GC013 Emergency Radiology
Emergency radiology is the subspecialty of radiology focused on the rapid interpretation of imaging studies to diagnose acute, life-threatening conditions such as trauma, stroke, and vascular emergencies in urgent clinical settings.
Emergency Radiology – Comprehensive Exam-Ready Notes
Big Idea: Emergency radiology is about choosing the right imaging modality at the right time to answer a specific clinical question, without delaying life-saving management. The lecture systematically walks through common emergency presentations — head trauma, CNS infection, cord compression, pulmonary embolism, acute abdomen, blunt abdominal trauma, appendicitis, ruptured AAA, and acute scrotal pain — and for each asks: What is the imaging modality of choice?
Learning Objectives (from the lecture):
Approach to various common medical/surgical emergencies where imaging can aid diagnosis. Selection of the appropriate imaging modality. Importance of prompt diagnosis. [1]
How this fits into exams: Past papers repeatedly test "best imaging modality" for acute scenarios (MCQs 2020 Q1, 2022 Q1-2, 2025 Q61, Q72; SAQs 2016 Q9, 2017 Q6, 2021 Q8, 2022 Q1). The lecture gives you a framework to answer every single one of these.
1. General Principles of Emergency Radiology
The radiologist is a member of the management team. Examinations are tailored to the clinical situation. Accurate interpretation is required. All abnormalities must be communicated to the clinician — both verbally and written in case-notes. [1]
Why this matters: In an emergency, radiology is not just "request a scan and wait." The radiologist actively participates in clinical decision-making, tailors protocols (e.g., adding contrast phases, choosing the right modality), and has a duty to verbally communicate critical findings. Exam questions may test when to communicate with the radiologist and how to request urgent imaging.
Direct communication with Radiologist on-call. Please know your patient. Check INR, PT/PTT, blood counts for interventional radiology. Check period of fasting. Obtain informed consent. [1]
| Pre-Imaging Checklist | Why It Matters |
|---|---|
| Know your patient | You must provide a focused clinical question so the radiologist can tailor the study |
| Check coagulation (INR, PT/PTT, platelets) | Interventional procedures carry bleeding risk; abnormal coagulation = contraindication or need for correction |
| Fasting status | Oral contrast studies, sedation/anaesthesia require fasting; aspiration risk |
| Informed consent | Legal requirement, especially for contrast-enhanced or interventional procedures |
| eGFR | IV iodinated contrast is generally avoided if eGFR < 30 mL/min (use alternatives like V/Q scan, US) [2] |
Availability and rapid response to the radiology team is important…but there are limitations! Balance the potential delay caused by imaging and the need for urgent management. [1]
Translation: Don't let imaging delay life-saving treatment. A classic example: if a patient has clinical signs of tension pneumothorax, you perform needle decompression FIRST — you do NOT send them to radiology for a CXR [10]. Similarly, if testicular torsion is clinically likely, the patient goes to theatre; you don't wait for an ultrasound.
Ensure patient is haemodynamically stable, Check ABCs → Radiology [1]
This is the foundational algorithm: Clinical history and physical examination FIRST, then radiology. Imaging is an adjunct to clinical assessment, not a replacement.
2. Head Trauma
High Yield: Head Trauma Imaging
In most cases, non-contrast CT alone is sufficiently diagnostic to end the imaging workup. [1]
This is almost certainly the answer to any MCQ asking "best imaging modality for acute head injury." Non-contrast CT (NECT) is fast, widely available, and detects both haemorrhage (hyperdense on CT) and skull fractures.
Why non-contrast CT and not MRI?
