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
- Bedside US by the ED physician (EDUS)
- Radiology US (RUS)
- 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
A. Were there missed diagnoses with complications?
B. Amount of Radiation within 6 mos of randomization.
- 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
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.
- No difference in diagnostic accuracy between the three groups for nephrolithiasis — 84-86% Sens, 50-53% Spec for all three groups.
- 27% of patients in RUS, 41% in EDUS group got a CT scan on initial visit
- (So only about 1/3 total got any CT scans at initial ED visit)
- 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.