Kidney Stone canstockphoto19503829Are you getting a CT or bedside ultrasound as your first-line diagnostic approach to patients with undifferentiated abdominal or flank pain in whom you suspect kidney stones? In a landmark 15-center, multidisciplinary study published in the New England Journal of Medicine in September 2014, Dr. Rebecca Smith-Bindman (UCSF Department of Radiology) and her research team looked at exactly this question for emergency department patients. In the paper, “Ultrasonography versus CT for suspected nephrolithiasis,” Dr. Smith-Bindman and Dr. Ralph Wang (UCSF Department of Emergency Medicine) kindly joined us on a quick discussion about her paper.

Bottom Line

Start with the bedside ultrasound to evaluate patients with suspected kidney stones. According to this large multicenter trial, about 2 out of every 3 patients will NOT need a CT scan.

Article citation

Smith-Bindman R, Aubin C, Bailitz J, Bengiamin RN, Camargo CA Jr, Corbo J, Dean AJ, Goldstein RB, Griffey RT, Jay GD, Kang TL, Kriesel DR, Ma OJ, Mallin M, Manson W, Melnikow J, Miglioretti DL, Miller SK, Mills LD, Miner JR, Moghadassi M, Noble VE, Press GM, Stoller ML, Valencia VE, Wang J, Wang RC, Cummings SR. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl  J Med. 2014 Sep 18;371(12):1100-10. DOI. PMID: 25229916.

[su_spoiler title=”Timestamps” style=”fancy” icon=”caret”]
  • 00:00 Introduction to article
  • 01:40 Q1: About 1/3 of patients in the ultrasound study arms eventually went on to get CT’s in the same ED stay. What would you recommend to clinicians about when that should be? The STONE score was mentioned.
  • 08:30 Q2: Can you address generalizability issues in this 15-center study whereby the cohort has 40% with a history of previous kidney stones and only 60% demonstrating microscopic hematuria. Also what are your recommendations for obese patients (men >280 lb, women >250 lb) who were excluded from your study? CT them all?
  • 16:45 Q3: What has been the feedback from urologists since the paper was published? What are the drivers of CT ordering? See the #UroJC journal club summary by nephologist Dr. Joel Topf.
  • 23:10 Q4: What’s next? What’s NOT in your paper?
[/su_spoiler] [su_box title=”Abstract” style=”soft” box_color=”#1a80b6″ title_color=”#000000″ radius=”5″]

Background: There is a lack of consensus about whether the initial imaging method for patients with suspected nephrolithiasis should be computed tomography (CT) or ultrasonography.

Methods: In this multicenter, pragmatic, comparative effectiveness trial, we randomly assigned patients 18 to 76 years of age who presented to the emergency department with suspected nephrolithiasis to undergo initial diagnostic ultrasonography performed by an emergency physician (point-of-care ultrasonography), ultrasonography performed by a radiologist (radiology ultrasonography), or abdominal CT. Subsequent management, including additional imaging, was at the discretion of the physician. We compared the three groups with respect to the 30-day incidence of high-risk diagnoses with complications that could be related to missed or delayed diagnosis and the 6-month cumulative radiation exposure. Secondary outcomes were serious adverse events, related serious adverse events (deemed attributable to study participation), pain (assessed on an 11-point visual-analogue scale, with higher scores indicating more severe pain), return emergency department visits, hospitalizations, and diagnostic accuracy.

Results: A total of 2759 patients underwent randomization: 908 to point-of-care ultrasonography, 893 to radiology ultrasonography, and 958 to CT. The incidence of high-risk diagnoses with complications in the first 30 days was low (0.4%) and did not vary according to imaging method. The mean 6-month cumulative radiation exposure was significantly lower in the ultrasonography groups than in the CT group (P<0.001). Serious adverse events occurred in 12.4% of the patients assigned to point-of-care ultrasonography, 10.8% of those assigned to radiology ultrasonography, and 11.2% of those assigned to CT (P=0.50). Related adverse events were infrequent (incidence, 0.4%) and similar across groups. By 7 days, the average pain score was 2.0 in each group (P=0.84). Return emergency department visits, hospitalizations, and diagnostic accuracy did not differ significantly among the groups.

Conclusions: Initial ultrasonography was associated with lower cumulative radiation exposure than initial CT, without significant differences in high-risk diagnoses with complications, serious adverse events, pain scores, return emergency department visits, or hospitalizations. (Funded by the Agency for Healthcare Research and Quality.) study registration record


Summary by American Journal of Kidney Diseases (AJKD) blog

A great summary was written by Dr. Swapnil Hiremath at the AJKD blog breaking down the details of the study.

Other great analyses discussing the paper

(c) Can Stock Photo

Michelle Lin, MD
ALiEM Founder and CEO
Professor and Digital Innovation Lab Director
Department of Emergency Medicine
University of California, San Francisco
Michelle Lin, MD


Professor of Emerg Med at UCSF-Zuckerberg SF General. ALiEM Founder @aliemteam #PostitPearls at Bio:
Michelle Lin, MD