Tag Archives: radiology


Is it time to abandon plain radiography in the trauma room?

For patients who will be having a chest CT, perhaps sonography could replace chest radiography in the resus room as the initial imaging step; this recent prospective study shows its superiority over the ‘traditional’ ATLS approach.

In haemodynamically stable patients with prophylactic pelvic splints in place, one could easily argue against plain pelvis films too (the caveat being rapid access to CT is necessary). The arguments against resus-room lateral cervical spine x-rays were made ages ago and these are now rarely done in the UK & Australia.

Is it time to abandon plain radiography altogether for stable major trauma patients?


Background: The accuracy of combined clinical examination (CE) and chest radiography (CXR) (CE + CXR) vs thoracic ultrasonography in the acute assessment of pneumothorax, hemothorax, and lung contusion in chest trauma patients is unknown.

Methods: We conducted a prospective, observational cohort study involving 119 adult patients admitted to the ED with thoracic trauma. Each patient, secured onto a vacuum mattress, underwent a subsequent thoracic CT scan after first receiving CE, CXR, and thoracic ultrasonography. The diagnostic performance of each method was also evaluated in a subgroup of 35 patients with hemodynamic and/or respiratory instability.

Results: Of the 237 lung fields included in the study, we observed 53 pneumothoraces, 35 hemothoraces, and 147 lung contusions, according to either thoracic CT scan or thoracic decompression if placed before the CT scan. The diagnostic performance of ultrasonography was higher than that of CE + CXR, as shown by their respective areas under the receiver operating characteristic curves (AUC-ROC): mean 0.75 (95% CI, 0.67-0.83) vs 0.62 (0.54-0.70) in pneumothorax cases and 0.73 (0.67-0.80) vs 0.66 (0.61-0.72) for lung contusions, respectively (all P < .05). In addition, the diagnostic performance of ultrasonography to detect pneumothorax was enhanced in the most severely injured patients: 0.86 (0.73-0.98) vs 0.70 (0.61-0.80) with CE + CXR. No difference between modalities was found for hemothorax.


Conclusions: Thoracic ultrasonography as a bedside diagnostic modality is a better diagnostic test than CE and CXR in comparison with CT scanning when evaluating supine chest trauma patients in the emergency setting, particularly for diagnosing pneumothoraces and lung contusions.

Diagnostic accuracy of ultrasonography in the acute assessment of common thoracic lesions after trauma
Chest. 2012 May;141(5):1177-83

Spinal imaging for the adult obtunded blunt trauma patient

‘You can’t clear the cervical spine until the patient wakes up!’ How often have you heard this said about a patient with severe traumatic brain injury who may not ‘wake up’ for weeks, if at all?

A controversial area, but many institutions now allow collar removal if a neck CT scan is normal. Does this rule out injury with 100% sensitivity? No – but it probably pushes the balance of risk towards removing the collar – an intervention with no evidence for benefit and plenty of reasons why it may be harmful to ventilated ICU patients. For example, clearing the cervical spine based on MDCT was associated with less delirium and less ventilator associated pneumonia, both of which have been associated with increased mortality in critically ill patients (this is referenced in the paper below).

The UK’s Intensive Care Society has had pragmatic guidelines along these lines since 2005, which can be found here. This month’s Intensive Care Medicine publishes an updated literature review providing some further support to this approach.



PURPOSE: Controversy exists over how to ‘clear’ (we mean enable the clinician to safely remove spinal precautions based on imaging and/or clinical examination) the spine of significant unstable injury among clinically unevaluable obtunded blunt trauma patients (OBTPs). This review provides a clinically relevant update of the available evidence since our last review and practice recommendations in 2004.


METHODS: Medline, Embase. Google Scholar, BestBETs, the trip database, BMJ clinical evidence and the Cochrane library were searched. Bibliographies of relevant studies were reviewed.


RESULTS: Plain radiography has low sensitivity for detecting unstable spinal injuries in OBTPs whereas multidetector-row computerised tomography (MDCT) approaches 100%. Magnetic resonance imaging (MRI) is inferior to MDCT for detecting bony injury but superior for detecting soft tissue injury with a sensitivity approaching 100%, although 40% of such injuries may be stable and ‘false positive’. For studies comparing MDCT with MRI for OBTPs; MRI following ‘normal’ CT may detect up to 7.5% missed injuries with an operative fixation in 0.29% and prolonged collar application in 4.3%. Increasing data is available on the complications associated with prolonged spinal immobilisation among a population where a minority have an actual injury.


CONCLUSIONS: Given the variability of screening performance it remains acceptable for clinicians to clear the spine of OBTPs using MDCT alone or MDCT followed by MRI, with implications to either approach. Ongoing research is needed and suggestions are made regarding this. It is essential clinicians and institutions audit their data to determine their likely screening performances in practice.


