Defensive medicine and advanced imaging overuse in emergency departments: A focused review of imaging stewardship and overcrowding

Table 1 Clinical scenarios prone to advanced imaging overuse in the emergency department, the decision rules or stewardship strategies that address them, the populations in which those rules apply, and the recommended first-line imaging approach

Clinical scenario	Population	Principal driver of overuse	Decision rule or stewardship strategy	Eligibility and limitations	Recommended first-line imaging approach	Ref.
Minor head trauma	Adult	Fear of missed intracranial hemorrhage	Canadian CT Head Rule; NEXUS Head CT instrument	Canadian CT Head Rule: Blunt injury with witnessed loss of consciousness, amnesia or disorientation and Glasgow Coma Scale 13-15. Not derived or validated in children	Apply the rule first; non-contrast head CT in rule-positive patients. In validated low-risk patients the rule supports omitting CT	[61,62,64]
Syncope, dizziness or vertigo without focal neurological deficit	Adult	Concern for stroke or intracranial mass despite low yield	American College of Emergency Physicians clinical policy on syncope[63]; Head-Impulse, Nystagmus, Test-of-Skew examination in acute vestibular syndrome[66]	Head-Impulse, Nystagmus, Test-of-Skew applies only to an acute vestibular syndrome, that is, vertigo with nystagmus, nausea or vomiting, head-motion intolerance and unsteady gait, and requires a trained examiner. It is not a screening test for undifferentiated dizziness	Routine cranial CT or magnetic resonance imaging has low yield in patients without focal deficit in the populations studied; risk-stratify before imaging	[31,59,63,66]
Suspected pulmonary embolism	Adult	Nonspecific dyspnea or chest pain; fatal if missed	Wells score; Pulmonary Embolism Rule-out Criteria; age-adjusted D-dimer	Pulmonary Embolism Rule-out Criteria apply only when the clinician has already judged clinical probability to be low; not for moderate or high pre-test probability. Age-adjusted D-dimer, with a cutoff of age multiplied by 10 µg/L, was validated in patients aged 50 years or older with a non-high clinical probability[115]	Risk-stratify first; CT pulmonary angiography in patients with a high clinical probability or a positive D-dimer result, and avoid it in low-risk patients who are negative by the Pulmonary Embolism Rule-out Criteria	[27,28,68,69,115]
Renal colic, recurrent or known stone disease	Adult	Low threshold for CT given high accuracy	Ultrasonography-first pathway; low-dose CT when CT is required	Evidence is from a randomized trial in emergency patients with suspected nephrolithiasis; applies to a typical recurrent presentation. Initial ultrasonography does not exclude the need for subsequent CT	Ultrasonography first; reserve low-dose non-contrast CT for diagnostic uncertainty or suspected complication	[5,70]
Nonspecific, non-traumatic low back pain	Adult	Patient expectation; reassurance imaging	Red-flag criteria; Choosing Wisely	The recommendation applies to non-traumatic low back pain in the absence of red flags or pathologic indicators; the presence of any red flag, such as neurological deficit, history of malignancy or suspected infection, removes the patient from this recommendation	No emergency lumbar imaging in the absence of red flags	[71,72]
Cervical spine trauma	Adult	Reluctance to miss unstable cervical spine injury	NEXUS C-Spine criteria; Canadian C-Spine Rule	Canadian C-Spine Rule applies to alert, stable trauma patients with a Glasgow Coma Scale score of 15 and normal vital signs, and excludes age under 16 years, penetrating trauma, acute paralysis and known vertebral disease. NEXUS requires a reliable examination, which distracting injury or intoxication may preclude	Clinically clear low-risk patients with the rule; cervical CT in rule-positive patients	[47,65,75]
Minor head trauma	Pediatric	Parental anxiety; limited history from a distressed or preverbal child	Pediatric Emergency Care Applied Research Network head injury rule; as low as reasonably achievable principle and Image Gently	Derived and validated in children under 18 years with a Glasgow Coma Scale of 14-15 presenting within 24 hours of blunt head trauma; separate algorithms apply above and below 2 years of age	Observation rather than CT in the very-low-risk group; a systematic review of implementation studies reported a median 27% relative reduction in head CT (relative risk 0.73, interquartile range 0.60 to 0.89), with safety outcomes inconsistently reported across studies	[45,81,82]
Abdominal pain or suspected appendicitis	Pediatric	Radiation risk; diagnostic uncertainty	Ultrasonography-first; rapid magnetic resonance imaging where available	Ultrasonography is operator-dependent and non-visualization of the appendix is common; a non-diagnostic study does not exclude appendicitis. Rapid magnetic resonance imaging availability is limited outside specialist centers	Ultrasonography first; if it is non-diagnostic and suspicion persists, rapid magnetic resonance imaging or contrast-enhanced CT	[5,76,83,113]

