Ultrasound Equal To CT As First Test For Kidney Stone Diagnosis

Rebecca Smith-Bindman, MD Professor in the Departments of Radiology; Epidemiology and Biostatistics; and Obstetrics, Gynecology and Reproductive Medicine UCSF San Francisco Calif.MedicalResearch.com Interview with:
Rebecca Smith-Bindman, MD
Professor in the Departments of Radiology;
Epidemiology and Biostatistics; and Obstetrics, Gynecology and Reproductive Medicine UCSF San Francisco Calif.

Medical Research: What are the main findings of the study?

Dr. Smith-Bindman: New technology is rapidly developed in medicine, and its important to understand how that technology should be used to improve patient health outcomes. Sometimes the technology is far better than existing technology and it should replace the earlier technology, and sometimes it is not and therefore should not be used. In this clinical scenario – I e. patients who present to an emergency department with abdomen or back pain thought to possibly reflect kidney stones, ultrasound is a simpler, less expensive , and more readily available test in the emergency department setting and therefore if it is equal to CT with respect to patient outcomes, it should be used as the first test in these patients. Currently, CT is the test widely used for patients with suspected kidney stones.

We assessed a large number of patients with suspected kidney stones seen at one of 15 large academic emergency medicine departments across the country. Patients were assigned to point of care ultrasound performed by an ED physician, radiology ultrasound or radiology CT. We assessed a broad range of patient centered outcomes and found each of the three tests we studied were equivalent in terms of these outcomes including complications related to missed diagnoses, related serious adverse events, time spent in the emergency department and repeated ED visits and hospitalizations. However, the exposure to ionizing radiation was around half as high in patients who underwent ultrasound as their first test, and thus ultrasound should be used as the first imaging test in patients with suspected nephrolithiasis.

Medical Research: Were any of the findings unexpected?

Dr. Smith-Bindman: This is the first large comparative effectiveness studies focused on diagnostic imaging in the ED setting where we randomized patients to different tets, and then followed patients for a relatively long period of time (6 months) to compare outcomes – i.e. what happened to patients, related to what test they first underwent. Our study was successful in many ways including our ability to recruit a large number of patients, and to learn what happened to our patients with relatively little loss to follow up.  This is the first study to directly compare ultrasound and CT and the results were surprising. In summary, even though CT scanning was slightly more sensitive for detection o stones, this did not translate into any improvements in patient outcomes. Further, physicians could identify the patients that needed secondary testing, as when we compared patients assigned to each of the three arms,  the accuracy was the same. Thus the results strongly suggest that ultrasound should be used as the first test in patients with suspected nephrolithiasis as it results in half the radiation exposure, without any important differences in any other patient outcomes.

Medical Research: What should clinicians and patients take away from your report?

Dr. Smith-Bindman: Patients with suspected kidney stones should undergo ultrasound when they are evaluated in the ED if the treating physician believes kidney stones is the most likely diagnosis or if they believe they need imaging to exclude a diagnosis of kidney stones. Additional imaging can be obtained at the discretion of the treating physician if they feel it is necessary. This reflects a change in clinical practice where currently CT scan is the most used test in this setting.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Smith-Bindman: The next steps in this research for us is to try to disseminate the results broadly so that clinical practice changes. I believe if a qualified physician is available to perform ultrasound, than patients with suspected kidney stones should undergo ultrasound as the first imaging test.


Ultrasonography versus Computed Tomography for Suspected Nephrolithiasis

Rebecca Smith-Bindman, M.D., Chandra Aubin, M.D., R.D.M.S., John Bailitz, M.D., Rimon N. Bengiamin, M.D., R.D.M.S., Carlos A. Camargo, Jr., M.D., Dr.P.H., Jill Corbo, M.D., R.D.M.S., Anthony J. Dean, M.D., Ruth B. Goldstein, M.D., Richard T. Griffey, M.D., M.P.H., Gregory D. Jay, M.D., Ph.D., Tarina L. Kang, M.D., Dana R. Kriesel, M.P.H., M.S., O. John Ma, M.D., Michael Mallin, M.D., William Manson, M.D., Joy Melnikow, M.D., M.P.H., Diana L. Miglioretti, Ph.D., Sara K. Miller, M.D., R.D.M.S., Lisa D. Mills, M.D., James R. Miner, M.D., Michelle Moghadassi, M.P.H., Vicki E. Noble, M.D., Gregory M. Press, M.D., Marshall L. Stoller, M.D., Victoria E. Valencia, M.P.H., Jessica Wang, M.D., Ralph C. Wang, M.D., and Steven R. Cummings, M.D.

N Engl J Med 2014; 371:1100-1110
September 18, 2014DOI: 10.1056/NEJMoa1404446