Clinical review: spinal imaging for the adult obtunded blunt trauma patient: update from 2004
Intensive Care Med. 2012 Mar 10. [Epub ahead of print]

Ultrasound for pneumonia

Lung ultrasound done by a single keen individual had better test characteristics than CXR in diagnosing pneumonia as defined by discharge diagnosis.
The lung ultrasound was considered to be positive for pneumonia if it showed consolidation (including air bronchograms) or a focal interstitial syndrome (localised increased density of ‘B’ lines)



Objective The aim of this study was to evaluate the diagnostic accuracy of bedside lung ultrasound and chest radiography (CXR) in patients with suspected pneumonia compared with CT scan and final diagnosis at discharge.


Design A prospective clinical study.


Methods Lung ultrasound and CXR were performed in sequence in adult patients admitted to the emergency department (ED) for suspected pneumonia. A chest CT scan was performed during hospital stay when clinically indicated.


Results 120 patients entered the study. A discharge diagnosis of pneumonia was confirmed in 81 (67.5%). The first CXR was positive in 54/81 patients (sensitivity 67%; 95% CI 56.4% to 76.9%) and negative in 33/39 (specificity 85%; 95% CI 73.3% to 95.9%), whereas lung ultrasound was positive in 80/81 (sensitivity 98%; 95% CI 93.3% to 99.9%) and negative in 37/39 (specificity 95%; 95% CI 82.7% to 99.4%). A CT scan was performed in 30 patients (26 of which were positive for pneumonia); in this subgroup the first CXR was diagnostic for pneumonia in 18/26 cases (sensitivity 69%), whereas ultrasound was positive in 25/26 (sensitivity 96%). The feasibility of ultrasound was 100% and the examination was always performed in less than 5 min.


Conclusions Bedside chest ultrasound is a reliable tool for the diagnosis of pneumonia in the ED, probably being superior to CXR in this setting. It is likely that its wider use will allow a faster diagnosis, conducive to a more appropriate and timely therapy.


Lung ultrasound is an accurate diagnostic tool for the diagnosis of pneumonia in the emergency department
Emerg Med J. 2012 Jan;29(1):19-23

Offensive medicine: CT before LP

I’m getting worn down by clinicians – often other specialists – who insist that CT imaging of the brain is mandatory prior to lumbar puncture in all patients. There is surely a subgroup of patients (especially young ones) in whom the benefit:harm balance of CT comes out in favour of NOT doing the imaging. In these cases, getting the scan is not ‘defensive medicine’ but ‘offensive medicine’ – offending the principle of primum non nocere. During ED shifts I have recently had to perform online searches in order to furnish colleagues and patients’ medically qualified relatives with printouts of the literature on this. This page is here to save me having to repeat those searches. Regarding the practice of performing a routine head CT prior to lumbar puncture to rule out risk of herniation:

  • Mass effect on CT does not predict herniation
  • Lack of mass effect on CT does not rule out raised ICP or herniation
  • Herniation has occurred in patients who did not undergoing lumbar puncture because of CT findings
  • Clinical predictors of raised ICP are more reliable than CT findings
  • CT may delay diagnosis and treatment of meningitis
  • Even in patients in whom LP may be considered contraindicated (cerebral abscess, mass effect on CT), complications from LP were rare in several studies

Best practice, it would seem, is the following

  • If you think CT will show a cause for the headache, do a CT
  • If a CT is indicated for other reasons (depressed conscious level, focal neurology), do a CT
  • If a GCS 15 patient is to undergo LP for suspected (or to rule out) meningitis, and they have a normal neurological exam (including fundi), and are not elderly or immunosuppressed, there is no need to do a CT first.
  • If you’re seriously worried about meningitis and are intent on getting a CT prior to LP, don’t let the imaging delay antimicrobial therapy.

Here are some useful references:

1. The CT doesn’t help

CT head before lumbar puncture in suspected meningitis BestBET evidence summary: In cases of suspected meningitis it is very unlikely that patients without clinical risk factors (immunocompromise/ history of CNS disease/seizures) or positive neurological findings will have a contraindication to lumbar puncture on their CT scan If CT scan is deemed to be necessary, administration of antibiotics should not be delayed. BestBETS website Computed Tomography of the Head before Lumbar Puncture in Adults with Suspected Meningitis Much cited NEJM paper from 2001 which concludes: “In adults with suspected meningitis, clinical features can be used to identify those who are unlikely to have abnormal findings on CT of the headN Engl J Med. 2001 Dec 13;345(24):1727-33 Full Text Cranial CT before Lumbar Puncture in Suspected Meningitis Correspondence in 2002 NEJM including study of 75 patients with pneumococcal meningitis: CT cannot rule out risk of herniation Cranial CT before Lumbar Puncture in Suspected Meningitis N Engl J Med. 2002 Apr 18;346(16):1248-51 Full Text

 

2. The CT may harm

Cancer risk from CT Paucis verbis card, from the wonderful Academic Life in EM

 

3. Guidelines say CT is not always needed

National (UK) guidelines on meningitis (community acquired meningitis in the immunocompetent host) available from meningitis.org. This PDF poster clearly outlines limitations of head CT, and includes this box:

Practice Guidelines for the Management of Bacterial Meningitis These 2004 guidelines from the Infectious Diseases Society of America provide the following table listing the recommended criteria for adult patients with suspected bacterial meningitis who should undergo CT prior to lumbar puncture: Clin Infect Dis. (2004) 39 (9): 1267-1284 Full text

