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What are the clinical effects of the different emergency department imaging options for suspected renal colic? A scoping review

Abstract Objectives Clinicians have minimal guidance regarding the clinical consequences of each radiologic imaging option for suspected renal colic in the emergency department (ED), particularly in relation to patient‐centered outcomes. In this scoping review, we sought to identify studies addressing the impact of imaging options on patient‐centered aspects of ED renal colic care to help clinicians engage in informed shared decision making. Specifically, we sought to answer questions regarding the effect of obtaining computed tomography (CT; compared with an ultrasound or delayed imaging) on safety outcomes, accuracy, prognosis, and cost (financial and length of stay [LOS]). Methods We conducted a comprehensive search using Pubmed, EMBASE, Web of Science conference proceedings index, and Google Scholar, identifying studies pertaining to renal colic, urolithiasis, and ureterolithiasis. In a prior qualitative study, stakeholders identified 14 key questions regarding renal colic care in the domains of safety, accuracy, prognosis, and cost. We systematically screened studies and reviewed the full text of articles based on their ability to address the 14 key questions. Results Our search yielded 2570 titles, and 68 met the inclusion criteria. Substantial evidence informed questions regarding test accuracy and radiation exposure, but less evidence was available regarding the effect of imaging modality on patient‐oriented outcomes such as cost and prognosis (admissions, ED revisits, and procedures). Reviewed studies demonstrated that both standard renal protocol CT and low‐dose CT are highly accurate, with ultrasound having lower accuracy. Several studies found that ureterolithiasis diagnosed by ultrasound was associated with overall reduced radiation exposure. Existing studies did not suggest choice of imaging influences prognosis. Several studies found no substantial differences in monetary cost, but LOS was found to be shorter if a diagnosis was made with point‐of‐care ultrasound. Conclusion There is a plethora of data related to imaging accuracy. However, there is minimal data regarding the effect of CT on many patient‐centered outcomes. Further research could improve the patient‐centeredness of ED care.

influences prognosis. Several studies found no substantial differences in monetary cost, but LOS was found to be shorter if a diagnosis was made with point-of-care ultrasound.
Conclusion: There is a plethora of data related to imaging accuracy. However, there is minimal data regarding the effect of CT on many patient-centered outcomes. Further research could improve the patient-centeredness of ED care.

K E Y W O R D S
computed tomography, kidney stones, patient-centered, renal colic, shared decision-making, ultrasound INTRODUCTION

Background
Every year, 1.6-2.1 million patients get a computed tomography (CT) scan in US emergency departments (EDs) for suspected ureterolithiasis. 1 The majority of these patients do not see a change in management based on their CT scan, and this has led to a continuing discussion regarding how to decrease radiation exposure in this population. 2 Ultrasound, both ED point-of-care ultrasound (POCUS) and radiology performed, is considered an acceptable and safe alternative to CT despite lower accuracy. 3 Because the decision between these 2 diagnostic modalities involves trade-offs, this clinical situation has been identified by the emergency medicine community as appropriate for shared decision making (SDM). 4

Importance
Considerations beyond accuracy are relevant to both patients and clinicians in SDM conversations about the decision to undergo CT scan for suspected ureterolithiasis. 7,8 Many questions may arise in these conversations, with each question being of variable importance to different patients and clinicians. A scoping review, which examines a broader array of literature and outcomes, is appropriate for examining the evidence and assessing what evidence is appropriate to include in decision making in this context. A scoping review provides a broader view of a complex topic rather than focusing on a narrow question.

Goals of this investigation
Drawing from a patient-centered and clinician-centered needs assessment, 8 we sought to examine the existing literature to explore what is known about the patient-centered consequences of the decision between ultrasound and CT scan.

METHODS
We applied the scoping review methodology of Arksey and O'Malley. 9 Per Arksey and O'Malley, we chose a scoping review to "map the extent, range, and nature of research activity," "summarize and disseminate findings," and "identify research gaps." Because we were looking at a broader range of research, we did not feel a narrow systematic review would be appropriate. 10

Identifying the research questions
As described in a related qualitative study creating a decision aid, we engaged 102 stakeholders, both clinicians and patients, through 10 focus groups and 30 interviews, to determine decisional needs. This included an exploration of which questions are commonly asked, by both clinicians and patients, regarding the decision to use CT or ultrasound for the diagnosis of ureterolithiasis. 8 Questions fell into several domains: safety (including risk of an incidental findings), accuracy, prognosis (changes in admissions, ED revisits, or procedure rates), and the cost (including time and financial) ( Table 1). Questions related to treatment (types of urologic procedures, the effects of α-blockers) were felt to be outside the scope of this review.

