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Computed Tomography (CT) Prioritization

Last updated on August 31, 2023
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Effective Date: September 16, 2020

Scope

This guideline summarizes suggested wait times for common indications where Computed Tomography (CT) is the recommended first imaging test. The purpose is to inform primary care practitioners of how referrals are prioritized by Radiologists and Radiology departments across the province. This guideline is an adaptation of the British Columbia Radiological Society (BCRS) CT Prioritization Guidelines (2013).1 Management of the listed clinical problems is beyond the scope of thisguideline. However, in some cases, notes and alternative tests are provided for additional clinical context. Primary care practitioners are encouraged to consult a Radiologist if they have any concerns or questions regarding which appropriate imaging test to choose for a problem. If in doubt consult with a Radiologist and review provincial guidance materials.2

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Background

The 2013 BCRS CT Prioritization Guidelines were developed to provide imaging departments with a consistent, provincial approach to prioritizing commonly ordered CT tests according to suggested maximum wait times. The BCRS guidelines were developed by consensus and are based on BC expert opinion with representation of Radiologists from across the province.

Several considerations apply:

  • These are guidelines, and as such, are designed to apply in general terms. They are not intended to replace clinical judgement or practitioner-to-practitioner discussion.
  • Prioritization levels were selected to match other similar guidelines for Magnetic Resonance Imaging (MRI) and Ultrasound (US) and are typically assigned by Radiologists rather than referring practitioners.
  • These guidelines should not be applied rigidly to each case, as varying clinical factors may shift an indication from one priority level to another.
  • Access to CT and the ability to respond to CT requests will depend on resources and local availability.
  • Providing detailed patient information is essential to aid with the prioritization process.
  • The clinical topics included in this guideline represent broad examples, and do not encompass all possible scenarios or all requirements for CT examinations.

Priority Level Definitions

The priority levels defined below (Table 1) are in alignment with the Canadian Association of Radiologists national designation Five Point Classification System.3

Table 1: Priority Level Definitions

Priority Level Clinical Example Maximum Suggested Wait Time
P1 An examination immediately necessary to diagnose and/or treat life-threatening disease. Such an examination will need to be done either stat or not later than the day of the request. Immediately to 24 hours
P2 An examination indicated within one week of a request to resolve a clinical management imperative. Maximum 7 calendar days
P3 An examination indicated to investigate symptoms of potential importance. Maximum 30 calendar days
P4 An examination indicated for long-range management or for prevention. Maximum 60 calendar days
P5 Timed follow-up exam or specified procedure date recommended by Radiologist and/or clinician.  

Source: Adapted from the Canadian Association of Radiologists National Maximum Wait Time Access Targets for Medical Imaging.

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Prioritization of Potential Diagnoses

CT is widely indicated for and includes but is not limited to the following4 (see separate sections for specific clinical indications):

  • Cerebrovascular accidents
  • Imaging in trauma
  • Staging and monitoring of malignancies
  • Imaging of the chest and abdominal conditions
  • Providing pre-operative assessment of complex masses
  • Assessing post-operative complications
  • Imaging guided intervention: injections, fine needle aspiration, core biopsy and fluid drainage

The following potential diagnoses, where CT is the recommended first test, are grouped according to body system and then further subdivided into priority levels. For each system, an overview table is presented followed by a more detailed table outlining additional notes and alternative tests where CT may be less appropriate due to ionizing radiation exposure.

For CT also consider the patient risk of radiation exposure, refer to Appendix A: Radiation Exposure.

Referring practitioners should include clear, pertinent clinical history on radiology requisitions to assist the triaging/prioritizing of examinations and interpretation of images and may consider noting the priority directly on the requisition where possible.

