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.