- CT is fast (seconds), MRI is slow (30–60 minutes)
- CT is excellent at detecting acute blood (fresh blood is hyperdense due to haemoglobin)
- CT detects skull fractures on bone window
- MRI is contraindicated in unstable patients (requires the patient to lie still in a tube, magnets interfere with monitoring equipment)
- CT is available 24/7 in most emergency departments
Focal neurologic findings. Altered level of consciousness after trauma. Clinical signs of basilar fracture e.g. 'raccoon' eyes. Evidence of CSF leak from nose or ear. Penetrating head injury. Significant facial fracture. [1]
Expanded with Canadian CT Head Rules [3]:
| High Risk (for neurosurgical intervention) | Medium Risk (for brain injury on CT) |
|---|---|
| GCS < 15 at 2h post-injury | Retrograde amnesia > 30 min |
| Suspected open or depressed skull fracture | Dangerous mechanism (pedestrian struck, ejected from vehicle, fall > 1m or 5 stairs) |
| Signs of basal skull fracture (raccoon eyes, Battle sign, CSF otorrhoea/rhinorrhoea, haemotympanum) | |
| ≥ 2 episodes of vomiting | |
| Age ≥ 65 years |
SXR — generally not useful, except in suspected open and depressed fractures. [1]
Why is SXR useless? A normal skull X-ray does NOT exclude intracranial pathology (you can have a massive subdural haematoma with no skull fracture). A skull fracture on XR doesn't tell you about the brain. So SXR adds almost no useful clinical information in the CT era. The only exception is if you need to check for metallic foreign bodies before MRI, or in specific medicolegal settings. [3]
Clinical condition of the patient determines whether imaging is required or not. Glasgow Coma Scale gives indication of urgency of the examination. [1]
The lower the GCS, the more urgent the CT. A patient with GCS 3 needs immediate CT (or may need to go straight to theatre if there is an expanding pupil suggesting herniation).
| Pathology | CT Appearance | Key Features |
|---|---|---|
| Epidural haematoma (EDH) | Biconvex (lenticular) hyperdensity | Limited by suture lines; usually arterial (middle meningeal artery); 75% associated with skull fracture; classic "lucid interval" [4] |
| Subdural haematoma (SDH) | Crescent-shaped hyperdensity (acute) or isodensity (subacute) or hypodensity (chronic) | Crosses suture lines; venous (bridging veins); common in elderly/anticoagulated |
| Bilateral isodense subdural haematomas | Can be easily missed because isodense to brain | Look for effaced sulci, compressed ventricles, midline shift [1] |
| Subdural haematoma with mass effect and transtentorial herniation | Midline shift, effacement of basal cisterns | Neurosurgical emergency [1] |
| Cerebral contusion | Focal hyperdensity (haemorrhagic) or mixed density within brain parenchyma | Coup (at site of impact) and contrecoup (opposite side); common at frontal and temporal poles |
| Subarachnoid haemorrhage | Hyperdensity in sulci and cisterns | Traumatic SAH common; also consider aneurysmal SAH |
| Orbital wall fracture | Bony defect on bone window; orbital emphysema (air in orbit) | Medial wall (lamina papyracea) most commonly fractured [1] |
| Facial bone fractures | Best seen on CT coronal reformation | Le Fort classification; zygomatic arch, orbital floor, nasal bone [1] |
3D CT reconstruction / Bone window [1]
CT bone window and 3D reconstruction are used to delineate fracture lines and displaced fragments, which is particularly useful for:
- Surgical planning for depressed skull fractures
- Complex facial fractures
- Cervical spine fractures
MRI: Not 1st line imaging. Post-traumatic syndromes. Shear injury. Subtle haemorrhage/edema. MRA (Angiography). [1]
When to use MRI after head trauma:
- Diffuse axonal injury (DAI): CT may be normal but MRI shows multiple small foci of restricted diffusion/haemorrhage at grey-white matter junctions, corpus callosum, and brainstem [4]
- Post-concussion syndrome: When symptoms persist but CT is normal
- Brainstem injury: CT has poor resolution in posterior fossa
- Vascular injury: MRA can evaluate carotid/vertebral artery dissection
Exam Trap
Do NOT choose MRI as the first-line investigation for acute head trauma. CT is the answer. MRI is used later as a "problem-solving tool" for specific indications.
3. CNS Infection (Fever + Neurologic Signs)
Altered mental state and fever. Acute, severe headache. 1st seizure in an individual with fever and other constitutional signs. Immunocompromised host with new onset of neurological signs. [1]
Lumbar puncture is gold standard for diagnosis of meningitis. Cross-sectional imaging to exclude intra-cranial mass before LP and to identify parenchymal brain infection or extra-axial collection/empyema. MRI or CT (both with IV contrast). [1]
Why image before LP? If there is a space-occupying lesion (abscess, tumour) causing raised ICP, performing an LP can cause downward herniation (coning) and death. Imaging before LP excludes this. Signs that mandate imaging before LP include: focal neurological deficits, papilloedema, altered consciousness, seizures, and immunocompromised state.
