Effect of an Ultrasound-First Clinical Decision (CD) Tool in Emergency Department Patients with Suspected Nephrolithiasis: A Randomized Trial

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Effect of an Ultrasound-First Clinical Decision Tool in Emergency Department Patients with Suspected Nephrolithiasis: A Randomized Trial

Source: Am J Emerg Med 60 (2022) 164–170


More than two million annual visits to emergency departments (EDs) in the United States are for patients with suspected nephrolithiasis. The most common imaging test for suspected nephrolithiasis in the ED is computed tomography (CT) scan of the abdomen and pelvis. However, increased CT use has not resulted in increased rates of kidney stone diagnosis, hospitalization, or diagnosis of important alternative diagnoses and is associated with radiation exposure and an increased risk of cancer. In addition, experts have estimated that radiation exposure from diagnostic radiology may result in 3–5% of all future malignancies.

Ultrasonography (US) of the urinary tract could potentially replace the increasing use of CT scans. However, there have been no randomized studies to determine the efficacy of a clinical decision support (CDS) tool to promote an US-first strategy for suspected nephrolithiasis.

The authors sought to assess whether CDS deployed at the time a CT scan was ordered for suspected nephrolithiasis would impact CT use, radiation dose, ED revisits, and total cost in a randomized trial. They hypothesized that the randomization to the US-first CDS tool would decrease CT use and radiation exposure in patients with suspected nephrolithiasis, without increasing ED revisits or cost.


Study design and setting

This was a pragmatic randomized trial to assess the impact of a clinical decision support tool at a single academic medical center ED where ultrasound is frequently used to evaluate patients with suspected nephrolithiasis.

Study participants

Physicians, nurse practitioners, and physician assistants working in the ED were included in this study.

Patients were included in the study when their providers ordered a CT scan of the abdomen/pelvis for a patient with suspected nephrolithiasis (as defined as a reason for exam matching the following terms: “stone”, “renal”, “hydro”, “nephro” “flank pain” and “calculi”).

Provider orders were excluded when patients were < 18 or > 75 years old; those who had already received an US during that visit; past history of kidney transplant, solitary kidney, or end stage renal disease; weight > 285 lbs in men or > 250 lbs in women; and temperature > 100.4 F. These criteria were adapted from the STONE trial.


Randomization (1:1) was conducted on the patient level, where providers caring for patients randomized to the intervention group received the US-first CDS for CT orders meeting study inclusion criteria.

Since most of the ED providers could not identify patients in whom ultrasonography was appropriate, the authors developed CDS tool embedded in the electronic health record (EHR) and triggered when a CT scan order was placed for a reason for exam of suspected nephrolithiasis. The CDS tool prompted the provider to consider ordering an ultrasound first if the following with appropriateness criteria for ultrasonography were met:

  1. No age and weight exclusion criteria
  2. Low risk of stone emergency (i.e., obstructing stone with sepsis, renal deterioration, intractable symptoms, or solitary kidney/end stage renal disease/prior kidney transplant)
  3. Low risk of an alternative diagnoses (e.g., appendicitis, ovarian torsion, aortic aneurysm)

If all criteria were met, the CDS tool prompted the provider to remove the CT order and replace it with an US order. The provider was given the choice to order a point of care ultrasound (POCUS) or a radiology performed ultrasound. If the provider did not change their order, they were asked to acknowledge the reason that they did not accept the decision support advice. Possible choices included “moderate to high risk of stone emergency”, “moderate to high risk of alternative diagnosis”, “test recommended by another provider”, “weight > 285 lbs in a man or > 250 in a woman”, “test not for kidney stone”, or “age < 18 > 75”.


The main outcome of the study was the proportion of patients who received any CT scan of the abdomen and pelvis as part of the ED visit. Secondary outcomes included radiation dose in millisieverts, ED return visit (within 3, 7, and 30 days), and ED return visits during which repeat CT scans were obtained or inpatient hospitalization occurred.


Between January 2, 2019, and Dec 19, 2019, 583 ED patients received a CT scan of the abdomen/pelvis with a reason for exam including suspected kidney stone. 329 were excluded, leaving 254 patients were eligible and enrolled in the study.

The US-First CDS tool was shown for 128 patients and was not shown for 126 patients. The mean age was 52 years old (± 14 years), 124/254 (48.8%) of patients were female, and 128/254 (50.4%) were white.

CT completion at the index ED visit differed significantly by study arm. CT scan completion in the CDS arm was 111/128 (86.7%) compared with 119/126 (94.4%) in the usual care arm (risk difference: −7.7%).

Of the CT scans completed at the index visit in the CDS arm, 41/128 (32.0%) were without contrast vs. 58/126 (46.0%) in the usual care arm.

Total radiation exposure did not differ by arm; mean radiation dose in CDS arm 6.8 millisieverts) versus 6.1 millisieverts in the usual care arm.

CT scans during ED revisits at 30 days did not differ significantly between the CDS and usual care arms: 8/128 (6.1%) vs. 12/126 (9.5%), with a risk difference of −3.4% (95% CI -10.0 to 3.1%).

While CT use was lower, US use was higher in the CDS arm: 23/128 (18.0%) of participants received ultrasound, versus 15/ 126 (11.9%) in the usual care arm.

Those receiving the CDS tool did not experience a statistically significant increase in ED revisits. At 7 days, there was no statistical difference in ED revisits in the CDS arm (5/128 [3.9%]) versus the usual care arm (12/126 [9.5%]), absolute risk difference of −5.6% (−11.7 to 0.6%).

Similarly, at 30 days, ED revisits were no different in the CDS arm (16/128 [12.5%]) versus 25/126 [19.8%] in the usual care arm, absolute risk difference − 7.3%.

The cost of care did not differ significantly between study arms. The direct cost per encounter in the CDS arm was $4503 vs. $5082 in the usual care arm. Most of the costs reflected those who were admitted to the hospital.


The author concluded that implementation of the US-first CDS tool resulted in lower CT use for ED patients with suspected nephrolithiasis, and promoted US use without increasing costs, ED revisits, or additional CT scans performed during ED revisits.

The authors recommended to further explore these results in a multi-center study, which may ultimately improve the ED evaluation of a suspected nephrolithiasis.