Identifying relevant studies
To identify all possibly relevant research articles, we developed a search strategy in consultation with a health research librarian (B.G.   Table 4 in Supplement B How accurate is ultrasound for the diagnosis of renal colic? Table 5 in Supplement B Can a stone be predicted by other factors without using CT? Table 6 in Supplement B Plan of care/prognosis Patient oriented: Will a CT change my chance of admission? Table 7 in Supplement B Will a CT change my chance of ED revisit? Table 8 in Supplement B Clinician centered: What is the chance the patient will need a procedure (and therefore should have a CT)? Patient oriented: Will getting a CT change my chance of needing a procedure? has been summarized and analyzed in systematic reviews and metaanalyses, we chose to exclude individual articles if they were included in a later systematic review or meta-analysis, but include the systematic reviews and meta-analyses for the questions of diagnostic accuracy. If those studies answered questions in other domains, they were included. We excluded articles in which the content focused on pediatrics, geriatrics, pain management, urologic/surgical treatment strategies, preventive strategies, epidemiologic data, stone formation, and basic science. We excluded abstracts if there was no associated article as we decided these abstracts did not contain sufficient information for inclusion or quality rating.

Screening
Two levels of screening took place using dedicated online article

Charting the data
A standardized abstraction form was created to abstract relevant data.
E.S. created the form, which was then reviewed with all data abstractors and revised as needed. The 3 authors abstracting the data (E.D., E.S., and S.D.) together piloted and modified the data abstraction form, discussing issues as they arose. Two authors (E.D., E.S., or S.D.) independently abstracted the data from each study. If the researcher felt the study met the inclusion criteria, the standardized data abstraction form was used to record relevant data, including author, title, journal, date, type of study, hypothesis, sample size, results of the study as they related to scoping review questions (Table 1), relevance to clinical scenario, and population comparability. If the tested hypothesis was a secondary outcome or secondary analysis, this was also noted.
The two authors abstracting the data also rated the studies using the National Heart, Lung, and Blood Institute quality assessment tools. 11 The 2 entries were then compared, discussed, and combined. At this point, studies rated poor quality by both reviewers were excluded. Disagreements were discussed with a third reviewer, who re-reviewed the article, until consensus was reached.

Collating and summarizing results
Studies were grouped by domains and questions. We discussed all domains of the relevant studies, returning to the abstraction file or original articles as needed, and summarized the data. Individual studies were included under multiple domains if they answered multiple study questions.

RESULTS
The initial search yielded 2570 citations ( Figure 1). After removing duplicates, we had 2404 citations. After dual screening and full-text review, we were left with 68 articles that met the inclusion criteria.
Our articles included 6 analyses of a single RCT and 2 analyses of a retrospective cohort, leaving us with 62 unique studies. Regarding quality, 36.8% were rated as "good," 20.6% as "good/fair," 36.8% as "fair," and 5.9% as "fair/poor." Data are summarized in Both Studies show significant heterogeneity. Higher quality studies suggest that with a low-risk patient population (younger, higher likelihood of kidney stone, lack of concerning symptoms), the risk of a dangerous alternative diagnosis is low (<2%) and is not necessarily affected by the use of CT.
What is my chance of having an incidental finding detected on CT?
Patient Limited data suggest incidental findings found on CT range from 7% to 29%, but no quantification of economic or emotional burden is suggested.

Accuracy
How accurate is the CT? What is the role of low-dose CT?
Both CT scan is the gold standard for the diagnosis of ureterolithiasis. Low-dose CT scan has high sensitivity and specificity for the diagnosis of ureterolithiasis.
How accurate is ultrasound? Both Ultrasound has moderate sensitivity and specificity. Moderate or greater hydronephrosis has high specificity.
Can a stone be predicted by other factors (prediction scores) without using CT?

Both
The most frequently evaluated scoring system for predicting ureterolithiasis is the STONE score. It risk stratifies patients regarding their likelihood of having a stone. External validation studies have had variable results, but the score may be useful for risk stratification. The accuracy of the score is improved with the addition of ultrasound.

Plan of care/prognosis
What is my chance of admission and will a CT change my chance of admission?
Patient Admission rates ranged from 4% to 19%, and limited evidence suggests admission rates are not affected by the use of CT.
What is the ED revisit rate and is it higher if a patient does not get a CT?
Both ED revisits ranged from 12% to 30% and limited evidence suggests this rate is not affected by imaging modality.
Clinician centered: what is the chance the patient will need a procedure (and therefore should have a CT)? Patient oriented: Will getting a CT change my chance of needing a procedure?