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Head and Neck

Head and Neck: Overview

P1 P2 P3 P4 P5
Immediately to 24 hours Max 7 calendar days Max 30 calendar days Max 60 calendar days  
  • Acute trauma to head, facial bones, spine and orbit (e.g. foreign body)
  • Decreased or altered level of consciousness
  • Stroke / Transient Ischemic Attack (TIA)
  • Acute thunderclap headache: suspected acute subarachnoid hemorrhage
  • Intracranial venous thrombosis
  • Acute infection – neck or intracranial
  • Dissection - Carotid or Vertebral
  • Acute orbital mass or inflammation with imminent visual loss
  • Head and neck malignancy – preoperative, and/or staging
  • Post-operative neurosurgical patients
  • Orbital pathology including new visual symptoms, and/or acute proptosis
  • Evaluate rapid deterioration in patient with known malignant disease
  • Headaches (recently worsening or with neurological findings), red flags
  • Seizures, 1st documented
  • Vertebrobasilar insufficiency
  • Sellar pathology (if MRI not possible)
  • Hearing loss or tinnitus
  • Pulsatile tinnitus
  • Acute Psychosis – 1st episode
  • Screening for intracranial aneurysms – family history Computed Tomography Angiography (CTA)
  • Mild cognitive impairment / Dementia work-up
  • Sinus disease without intracranial complication
  • Temporomandibular Joint (TMJ) pathology
  • Cholesteatoma, chronic otitis media
  • Hematoma – reassessment of known chronic subdural
  • Postoperative followup (i.e. meningioma resection, pituitary adenoma)

Head and Neck: Notes and Alternative Tests

  Potential Diagnosis Notes and Alternative Tests
P1 Stroke / Transient Ischemic Attack (TIA)
  • CT head is usually combined with CTA and perfusion imaging when acute stroke is suspected
  • CTA (or carotid US) should be considered when TIA suspected, may not be performed on emergent basis
Acute thunderclap headache acute: suspected acute subarachnoid hemorrhage
  • CTA should be considered
P2 Postoperative neurosurgical patients
  • Typically ordered by a Neurosurgeon
Headaches (recently worsening or neurological findings), red flags
P3 Pulsatile tinnitus
  • CT is the preferred test
  • MRI suggested for sensorineural hearing loss
Acute Psychosis – 1st episode
  • Expedited as per specialist (i.e. psychiatry) request
P4 Postoperative follow-up (i.e. meningioma resection, pituitary adenoma Rx)
  • Date of imaging determined by the referring specialist

Appropriate Imaging for Common Situations in Primary and Emergency Care5

Headaches
Imaging is not recommended unless red flags are present

Consider imaging in the following red flag situations:

  • Sudden onset of severe headache (thunderclap)
  • Recurrent headache with unexplained focal neurological signs or other symptoms with focal deficits
  • New onset in the setting of HIV or cancer
  • Abnormal neurological exam
  • Suspected intracranial infection
  • New onset or worsening seizure
  • New headache aged >50
  • Headache causing awakening from sleep
  • Papilledema
  • Worsening headache frequency or severity in a patient with previous headache history or recent head trauma
  • Acute head trauma if indicated by CT head clinical decision rule

Think twice before requesting head CT for:

  • Migraine
  • Syncope
  • Temporal arteritis
  • Multiple sclerosis
  • Sinusitis
  • Chronic post-concussion syndrome with normal neurological exam

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Spine

Spine Overview

P1 P2 P3 P4 P5
Immediately to 24 hours Max 7 calendar days Max 30 calendar days Max 60 calendar days  
  • Acute spinal trauma
  • Acute myelopathy, (cord compression, cauda equina syndrome)
  • Discitis / osteomyelitis, suspected
  • Evaluation of rapidly deteriorating malignant disease
  • Sciatica with progressive neurological deficit
  • Back pain with red flags
  • Spinal stenosis with bowel or bladder dysfunction
  • Persistent neck or back pain of more than six weeks, after trial of conservative treatment, with or without objective neurological findings (radiculopathy)
  • Postoperative spine with chronic pain
  • Postoperative follow-up

Spine: Notes and Alternative Tests

  Potential Diagnosis Notes and Alternative Tests
P1 Acute myelopathy (cord compression, cauda equina syndrome)
  • MRI usually preferred for cervical spine assessment
Discitis / osteomyelitis, suspected
  • If MRI contraindicated or not available
P2 Back pain with red flags
P3 Persistent back pain of more than six weeks, with or without objective neurological findings (radiculopathy)

Appropriate Imaging for Common Situations in Primary and Emergency Care5

Back Pain
Imaging is not recommended unless red flags are present

Consider imaging in the following red flag situations:

  • Severe or progressive neurological deficit (e.g. cauda equina, saddle anesthesia)
  • Significant acute traumatic event immediately preceding onset of symptoms
  • Suspected compression fracture or pathological fracture (risk factors include long term steroid use)
  • Suspected cancer, cancer related complication, or history of cancer (e.g. night sweats or night pain)
  • Suspected infection (e.g. discitis/osteomyelitis, epidural abscess), risk factors include history of IV drug use, history of fever or chills
  • Suspected spinal epidural hematoma
  • Older age with first episode of back pain
  • Low back pain lasting greater than six months

Note: Back pain may be due to conditions other than spinal and may warrant imaging of the abdomen or pelvis.