Why IV contrast? Both brain abscess and empyema show ring enhancement on post-contrast imaging. Without contrast, you may miss the lesion or underestimate its extent.
| Pathology | CT Appearance | MRI Advantage |
|---|---|---|
| Multifocal brain abscesses (bacterial) | Ring-enhancing lesions on post-contrast CT [1] | Better delineation; DWI shows restricted diffusion (bright) — distinguishes abscess from tumour |
| TB abscess | Ring-enhancing lesion, often basal meningeal enhancement | MRI (T1 post-contrast) superior for posterior fossa and basal meningitis [1] |
| Empyema | Extra-axial enhancing collection | MRI better at differentiating from chronic SDH |
| Meningitis | CT may be normal; meningeal enhancement with contrast | MRI more sensitive for meningeal enhancement |
| Encephalitis (e.g., HSV) | Temporal lobe hypodensity/swelling | MRI shows early changes; characteristic temporal lobe involvement |
High Yield: Imaging Before LP
Cross-sectional imaging to exclude intracranial mass before LP — this is a cardinal rule in emergency medicine and neurology. Always image before LP if there are signs of raised ICP or focal neurology. [1]
4. Suspected Cord Compression (Acute Myelopathy)
Emergency diagnosis and treatment to prevent permanent neurologic dysfunction. Cord compression from spinal metastases or traumatic insults or acute disc prolapse. [1]
Once the cord is compressed beyond a critical duration, the damage is irreversible. The classic teaching is that neurological deficit present for > 48 hours is unlikely to fully recover. Hence, urgent imaging and management are required.
MRI — modality of choice for imaging spinal cord. [1]
Why MRI?
- MRI is the ONLY modality that directly visualizes the spinal cord parenchyma (CT shows bone well but cannot differentiate cord from CSF in detail)
- MRI shows cord oedema, compression, myelomalacia, and intrinsic cord lesions
- MRI shows epidural masses, disc protrusions, and vertebral body collapse with cord impingement
Clinical pearl for exams: When a patient with known cancer develops new back pain + lower limb weakness → suspect metastatic cord compression → MRI whole spine urgently + high-dose IV dexamethasone immediately (even before imaging) [10]
Blunt cervical spine trauma: Cervical spine radiographs → Suspected spinal cord injury → MRI; Suspected bone injury → CT [1]
| Modality | Role | Key Points |
|---|---|---|
| Plain X-rays (AP, lateral, open-mouth) | Basic views. All 7 cervical vertebrae must be visualised, including the cervicothoracic junction and craniocervical junction [1] | If C7/T1 is not seen (swimmer's view may help but CT is usually done) |
| Helical CT with multiplanar reformations | Spinal compromise from fracture, subluxation or dislocation. Further evaluation of equivocal plain film findings. Evaluation of areas not well visualised on standard views (C7/T1 or C1/2) [1] | Gold standard for bony injury; 3D reconstructions for surgical planning |
| MRI | To evaluate cord damage [1] | Assess cord oedema, ligamentous injury, disc herniation, epidural haematoma |
Practical flow in modern practice: In high-energy trauma, CT C-spine is often done upfront (as part of whole-body CT) rather than plain X-rays. Plain films are still the "textbook" first step and what the lecture teaches.
5. Acute Shortness of Breath — Pulmonary Embolism
Dyspnoea of sudden onset. Haemoptysis. Pleuritic chest pain. [1]
PE should be in the differential for any patient with sudden-onset breathlessness, especially with risk factors: recent surgery/immobilisation, malignancy, OCP use, previous VTE, long-haul travel.
