Ultrasound beats CT scan for initial imaging for kidney stones

Ultrasound is better, but CT scans are the norm for suspected kidney stones. Here’s a streamlined version of the American College of Physicians summary of a new study that backs this up.

The study included 2,759 patients who presented with suspected cases of kidney stone to 15 geographically diverse academic hospital EDs, 4 of which were “safety net” hospitals. Patients were randomized to 1 of 3 groups: point-of-care ultrasonography performed by an emergency physician, ultrasonography performed by a radiologist, or abdominal CT. […]

The study found a 0.4% rate (11 patients) of high-risk diagnoses with complications within 30 days, and this did not vary significantly by imaging method. […]

The mean 6-month cumulative radiation exposure was significantly lower in the ultrasonography groups than in the CT group (10.1 mSv and 9.3 mSv vs. 17.2 mSv;P<0.001). The radiation in the ultrasound groups resulted from some patients going on to have additional testing, some of which included CTs. Median length of stay in the ED was significantly longer in the radiology ultrasound group: 7.0 hours compared to 6.3 hours in the ED ultrasound group and 6.4 hours in the CT group (P<0.001 for radiology versus each of the other 1 groups). Return ED visits, hospitalizations, and diagnostic accuracy did not differ significantly among the groups. […] There was no significant difference in results between those with and those without complete follow-up.

The authors emphasized the results do not suggest that patients undergo only ultrasound imaging, but rather that ultrasonography should be used as the initial diagnostic imaging test, with further imaging studies performed at the discretion of the physician.

The study is here and an accompanying editorial is here. The next time I go to the ED with a suspected kidney stone—if there is a next time—I intend to bring both these papers with me, or pull up this post on my phone. A stone maker shouldn’t die of cancer induced by CT studies for treatment of stones. That would certainly not be “doing no harm.”


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