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Musculoskeletal/Extremity

Musculoskeletal/Extremity: Overview

P1 P2 P3 P4 P5
Immediately to 24 hours Max 7 calendar days Max 30 calendar days Max 60 calendar days  
  • Acute fractures with inconclusive plain X-rays, or for preoperative evaluation by an Orthopedic surgeon
  • Necrotizing fasciitis
  • Acute vascular insufficiency to extremity
  • Fractures without neurovascular compromise, decision regarding surgery or for surgical planning
  • Assess postoperative complications, hardware or fracture alignment
  • Osteomyelitis (if MRI contraindicated)
  • Tumor – primary bone or soft tissue
  • Tumor musculoskeletal –
    biopsy planning
  • Unstable metastatic bone lesion
  • Orthopedic preoperative planning (not P2)
  • Assess progress of fracture healing
  • Characterization of arthritis, gout
  • Assessment of painful prosthesis
  • Monitoring of multiple myeloma, bone metastases where radiographs are inadequate
  • Evaluation of chronic vascular insufficiency
  • Postoperative follow-up

Musculoskeletal/Extremity: Notes and Alternative Tests

  Potential Diagnosis Notes and Alternative Tests
P1 Acute vascular insufficiency to extremity
  • CTA
P2 Tumor musculoskeletal - biopsy
  • Only after evaluation with MRI and orthopedic oncology consultation
P3 Assess progress of fracture healing
  • CT indicated If plain film is inconclusive
P4 Characterization of arthritis, gout
  • Dual energy CT can be used for the characterization of crystalline arthropathies (if available)
Evaluation of chronic vascular insufficiency
  • CTA

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Chest

Chest: Overview

P1 P2 P3 P4 P5
Immediately to 24 hours Max 7 calendar days Max 30 calendar days Max 60 calendar days  
  • Major trauma
  • Acute aortic dissection
  • Acute pulmonary embolism (in pregnancy, see notes)
  • Esophageal rupture or tear
  • Mediastinitis
  • Massive hemoptysis
  • Rapidly progressive shortness of breath (without a known underlying etiology)
  • Hemoptysis, increasing in frequency and volume
  • Acute interstitial lung disease
  • Further characterization of mediastinal, lung or pleural mass
  • Lymphadenopathy (hilar, mediastinal)
  • Evaluating atypical lung or pleural infection and symptomatic patients with a cough
  • High clinical suspicion for pneumonia/infection with a normal chest radiograph
  • Clinical deterioration if post lung transplant or immunocompromised
  • Non-resolving pneumonia on chest X-ray
  • Chronic interstitial lung disease – acute exacerbation
  • Chronic Interstitial lung disease – evaluation of progression
  • Bronchiectasis
  • Characterization of small pulmonary nodule
  • Evaluation for lung cancer in high risk individuals*
  • Postoperative follow-up
  • Follow-up of small pulmonary nodule
  • Stable aneurysm / dissection follow-up

Chest: Notes and Alternative Tests

  Potential Diagnosis Notes and Alternative Tests
P1 Acute pulmonary embolism (in pregnancy, see notes)
  • Local imaging consultation is recommended
P2 Acute interstitial lung disease
  • New diagnosis or deterioration of existing disease
  • Acute exacerbation, deteriorating or clinical change
Evaluating atypical lung or pleural infection and symptomatic patients with a cough
  • Chest x-ray may be normal, typically CT required if not responding to regular treatment
High clinical suspicion for pneumonia/infection with a normal chest radiograph
  • Atypical infection (e.g. fungal)
Clinical deterioration if lung Transplant or immunocompromised
  • Complication, deterioration, change in respiratory status
P4 Evaluation for lung cancer in high risk individuals
P5 Follow-up of small pulmonary nodule
Stable aneurysm/dissection follow-up
  • Without chest X-ray or symptomatic changes
  • Usually requested by specialists