NEXUS: National Emergency X-Radiography Utilization Study; CT: Computed tomography.

Table 2 Emergency department imaging stewardship interventions graded by the strength of the supporting evidence, with the stakeholders involved, the point of workflow integration, suggested monitoring metrics, and potential unintended consequences

Intervention	Strength of evidence in emergency populations	Principal stakeholders	Workflow integration point	Suggested monitoring metrics	Potential unintended consequences	Ref.
Validated clinical decision rules	Strongest. Multiple prospective derivation and validation cohorts with defined eligibility criteria; implementation effect varies by site	Emergency physicians; nursing triage; radiology	At clinical assessment, before the order is placed	Rule documentation rate; rule-concordant imaging; missed clinically important injury; unscheduled return within 72 hours	Application outside the validated population; rule fatigue; documentation performed after the imaging decision	[61,62,65,68,69,75,82]
Computerized clinical decision support at order entry	Moderate to strong. Observational and implementation studies report improved appropriateness; effect depends on the guideline library and local configuration	Emergency physicians; radiology; informatics	Embedded in computerized order entry	Appropriateness score distribution; alert override rate; duplicate examinations avoided; time from order to acquisition	Alert fatigue; workflow interruption; systematic overriding; gaming of indication fields	[99,102,105]
Audit and feedback	Moderate but variable. Effects across sites are inconsistent and depend on timeliness and credibility of the data	Department leadership; quality improvement teams; individual clinicians	Periodic, outside the clinical encounter	Individual and peer ordering rates; diagnostic yield; guideline adherence; case mix adjustment	Perceived as punitive; distrust of unadjusted data; attention shifts to the measured test only	[22,48,58]
Choosing Wisely and awareness campaigns	Limited when used alone; greater when embedded in pathways and order sets	Professional societies; department leadership; patients	Local pathway and patient communication material	Uptake of targeted recommendations; rate of the specific low-value examinations named	Little effect without structural reinforcement; symbolic adoption without workflow change	[58,72,97,98]
Shared decision-making and decision aids	Limited and indirect in the emergency setting; most evidence is from non-emergency contexts or small studies	Emergency physicians; patients and families	During the clinical consultation	Documented discussion; patient-reported understanding and satisfaction; imaging rate in eligible presentations	Time cost in a crowded department; unequal uptake across language and health-literacy groups	[9,24,51]
Artificial intelligence-assisted appropriateness and triage tools	Emerging. Evidence of effect on imaging appropriateness is limited; where external validation has been performed, most algorithms lose performance on the external dataset	Radiology; informatics; emergency physicians; governance committee	Order entry, record extraction, or radiology worklist, depending on the tool	Local validation performance; drift monitoring; override rate; effect on report turnaround; equity of performance across subgroups	Automation bias; performance loss under dataset shift; opacity of the recommendation; unclear liability	[101,103,104,106,108,109]
Medico-legal reform and legal protection for guideline-concordant care	Weakest. Evaluated in few jurisdictions; the principal natural experiment found no accompanying reduction in advanced imaging	Legislators; hospital risk management; professional bodies	Outside the clinical pathway; institutional and legislative	Imaging rates before and after reform; malpractice claim frequency; clinician-reported medico-legal concern	Reform alone may not change behavior if institutional and consultant expectations are unchanged	[49,53,54]