extreme pain characteristic of kidney stones. It was clear that although ER physicians routinely turn to CT scans for kidney stone diagnosis, “Ultrasound is the right place to start,” concluded the study’s senior author, Dr. Rebecca Smith-Bindman. She’s a professor at UC San Francisco.

The issue, as readers of this blog will recognize, is radiation. CT scans expose patients to significant amounts of radiation; ultrasound scans don’t.

In addition, ultrasound isn’t as expensive as CT. Those two realities make Smith-Bindman’s case compelling: “Radiation exposure is avoided, without any increase in any category of adverse events, and with no increase in cost.”

Usually, a CT exam is conducted by a radiologist. An ultrasound exam can be done by a sonographer (ultrasound technician), physician or radiologist.

If the ultrasound isn’t sufficient, patients can always follow up, at their physician’s discretion, with a CT scan. That technology renders a three-dimensional image by coordinating a series of X-rays taken from multiple angles.

As noted on ScienceDaily.com, according to a National Health and Nutrition Examination Survey in 2010, 1 in 11 people reported having had at least one kidney stone. And the use of a CT scan to diagnose them has increased by a factor of 10 in the last 15 years.

In the NEJM study, conducted at 15 medical centers, emergency room patients whose pain was suspected to be due to kidney stones were randomly assigned to one of three imaging groups. People in one group received an ultrasound exam performed by an emergency room physician onsite. People in another group received similar ultrasonography performed by a radiologist, who is a specialist in the procedure. People in another group received an abdominal CT scan, also conducted by a radiologist.

With six months of patient follow-up, ScienceDaily reported, the health outcomes for 2,759 patients were just as good with ultrasound as with a CT scan. Patients fared no worse when emergency physicians instead of radiologists performed the ultrasound exam. Serious adverse events, pain, return trips to the emergency department and hospitalizations did not differ significantly among groups.

As we wrote in our earlier blog, this is another episode in the if-you-build-it-they-will-come (and pay) story of medical technology being written by hospital emergency rooms. So if this scenario describes your situation, and the doctor wants to do a CT scan first, question it. Ask why an ultrasound is not the first choice, and if you don’t get a reasonable answer, decline the CT in favor of the ultrasound.

To learn more about kidney stones, see our blog, “Treating Kidney Stones Often Has Complications.”

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