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Cardiac

Cardiac: Overview

P1 P2 P3 P4 P5
Immediately to 24 hours Max 7 calendar days Max 30 calendar days Max 60 calendar days  
  • Acute/ unstable infective endocarditis
  • Suspected prosthetic valve dehiscence
  • Chest pain (typical / atypical in high risk patient) (Coronary CTA)
  • Stable suspected infective endocarditis
  • Myo-/pericarditis (MRI contraindicated)
  • Ventricular assist device evaluation
  • Atypical chest pain in low risk patient (Coronary CTA)
  • CT myocardial perfusion for ischemia (MRI contraindicated)
  • Atrial fibrillation preablation work-up
  • Valve replacement workup (TAVR / TMVR)
  • Coronary artery calcium score
  • Follow-up pericardial effusion
  • Chest pain after coronary artery bypass graft (CABG)
  • Postoperative follow-up

Cardiac: Notes and Alternative Tests

  Potential Diagnosis Notes and Alternative Tests
P1 Acute/ unstable infective endocarditis
  • Echocardiography would be the best first test
P2 Chest pain (typical / atypical in high risk patient)
  • Coronary CTA
Stable suspected infective endocarditis
  • Echocardiography would be the best first test
Myo-/pericarditis (if MRI is contraindicated)
  • Echocardiography would be the best first test
Ventricular assist device evaluation
  • LVAD/RVAD/BiVAD
P3 Atypical chest pain in low risk patient (CCTA)
  • Coronary CTA
CT myocardial perfusion for ischemia (MRI contraindicated)
  • Usually ordered by specialists; performed at specialist sites
Valve replacement workup (TAVR / TMVR)
  • Usually ordered by specialists; performed at specialist sites

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Abdomen and Pelvis

Abdomen and Pelvis: Overview

P1 P2 P3 P4 P5
Immediately to 24 hours Max 7 calendar days Max 30 calendar days Max 60 calendar days  
  • Abdominal trauma
  • Abdominal aortic aneurysm rupture
  • Appendicitis
  • Diverticulitis
  • Bowel obstruction
  • Suspected bowel perforation
  • Bowel ischemia
  • Acute GI bleeding
  • Renal colic
  • Cholecystitis or biliary obstruction
  • Solid organ abscess/infection or collection
  • Pelvic inflammatory disease
  • Post-operative complications
  • Suspected hernia, with acute symptoms
  • Metastasis preoperative workup
  • Tumor – search for primary in the abdomen/pelvis
  • Pancreatitis complications
  • Malignant disease; staging prior to treatment or evaluation if concern regarding progression
  • Solid organ masses (intraabdominal, pelvic for further characterization)
  • Workup of asymptomatic abdominal mass
  • Renal or liver transplant complications
  • Renal mass to determine whether a cyst or tumor
  • Adrenal mass, work-up of incidental finding
  • Pre-operative evaluation of aneurysms
  • Suspected tumor recurrence
  • Unexplained bloating, anemia, chronic abdominal pain or weight loss
  • Inflammatory bowel disease
  • Chronic mesenteric ischemia
  • Colonic polyps
  • Hernia without acute symptoms
  • Renal stone burden
  • Renal artery stenosis
  • Follow-up of treated malignancy
  • Follow-up for aneurysm growth
  • Postoperative follow-up

Abdomen and Pelvis: Notes and Alternative Tests

  Potential Diagnosis Notes and Alternative Tests
P1 Abdominal trauma
  • Blunt or penetrating trauma
Abdominal aortic aneurysm rupture
  • Performed with a CTA protocol
Appendicitis
  • US is preferred first imaging examination particularly in pediatric, pregnant or young female patients
Suspected bowel perforation
  • Water-soluble oral contrast may assist in locating site of possible perforation
Cholecystitis or biliary obstruction
  • Can be considered if US inconclusive
Pelvic inflammatory disease
  • Ultrasound is usually the first test
P2 Solid organ masses (intra-abdominal or pelvic for characterization)
  • MRI is a helpful adjunct particularly for pelvic masses
Renal or liver transplant complications
  • US usually the initial test
  • CT for inconclusive results
P3 Adrenal mass, work-up of incidental finding
  • MRI can be considered if CT inconclusive
  • Correlation with endocrinology profile recommended
P4 Colonic polyps
  • CT Colonography is indicated for patients who have had a positive FIT, an incomplete colonoscopy, who have contraindications for colonoscopy or preference for CTC
Hernia without acute symptoms
  • US is first-line test for acute painless hernia/chronic hernia
Renal stone burden
  • First line test is usually US, which may be supplemented with CT KUB (kidney, urinary, bladder) or KUB radiograph as needed
Renal artery stenosis
  • Performed as a CTA
P5

Follow-up of treated malignancy
  • Usually booked as P5 as determined by the referring practitioner

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Pediatric

Consider alternatives to CT, if appropriate, to reduce radiation exposure for pediatric patients. See Appendix A: Radiation Exposure, for more information.

