EBQ:Ultrasound versus Computed Tomography for Suspected Nephrolithiasis

incomplete Journal Club Article
Smith-Bindman, R., Aubin, C., Bailitz, J., Bengiamin, R.N., Camargo, C.A. Jr., Corbo, J. et al,. "Ultrasonography versus Computed Tomography for Suspected Nephrolithiasis". New England Journal of Medicine. 2014. (371):1100–1110.
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Clinical Question

What is the initial imaging method for patients with suspected nephrolithiasis presenting to the emergency room?


  • Ultrasound is less sensitive than CT for the diagnosis of nephrolithiasis, but can be used as an initial test for patients with suspected nephrolithiasis
  • Ultrasound first as the initial imaging method can result in
    • no CT for the most patients,
    • lower cumulative radiation exposure
    • no significant difference in the risk of subsequent serious adverse events (e.g. pain scores, return ED visits, hospitalizations)

Major Points

Ultrasound either point-of-care or radiology was associated with a lower cumulative radiation exposure than CT without significant differences in high-risk diagnoses, serious adverse events, pain scores, return emergency department visits, hospitalizations or diagnostic accuracy in patients 18-76 years old presenting to the emergency department with suspected nephrolithiasis.

Study Design

  • Multicenter, pragmatic, comparative effectiveness trial
    • 3638 patients were screened
    • 3100 eligible
    • 2759 patients (89% of eligible patients) underwent randomization with 908 in the point of care ultrasound, 893 to radiology ultrasound and 958 to CT scan
  • No significant difference in three groups with respect to gender, age, race, self=report pain score or hospital admission after being seen in the ED
  • Past medical history of kidney stones, cancer, diabetes and hypertensioin were not significantly different across the three groups.
  • Of note,
    • 41.6% had history of kidney stones
    • 63.3% had hematuria
    • 52.5% had costovertebral- angle tenderness
  • Physical exam findings of costoverbetral angle tenderness , right lower quadrant tenderness, left lower quadrant tenderness, murphy’s signs, McBurney’s sign, guarding as well as physicians estimated likelihood of kidney stones were obtained for the three groups with no significant difference.
  • Patients were contacted at 3, 7, 30, 90 and 180 days to assess study outcomes


18 to 76 years old who presented to the emergency department with suspected nephrolithiasis who presented to the Emergency room in one of the 12 emergency departments

Patient Demographics

Inclusion Criteria

18-76 years of age who reported flank or abdominal pain with ED physician who was planning to order imaging to establish or rule out primary diagnosis of kidney stones

Exclusion Criteria

  • Patients who the ED physician deemed were at high risk for alternative diagnoses including acute cholecystitis, appendicitis, aortic aneurysm, or bowel disorders
  • Pregnant women
  • Men more than 129 kg
  • Women more than 113 kg
  • Single kidney
  • History of renal transplant
  • Undergoing dialysis


Initial imaging based on randomization with point-of- care ultrasound examinations performed by ED physicians who had training as recommended by ACEP, radiology ultrasound performed in radiology department per guidelines and CT performed according to local standards.


Primary Outcome

  • 30 day incidence of high risk diagnoses (abdominal aortic aneurysm with rupture, pneumonia with sepsis, appendicitis with rupture, diverticulitisi with abscess or sepsis, bowel ischemia or perforation, renal infarction, renal stone with abscess, pyelonephritis with urospesis or bacteremia, ovarian torsion with necrosis or aortic dissection with ischemia) with complications that could be related to missed or delayed diagnosis
  • 6 month cumulative radiation exposure (calculated by amount of radiation per CT scan as well as reviewing medical records to see if patient had any repeat radiation exams)

Secondary Outcomes

  • Serious adverse events (death, life-threatening, required hospitalization, caused persistent or clinically significant diability or required medical, surgical or other intervention to prevent permanent impairment ) 16
  • Related serious adverse events –three people analyzed all 466 serious adverse events and rated each on as definitely, probably, possibly related, unlikely to be related, or not related to initial randomization
  • Pain (11 point Visual Analogue Scale)
  • Return emergency department visits
  • Hospitalizations
  • Diagnostic accuracy (compared diagnostics to either patient’s personal observation of stone passage or surgically removed)

Subgroup analysis

  • Ultrasound has lower sensitivity with greater specificity than CT.
  • POC US (Sensitivity, Specificity) (54%, 71%)
  • Radiology US (Sensitivity, Specificity) (57%, 73%)
  • CT scan (Sensitivity, Specificity) (88%, 58%)

Criticisms & Further Discussion

  • No statistical difference based on imaging method for the incidence of high risk diagnosis or related adverse events was low at 0.4% and did not vary based on imaging method
  • The ultrasound group had statistically significantly lower mean 6 month cumulative radiation exposure compared to the CT group
  • No statistical difference in serious adverse events in all three groups (12.4% of the point of care ultrasound, 10.8% in radiology ultrasound, 11.2% in CT)
  • No statistical difference in the average pain score, return emergency department visits, hospitalizations and diagnostic accuracy in all three groups
  • Patients in the ultrasonography groups were more likely that those in the CT group to have additional diagnostic testing during the emergency department visit with 40.7 % of the point of care ultrasound group and 27.0% of the radiology ultrasound group to have a CT scan performed. Only 5.1% of the CT group underwent ultrasound.
  • Investigators, patients and physicians were not blinded to the study group assignments
  • Diagnosis of stone is a very strict definition which was unbiased but some participants might foreget that they passed a stone

Point of care ultrasound was performed by emergency physicians that have had training and certification in ultrasound and this might not be present in all emergency rooms

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