Both
The intervention rate varied from 6% to 33%, with the only population-level study having a 60-day intervention rate of 13% for patients initially discharged from the ED. Several studies suggested that imaging modality did not affect the procedure rate. Ultrasound results can risk stratify patients regarding the likelihood of needing a procedure.
Can ultrasound predict the likelihood of needing a procedure?

Both
Ultrasound can risk stratify patients: patients with moderate or greater hydronephrosis had an 18%-33% likelihood of having an intervention. Those with no or mild hydronephrosis had an intervention rate of 0%-10%.
Cost (time and money) What will I be charged for each option? Patient Patients in the United States will be charged between $2300 and $6000 for an ED visit for ureterolithiasis. These costs generally reflect the use of a CT scan.
How long will each option keep me in the ED?

Patient
Minimal evidence exists, but one study directly comparing imaging reported a shorter length of stay for patients receiving POCUS as compared to CT or radiology-performed ultrasound.

4.3.1
Summary of current evidence A total of 3 retrospective studies addressed the question of the prevalence of incidental findings (  40 These likely represent 64-slice scanners.

5.2
Stakeholder-derived question: How accurate is the low-dose CT scan?

5.2.1
Summary of current evidence A total of 4 systematic reviews and 1 meta-analysis report that the accuracy of the low-dose CT is comparable with the standard-dose CT in the diagnosis of ureterolithiasis ( Table 4 in Supplement B). 14,15,[41][42][43] Sensitivities ranged from 90% to 100%, and specificities ranged from 86% to 100%. The lowest levels of accuracy were found in the studies that included ultra-low-dose CT.

Summary of current evidence
A total of 8 studies, including 3 systematic reviews, addressed ultrasound accuracy ( Table 5 in Supplement B). 6,7,12,29,[44][45][46][47] These studies did not consistently use the same reference standard. The following 3 different aspects of ultrasound were evaluated: ability to detect hydronephrosis, association between hydronephrosis seen on ultrasound and ureterolithiasis, and overall ability to diagnose ureteral stone. In the detection of hydronephrosis, ultrasound was found to have a sensitivity range between 72% and 90.8% and a specificity range between 73% and 87% compared with CT. 29,44,47 The studies showed that hydronephrosis did strongly correlate with the presence of a stone. Hydronephrosis was found to have a positive predictive value between 77% and 92.9%, a negative predictive value between 65% and 88.5%, a sensitivity between 76% and 85.2%, and a specificity between 37% and 94.5%. 29,44,46,47 Regarding the overall ability of ultrasound to diagnose stones, the sensitivity ranged between 70.2% and 85%, and the specificity ranged from 50% to 75.4%. 7,12

5.4
Stakeholder-derived question: Can the presence of a stone be predicted by other factors without using CT?
Of note, several articles suggested that the elimination of race as part of the STONE score might improve its test characteristics in settings with a different racial makeup from the original study. 55,56

Stakeholder-derived question: What is my chance of admission and will a CT change my chance of admission?
6.1.1 Summary of evidence Admission rates ranged from 4% to 19% in the 7 studies included, with studies including patients who were older and sicker having higher admission rates ( Table 7 in Supplement B). 1,12,23,28,37,59,60 Ultrasound findings could risk stratify patients, with patients with hydronephrosis having a higher likelihood of an admission, but most patients with hydronephrosis were discharged. There are limited data comparing the admission rates for those receiving versus those not receiving a CT scan. The 1 study rated as "good" in this group found that the likelihood of admission was not affected by the receipt of a CT. 12

6.2.1
Summary of current evidence ED revisits at 30-60 days ranged from 12% to 30% in these 6 studies ( Table 8 in Supplement B). 12,28,44,58,60,61 Of these studies, 2 RCTs and 2 additional studies made direct comparisons that suggested a diagnostic pathway involving ultrasound (as the only imaging or first imaging) will not lead to an increase in ED revisits.

6.3
Clinicians: What is the overall likelihood the patient will need a procedure (and therefore should have a CT)? Patient-oriented question: Will getting a CT change my chance of needing a procedure? Stakeholder-derived question: Can ultrasound predict the likelihood of needing a procedure?

Summary of current evidence
In 9 studies, the urologic procedure rate varied from 6% (at 7 days) to 33% (at 30-60 days) (Table 9a and 9b in Supplement B). 22,23,24,59,[62][63][64][65][66][67][68][69][70] The only large population-level study showed a procedure rate of 13% in patients aged 18-64 years who were initially discharged from the ED. Stone size and location (as judged via CT), pain scores on discharge, and having private health insurance were found to be associated with a subsequent intervention in some studies. Studies that compared imaging modalities did not find differing rates or timing of urologic intervention based on initial imaging modality.
A total of 4 studies evaluated if ultrasound can predict the likelihood of a urologic procedure. The results suggested that ultrasound can risk stratify patients and give the approximate likelihood a patient will need an intervention. Patients with moderate or greater hydronephrosis or a stone visualized on ultrasound had an 18%-33% chance of needing an intervention, whereas those with no or mild hydronephrosis had a rate of intervention that ranged from zero to 10%.