Wide differential diagnosis: Pulmonary infection. Pulmonary oedema. Neoplastic disease e.g. massive pleural effusion, collapse. Others. [1]
CXR → CT pulmonary angiography (CTA/CTPA) → V/Q scan → Conventional pulmonary angiography (gold standard, but seldom necessary — invasive procedure!!) [1]
| Modality | Role | Key Points |
|---|---|---|
| CXR | First-line; often normal in PE but excludes other causes of SOB (pneumonia, pneumothorax, pleural effusion) | Hampton's hump, Westermark sign, enlarged pulmonary artery — all are insensitive |
| CTPA | Primary modality for diagnosing PE | Shows filling defects in pulmonary arteries; fast, widely available |
| V/Q scan | Alternative when CTPA cannot be done (contrast allergy, renal impairment, pregnancy) | Interpretation: high/intermediate/low probability |
| Conventional pulmonary angiography | Gold standard but seldom necessary | Invasive; reserved for equivocal cases or when intervention (embolectomy, thrombolysis) is planned |
| DVT lower limb Doppler US | If patient cannot have CTPA (e.g., pregnant, low eGFR) — finding a DVT in the right clinical context supports PE diagnosis [2] | Sensitivity 95% (excluding calf), specificity 98% [1] |
How to interpret these numbers:
- CTPA has good sensitivity AND specificity — it's the go-to test
- V/Q scan — if you include ALL probability categories (high + intermediate + low), it is very sensitive (98%) but terribly non-specific (10%). This means almost everyone will have "something" on V/Q, but most won't actually have PE. This is useless for ruling IN the diagnosis.
- V/Q scan (high probability only) — very specific (97%) but poor sensitivity (41%). A high-probability V/Q essentially confirms PE, but a normal or low-probability V/Q doesn't rule it out.
- Bottom line: CTPA is preferred; V/Q is reserved for patients who cannot receive IV contrast (eGFR < 30, contrast allergy) [2]
Limitations: lack of visualisation of subsegmental pulmonary arteries. Emboli isolated to subsegmental or smaller pulmonary arterial branches are the only manifestation of PE in 6%–30% of cases. [1]
This means CTPA can miss small peripheral emboli. The clinical significance of isolated subsegmental PE is debated — some argue it doesn't require anticoagulation in low-risk patients.
Ultrasound with colour Doppler and compression is the primary imaging modality for suspected DVT. Sensitivity (excluding calf) = 95%, specificity = 98%. [1]
Compression ultrasound is the technique: you compress the vein with the probe. If the vein compresses fully, there's no thrombus. If it doesn't compress, there is a DVT. "Excluding calf" means it's less reliable for isolated calf DVTs (which are smaller and harder to visualize).
6.1 Imaging Modality of Choice
Erect CXR to detect subphrenic gas. Left lateral decubitus AXR to detect free air in ill patients who cannot sit/stand. Erect AXR is NOT indicated. [1]
High Yield: Erect CXR, NOT Erect AXR
Erect AXR is not indicated for detecting pneumoperitoneum. The erect CXR is the correct first-line investigation because:
- Free air rises to the highest point — under the diaphragm
- CXR shows the diaphragm clearly; AXR does not show the diaphragm well
- Erect AXR was historically done but adds no value over erect CXR and delivers additional radiation
Why erect CXR? Free intraperitoneal air rises and collects under the diaphragm. On an erect CXR, you see a crescent of lucency (black) between the diaphragm and the liver/spleen. This is called subdiaphragmatic free air and indicates bowel perforation until proven otherwise.
Left lateral decubitus AXR: For patients who are too unwell to sit up or stand, you lay them on their LEFT side. Free air rises to the highest point, which is now the RIGHT flank — and you can see a crescent of air between the liver and the abdominal wall. This is an alternative when erect CXR is not possible.
If CT is available: CT is far more sensitive than plain films for detecting small amounts of free air (even tiny bubbles) and can also identify the site of perforation.
7. Blunt Abdominal Trauma
CT is the primary imaging modality of choice to evaluate haemodynamically stable patients. IV contrast (and oral contrast in conscious patient). IV contrast essential for diagnosis of visceral injuries and active arterial extravasation. [1]
Critical Distinction
CT is for haemodynamically STABLE patients. If the patient is haemodynamically unstable, do a FAST scan (Focused Assessment with Sonography in Trauma) at the bedside. If FAST is positive in an unstable patient → go straight to laparotomy. Do NOT delay by sending them to CT.
Detection of organ injury. Grading severity of injury. Prognostic criteria. ? Operative or conservative management. [1]
Modern trauma management has shifted toward non-operative management (NOM) of many solid organ injuries (liver, spleen, kidney) in stable patients. CT grading (e.g., AAST grading) determines which patients can be managed conservatively and which need surgery or angioembolization.
