1. US for Kidney Stones is Safe and Effective

Practice Change: In patients I suspect of having renal colic, an US will be my first imagining study.   I can always get a CT later if I’m not satisfied with the workup. I may talk to the patients about possible need for further imaging if we don’t have a diagnosis, but if 2/3 patients avoid a CT scan, that is a win.

Ultrasonography versus Computed Tomography for Suspected Nephrolithiasis

— NEJM from Sept 2014



Population: Prospective Randomized PRAGMATIC trial of patients aged 18 – 76 with abdominal or flank pain that was presumed to be due to kidney stone by the treating ED physician.

** Patients thought to be at risk for other serious intra-abdominal pathology like appendicitis, AAA, bowel disorder were excluded.

**Pregnant patients excluded


 Intervention: Randomization to 3 groups

  1. Bedside US by the ED physician (EDUS)
  2. Radiology US (RUS)
  3. CT scan per local protocol (CT)

This is a “pragmatic trial” in that just the INITIAL imaging study (CT vs US) was randomized. All other care was left up to the treating physician, including the possibility of obtaining a CT scan later in the patient’s ED stay if their initial imaging was randomized to an US and the clinician felt it was indicated.

 Control: The CT group

Primary Outcomes:

A. Were there missed diagnoses with complications?

B. Amount of Radiation within 6 mos of randomization.

Secondary Outcomes:

  1. Follow up at 3,7, 30, 90, and 180 days, lots of data points


Results: 2759 patients randomized equally to the three groups.

  • 41% with h/o nephrolithiasis
  • 52% with CVA Tenderness
  • 63% with hematuria 

Primary Outcomes:

          A. Missed Diagnoses at 30 days:

11 (0.4%) Total Missed Diagnoses 

  • NO significant difference between groups: (0.7% EDUS, 0.3%RUS, 0.2% CT)

         B. Radiation in 6 months :

Less radiation in both US groups (10.1mSv EDUS, 9.3mSv (RUS), 17.1mSv (CT) p<.0001

We all know radiation is bad, but how bad is it? 

www.xrayrisk.com estimates your lifetime risk of cancer from radiation

SO, For a 25 yo F with a typical 14 mSv abdominal/pelvis CT, the additional lifetime risk of cancer rises by 1/452.

Secondary Outcomes

  1. No difference in diagnostic accuracy between the three groups for nephrolithiasis  — 84-86% Sens, 50-53% Spec for all three groups.
  2. 27% of patients in RUS, 41% in EDUS group got a CT scan on initial visit
    1. (So only about 1/3 total got any CT scans at initial ED visit)
  3. NO difference in serious adverse events or missed diagnoses between groups.

Conclusions: This study demonstrates that a plan of initial evaluation of a possible kidney stone with US provides the benefit of decreasing radiation exposure for patients without risking any more missed diagnoses or adverse events. 

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