7.1
Stakeholder-derived question: What will I be charged for each option?

Summary of current evidence
Only 5 studies addressed the issue of charges or costs for an ED visit for nephrolithiasis (Table 10 in Supplement B). [71][72][73][74][75] Current data suggest that patients in the US will be charged between $2300 and $6000 for an ED visit for ureterolithiasis. As population-level data demonstrated that the majority of these patients received a CT scan during their visit, and costs for POCUS and radiology-performed ultrasound are lower than the costs for CT, it is possible, but not clearly demonstrated, that an ED visit using only ultrasound would result in lower charges.
In one study that compared the mean costs (not charges) for patients who were randomly assigned to different initial imaging modalities, the costs of hospitalization vastly outweighed the ED costs even though most patients were discharged. As admission rates did not differ by initial imaging, the mean costs by group did not differ. However, looking solely at ED costs, 1 study found that these were trivially lower for those in the radiology-performed ultrasound group versus the CT-first group ($423 vs $449; P < 0.0001). 74  Lastly, we failed to see an effect of CT on many patient-centered outcomes, but lack of evidence of an effect is not equivalent to evidence of lack of an effect. In a few areas, high-quality evidence, such as multicenter RCTs, demonstrated no effect, but not all areas had a substantial evidence base from which to draw.

DISCUSSION
Our scoping review provides a broad understanding of the current evi- for discharge, appears to be low and should not be the driving reason for routine CT.
Despite the breadth of our review, only 2 RCTs were found that attempted to discern the effects of altering initial imaging modality. The first, from Smith-Bindman et al, compared an "ultrasoundfirst" diagnostic pathway to a "CT-first" pathway via 3 arms: POCUS first, radiology performed ultrasound first, and CT first. 12 This wellexecuted multicenter RCT reported decreased total radiation for the ultrasound-first arms with no increase in "high-risk" (or delayed) diagnoses. Subsequent secondary analyses did not find a difference in the admission or procedure rates and only a small difference in ED costs (with the arm receiving a radiology-performed ultrasound having lower mean costs than the CT-first arm). The second RCT, from Lindqvist et al, compared immediate CT to delayed CT for patients with suspected uncomplicated renal colic. The results of this study also did not support the idea that immediate CT is safer or changes other outcomes. 28 However, in both studies clinicians were able to order a CT when they felt it was necessary, regardless of the arm to which the patient was randomly assigned. These studies highlight that although routine CT is not necessary, routine avoidance of CT is likely not appropriate either.
It is notable that although we found many studies about diagnosing ureterolithiasis with ultrasound and risk stratifying patients with various risk stratification tools, we found no studies evaluating gestalt. It is unclear, from this literature, how physician gestalt may play a role.
However, if one considers that both RCTs allowed physicians to order CTs for the non-CT groups, that safety outcomes were the same, and that many patients did not receive a CT, this suggests that physicians' gestalt about who needed a CT was likely fairly accurate.
Lastly, our review did suggest that avoiding CT-and using SDM to decide about the use of immediate CT-may be more appropriate for younger patients, defined as younger than 50 or 55 years in different studies. This is because the main benefit of CT-finding a dangerous alternative diagnosis-is more likely as patients get older, whereas the main risk-of the radiation causing a future cancer-is higher for younger patients. Because of this, the decision aid created in conjunction with this scoping review is intended for use with patients aged 18-55 years. 8 Based on this scoping review, future studies should not focus solely on the diagnostic utility of imaging modalities, but should attempt to include the effects of imaging modality on prognosis, such as interventions, ED revisits, admissions, and other patient-oriented outcomes.

ACKNOWLEDGMENTS
Dr. Schoenfeld is supported by a K08 from the Agency for Healthcare Research and Quality (5K08HS025701-02). Dr. Westafer is supported by a K12 from the National Heart, Lung, Blood Institute (1K12HL138049-01).

AUTHOR CONTRIBUTIONS
ES and LW designed the study with help from BG. ES, ED, and SG carried out data abstraction and analysis. ES, ED, SG and LW discussed and collated the results, and all authors contributed to the drafting of the manuscript. ES takes responsibility for the work as a whole.