From the surgery notes [5]:
- Arterial phase: Identifies active bleeding points and pseudoaneurysms
- Portal venous phase (most important): Best for assessing visceral injury
- Delayed phase: Identifies urinary extravasation (renal/bladder injury)
- Bone and lung windows: For rib fractures, pneumothorax, vertebral fractures
| Organ | CT Findings | Clinical Notes |
|---|---|---|
| Spleen | Subcapsular and intraparenchymal haematomas, lacerations, fractures, vascular pedicle injury [1] | Most commonly injured solid organ in blunt abdominal trauma; delayed rupture possible [5] |
| Liver | Liver lacerations, contusion and subcapsular haematoma [1] | Second most commonly injured; associated with right lower rib fractures |
| Kidney | Pre- and post-contrast images show haemorrhage, parenchymal laceration, large haematoma extending to anterior and posterior pararenal space [1]; "Shattered kidney" [1] | Delayed phase essential to check for urinary extravasation |
| Ribs | Multiple left lower rib fractures [1] | Left lower rib fractures → suspect splenic injury; right lower → suspect liver injury |
The FAST scan (Focused Assessment with Sonography in Trauma) is a bedside ultrasound protocol [5]:
| View | Looks For |
|---|---|
| Pericardial (subxiphoid) | Pericardial effusion / tamponade |
| RUQ (Morrison's pouch) | Hepatorenal free fluid, right subphrenic fluid, right pleural fluid |
| LUQ (splenorenal) | Splenorenal free fluid, left subphrenic fluid, left pleural fluid |
| Pelvis (suprapubic) | Free fluid in Pouch of Douglas (female) / rectovesical space (male) |
Positive FAST in unstable patient → laparotomy Negative FAST does NOT rule out injury (sensitivity ~85% for free fluid; misses retroperitoneal injuries, small amounts of fluid, and solid organ injuries without significant haemoperitoneum)
8. Right Lower Quadrant Pain — Acute Appendicitis
Imaging to reduce negative appendectomy rate. Atypical signs and symptoms. [1]
Historically, surgeons operated on clinical suspicion alone, leading to negative appendectomy rates of 15–25%. Imaging has reduced this to < 5%.
Ultrasonography or CT: institutional preference and local expertise. CT — obese patients and suspected perforation. US — pediatric, pregnant, women with normal body habitus. [1]
| Modality | Best For | Findings |
|---|---|---|
| Ultrasound | Children, pregnant women, thin patients | Blind pouch, no peristalsis, > 6mm AP diameter, appendicolith, periappendiceal abscess [1] |
| CT | Obese patients, suspected perforation, equivocal US | > 6mm AP diameter, periappendiceal inflammation (may be done without oral or IV contrast) [1] |
The key number is > 6mm AP diameter — this threshold applies to both US and CT.
Past Paper Alert
2016 SAQ Q9: 7-year-old boy with RLQ pain and fever. Asked for: (a) diagnosis [acute appendicitis], (b) most appropriate imaging modality and 3 reasons [US — no radiation, good for pediatric, readily available, no contrast needed], (c) imaging findings [> 6mm diameter, appendicolith, non-compressible blind-ending tube], (d) alternative cross-sectional modality in obese child [CT]. [6]
9. Hypotension and Abdominal Pain — Ruptured AAA
Abdominal or back pain, tender abdominal mass and hypotension. Nearly 100% mortality rate if surgery is not performed urgently. [1]
This is a surgical emergency. The classic triad is: abdominal/back pain + pulsatile abdominal mass + hypotension. If all three are present, the patient goes to theatre without imaging.