Pediatric: Overview

P1 P2 P3 P4 P5
Immediately to 24 hours Max 7 calendar days Max 30 calendar days Max 60 calendar days  
  • Major trauma
  • Non-accidental trauma suspected, with neurological syndrome
  • Stroke
  • Anterior Mediastinal Mass
  • Chest / Abdominal Mass evaluation and staging
  • Infection – immunecompromised patient
  • Congenital Heart Disease (see notes)
  • Complex intra-articular fracture
  • Headache with red flags
  • Orthopedic reconstruction preoperative imaging
  • Craniosynostosis
  • Congenital Lung Anomaly (see notes)
  • Postoperative follow-up

Pediatric: Notes and Alternative Tests

  Potential Diagnosis Notes and Alternative Tests
P1 Non-accidental trauma suspected, with acute neurological syndrome
  • P1 if acute neurological syndrome
  • Otherwise P2 with MRI as alternative
Stroke
  • Requires CT/CTA +/- perfusion imaging
Anterior Mediastinal Mass
  • Requires clinical evaluation for airway compression
P2 Chest, Abdominal mass evaluation and staging
  • MRI, PET-CT or MIBG SPECT-CT may be preferred depending on suspected tumor type. Referral to pediatric subspecialist prior to staging of suspected malignancy is recommended
Congenital Heart Disease
  • P2-P4 depending on indication; should be referred to Pediatric Cardiology for evaluation; imaging is performed at BC Children’s Hospital
P3 Headache with red flags
P4 Craniosynostosis
  • Best ordered in consultation with a Pediatrician or Neurosurgeon prior to imaging
Congenital Lung Anomaly
  • Usually ordered by specialists; performed at specialist sites

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Resources

Appendices

References

  1. BC Radiological Society. CT Prioritization Guideline (2013)
  2. Medical Imaging Advisory Committee. Provincial Guidance for Medical Imaging Services within British Columbia During the Pandemic Phases (June 2020).
    http://www.bccdc.ca/Health-Professionals-Site/Documents/COVID19_MedicalImagingGuidePractitioners.pdf
  3. Canadian Association of Radiologists National Maximum Wait Time Access Targets for Medical Imaging (MRI and CT).
    https://car.ca/wp-content/uploads/car-national-maximum-waittime-targets-mri-and-ct.pdf
  4. International Radiology Quality Network. Referral Guidelines for Diagnostic Imaging: A Supporting Tool for Healthcare Professionals in the Selection of Appropriate Procedures. 2017.
    http://www.isradiology.org/quality-guidelines
  5. BC Guidelines. Appropriate Imaging for Common Situations in Primary and Emergency Care
    https://www2.gov.bc.ca/gov/content/health/practitioner-professional-resources/bc-guidelines/appropriate-imaging

This guideline is based on expert BC clinical practice current as of the effective date. This guideline was developed by the Guidelines and Protocols Advisory Committee based on the British Columbia Radiological Society Computed Tomography Prioritization Guidelines (2013), and approved by the Medical Services Commission.

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THE GUIDELINES AND PROTOCOLS ADVISORY COMMITTEE

The principles of the Guidelines and Protocols Advisory Committee are to:

  • encourage appropriate responses to common medical situations
  • recommend actions that are sufficient and efficient, neither excessive nor deficient
  • permit exceptions when justified by clinical circumstances

Contact Information:

Guidelines and Protocols Advisory Committee

PO Box 9642 STN PROV GOVT

Victoria BC V8W 9P1

Email: hlth.guidelines@gov.bc.ca

Website: www.BCguidelines.ca

Disclaimer

The Clinical Practice Guidelines (the guidelines) have been developed by the BC Cancer Primary Care Program, Family Practice Oncology Network and the Guidelines and Protocols Advisory Committee, on behalf of the Medical Services Commission. The guidelines are intended to give an understanding of a clinical problem, and outline one or more preferred approaches to the investigation and management of the problem. The guidelines are not intended as a substitute for the advice or professional judgment of a health care professional, nor are they intended to be the only approach to the management of clinical problem. We cannot respond to patients or patient advocates requesting advice on issues related to medical conditions. If you need medical advice, please contact a health care professional.

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