If imaging is not immediately available, patient taken to surgery. [1] Immediate non-contrast CT makes diagnosis; if time allows, IV contrast is helpful. [1]
| Modality | Role | Key Points |
|---|---|---|
| Non-contrast CT | Extraluminal retroperitoneal blood [1] | Fast diagnosis; high-density blood in retroperitoneum around aorta |
| Contrast-enhanced CT | Active bleeding from aortic aneurysm into retroperitoneum — focal dense collection of contrast-enhanced blood [1] | Shows active extravasation site; helps plan surgery/EVAR |
| Ultrasound | Screening of suspected abdominal aneurysm in asymptomatic patient but limited in ability to delineate extent [1] | Good for screening/surveillance (NHS screening programme); poor in emergency (gas, body habitus, cannot show leak) |
Past Paper Alert
2017 SAQ Q6: 65-year-old man with sudden abdominal/back pain, BP 90/40, tender expansile abdominal mass. Asked: (a) diagnosis [ruptured AAA], (b) CT features [retroperitoneal haematoma, dilated aorta with calcified wall, active contrast extravasation], (c) surgical treatments [open repair or EVAR]. [7]
Mostly arteriosclerotic; others: mycotic and pseudoaneurysms [1]
- Atherosclerotic: Most common (> 90%); infrarenal > suprarenal
- Mycotic: Infected aneurysm (salmonella, staphylococcus); irregular, saccular, rapidly expanding
- Pseudoaneurysm: Wall defect with contained rupture; all layers disrupted
10. Acute Scrotal Pain — Testicular Torsion
Testicular torsion / torsion of the appendix testis. Acute epididymitis / epididymo-orchitis. Incarcerated inguinal hernia. Testicular trauma. [1]
If untreated, testicular necrosis can occur within 6 hours after the onset of symptoms. [1]
High Yield: Clinical vs Imaging Decision
Clinically, if there is reasonable likelihood of torsion, patient should be brought to surgery without delay. [1]
This is the KEY teaching point: Do NOT delay surgery for imaging if clinical suspicion is high. The 6-hour window is critical. Imaging is useful when the diagnosis is uncertain (e.g., differentiating torsion from epididymitis), but should NOT delay surgical exploration when torsion is the leading diagnosis.
| Clinical Scenario | First-Line Imaging | Second-Line / Alternative | Key Reason |
|---|---|---|---|
| Head trauma | Non-contrast CT brain | MRI (for DAI, post-traumatic syndrome) | Fast, detects haemorrhage + fractures |
| CNS infection | CT or MRI with IV contrast (before LP) | MRI preferred if available | Exclude mass before LP; detect abscess/empyema |
| Cord compression | MRI spine | CT myelography if MRI contraindicated | Only modality that directly visualizes cord |
| PE | CXR → CTPA | V/Q scan (if contrast CI), DVT US (pregnancy) | Fast, high sensitivity and specificity |
| DVT | Compression US with Doppler | CT venography, MR venography | Non-invasive, high accuracy proximal to calf |
| Pneumoperitoneum | Erect CXR | Left lateral decubitus AXR (if cannot stand); CT | CXR shows subdiaphragmatic air |
| Blunt abdominal trauma | CT with IV contrast (stable) / FAST (unstable) | Diagnostic peritoneal lavage (rarely used now) | CT grades injury; FAST is bedside triage |
| Appendicitis | US (children, thin, pregnant) or CT (obese, perforation) | MRI (pregnancy, equivocal) | US: no radiation; CT: better in obese |
| Ruptured AAA | Non-contrast CT → CECT if time | US for screening only | CT shows retroperitoneal blood |
| Testicular torsion | Doppler US | Clinical decision → theatre | Shows absent flow; but don't delay surgery |
| Cervical spine trauma | Plain XR → CT (bone) → MRI (cord) | CT upfront in high-energy trauma | Must visualize all 7 vertebrae + C7/T1 |
12. Integration with Related Material
- CXR: Widened mediastinum (but non-specific — also seen in elderly patients with mediastinal fat)
- Gold standard: CT aortogram (pre- and post-contrast)
- False lumen: Usually larger, may contain thrombus
- Stanford classification: Type A (ascending aorta involvement — surgical emergency) vs Type B (descending only — usually medical management) [8]
- First-line: Plain CT brain (to exclude haemorrhage before thrombolysis)
- Follow-up: CT angiography (CTA) or MR angiography (MRA) to identify the occluded vessel
- 2021 SAQ Q8: 65-year-old with AF and left hemiplegia → plain CT brain → look for hyperdense MCA sign → CTA/MRA → IV tPA if within time window
- Clinical diagnosis → immediate needle decompression (do NOT delay for CXR)
- Signs: respiratory distress, tracheal deviation, hyper-resonance, absent breath sounds, distended neck veins, hypotension
- 2025 MCQ Q72: Answer is needle decompression, NOT CXR
- 2025 MCQ Q61: Metastatic lung cancer with back pain and lower limb weakness → start high-dose steroids and arrange urgent orthopaedic consultation for decompressive surgery (not PET scan or bone scan first)
13. Likely Exam Questions
- Best imaging modality for acute head injury? → Non-contrast CT brain [1]
- Best imaging modality for suspected PE when eGFR < 30? → V/Q scan [2]
- Best imaging modality for testicular torsion? → Doppler ultrasound of testis [1]
- Best imaging to detect pneumoperitoneum? → Erect CXR [1]
- Best modality for cord compression? → MRI spine [1]
- First-line imaging in stable blunt abdominal trauma? → CT with IV contrast [1]
- Best screening modality for AAA? → Ultrasound [1]
-
A 65-year-old man presents with sudden abdominal pain, back pain, BP 90/40, pulsatile abdominal mass. (a) Most likely diagnosis? (b) Best imaging and findings? (c) Management?
- (a) Ruptured abdominal aortic aneurysm
- (b) Non-contrast CT → dilated aorta, retroperitoneal haematoma; CECT → active contrast extravasation
- (c) Emergency surgical repair (open or EVAR); resuscitate with fluids/blood
-
A 7-year-old child with RLQ pain and fever. (a) Diagnosis? (b) Best imaging and reasons? (c) Imaging findings?
- (a) Acute appendicitis
- (b) Ultrasound — no radiation (paediatric), no contrast needed, readily available, good sensitivity in thin children
- (c) Non-compressible blind-ending tube > 6mm, appendicolith, periappendiceal fluid/abscess
-
A patient with sudden onset SOB and pleuritic chest pain. What imaging would you request and why?
- CXR first (to exclude other causes), then CTPA (to confirm PE — shows intraluminal filling defect in pulmonary arteries)
-
When should you NOT delay for imaging? Give two examples.
- (1) Testicular torsion with high clinical suspicion → straight to theatre
- (2) Tension pneumothorax → needle decompression before CXR
- (3) Ruptured AAA when imaging not immediately available → straight to OR
Active Recall - Emergency Radiology
High Yield Summary
Emergency Radiology Core Principles:
- ABCDE first — stabilise the patient before imaging. Never let imaging delay life-saving treatment.
- Head trauma → Non-contrast CT brain (sufficiently diagnostic to end workup in most cases). SXR is generally useless. MRI is NOT first-line.
- CNS infection → Image before LP (CT or MRI with IV contrast) to exclude mass/raised ICP. LP remains the gold standard for meningitis diagnosis.
- Cord compression → MRI spine (emergency — treat with high-dose steroids while arranging imaging). C-spine trauma: plain XR → CT (bone) → MRI (cord).
- PE → CXR then CTPA. If contrast contraindicated → V/Q scan or DVT US. CTPA sensitivity 82–94%, specificity 78–95%. V/Q high probability: specificity 97%.
- DVT → Compression US with Doppler (sensitivity 95%, specificity 98% excluding calf veins).
- Pneumoperitoneum → Erect CXR (NOT erect AXR). Left lateral decubitus AXR for immobile patients.
- Blunt abdominal trauma → CT with IV contrast (stable patients). FAST for unstable patients → positive FAST + unstable = laparotomy.
- Appendicitis → US (paediatric/pregnant/thin) or CT (obese/perforation). Key threshold: > 6mm AP diameter.
- Ruptured AAA → Non-contrast CT (retroperitoneal blood). If imaging unavailable, go straight to OR. Nearly 100% mortality without surgery.
- Testicular torsion → Doppler US (absent arterial flow). But if clinical suspicion is high, go to surgery — don't wait for imaging. Necrosis within 6 hours.
- Radiologist = team member → Communicate findings verbally AND in writing. Tailor examination to clinical question.
[1] Lecture slides: GC 013. Emergency radiology.pdf (all pages) [2] Senior notes: Block A - Chest Pain - Department of Radiology.pdf (p1) [3] Senior notes: Ryan Ho Diagnostic Radiology.pdf (p5, p36); Ryan Ho Fundamentals.pdf (p337) [4] Senior notes: Ryan Ho Neurology.pdf (p197, p202) [5] Senior notes: Maksim Surgery Notes.pdf (p42) [6] Past papers: 2016 Fourth Summative SAQ.pdf (Q9, p5) [7] Past papers: 2017 Fourth Summative SAQ.pdf (Q6, p3) [8] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p604) [9] Past papers: 2021 Fourth Summative SAQ.pdf (Q8, p9); 2022 Fourth Summative SAQ.pdf (Q1, p2) [10] Past papers: 2025 Fourth Summative MCQ.pdf (Q61, p24; Q72, p27)
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