 

4. This is potentially even more of an issue with paediatric patients

Fatal Lumbar Puncture: Fact Versus Fiction—An Approach to a Clinical Dilemma An excellent summary of the above mentioned issues presented in a paediatric context, including the following:

On initial consideration a cranial CT would seem to be an appropriate and potentially useful diagnostic study for confirming the diagnosis of cerebral herniataion. The fallacy in this assessment has been emphasized by the finding that no clinically significant CT abnormalities are found that are not suspected on clinical assessments. Further, as previously noted, a normal CT examination may be found at about the time of a fatal herniation. Thus, the practical usefulness of a cranial CT in the majority of pediatric patients is limited to those rare patients whose increased ICP is secondary to mass lesions, not in the initial approach to acute meningitis.

Pediatrics. 2003 Sep;112(3 Pt 1):e174-6 Full Text

 

The last words should go to Dr Brad Spellberg, who in response to the IDSA’s guidelines wrote an excellent letter summarising much of the evidence at the time, confessed:

Why do we persist in using the CT scan for this purpose, despite the lack of supportive data? I am as guilty of this practice as anyone else, and the reason is simple: I am a chicken.

Clin Infect Dis. (2005) 40 (7): 1061 Full Text

UK Radiology guidelines for trauma

The Royal College of Radiologists in the UK has published a guideline document to set standards related to diagnostic and interventional radiology for use by major trauma centres (MTCs) and trauma units (TUs). The standards are:

  1. The trauma team leader is in overall charge in acute care
  2. Protocol-driven imaging and intervention must be available and delivered by experienced staff. Acute care for SIPs must be consultant delivered
  3. MDCT should be adjacent to, or in, the emergency room
  4. Digital radiography must be available in the emergency room
  5. If there is an early decision to request MDCT, FAST and DR should not cause any delay
  6. MRI must be available with safe access for the SIP
  7. A CT request in the trauma setting should comply with the Ionising Radiation (Medical Exposure) Regulations 2000 (IR(ME)R) justification regulations like any other request for imaging involving ionising radiation
  8. There should be clear written protocols for MDCT preparation and transfer to the scan room
  9. Whole-body contrast-enhanced MDCT is the default imaging procedure of choice in the SIP. Imaging protocols should be clearly defined and uniform across a regional trauma network
  10. Future planning and design of emergency rooms should concentrate on increasing the numbers of SIPs stable enough for MDCT and intervention
  11. The primary survey report should be issued immediately to the trauma team leader
  12. On-call consultant radiologists should provide the final report on the SIP within one hour of MDCT image acquisition
  13. On-call consultant radiologists must have teleradiology facilities at home that allow accurate reports to be issued within one hour of MDCT image acquisition
  14. IR facilities should be co-located to the emergency department
  15. Angiographic facilities and endovascular theatres in MTCs should be safe environments for SIPs and should be of theatre standard
  16. Agreed written transfer protocols between the emergency department and imaging/interventional facilities internally or externally must be available
  17. IR trauma teams should be in place within 60 minutes of the patient’s admission or 30 minutes of referral
  18. Any deficiency in consumable equipment should be reported at the debriefing and be the subject of an incident report

Some interesting snippets include:
IV access
Right antecubital access is preferred for contrast administration (left-sided injections compromise interpretation of mediastinal vasculature). However, if arm vein access is not possible and a central line is in situ, it should be of a type that can accept 4 ml contrast/ second via a power injector. This might require local negotiation with emergency department doctors beforehand

Pelvic fracture
If a pelvic fracture is suspected, a temporary pelvic stabilisation (wrap, binder and so on) should be applied before MDCT.

Limb fractures
Rapid immobilisation such as air splints. Only immediately limb conserving manipulations/splinting should be performed prior to CT.

Urinary catheter
All significantly injured patients without obvious contraindications should be catheterised unless this would delay transfer to CT. The catheter should be clamped prior to MDCT.

Standards of practice and guidance for trauma radiology in severely injured patients
Royal College of Radiologists – Full Text Link

Algorithm for Body Packers

‘Mules’ or body packers are people who transport illegal drugs by packet ingestion into the gastrointestinal tract. A large study of body packers apprehended by United State Customs officials at JFK International Airport, New York describes experience with body packers and an algorithm for conservative and surgical management.

Of 56 patients requiring admission out of a total of 1250 subjects confirmed to be body packers, 25 patients (45%) required surgical intervention, whereas 31 patients (55%) were successfully managed conservatively.

Diagnosis:

  • Plain abdominal x-ray was diagnostic in 49 patients (88% of all hospitalised patients).
  • Non-contrast CT of the abdomen and pelvis is required if AXR is negative
  • Forty-eight per cent of body packers had positive urine toxicology for illicit substances.

Management:

  • Indications for intervention included:
  • bowel obstruction
  • packet rupture/toxicity
  • delayed progression of packet transit on conservative management.
  • Patients with packets found predominantly in the proximal gastrointestinal tract failed conservative management more frequently than those with packets found in the distal gastrointestinal tract.

Multiple intraoperative manoeuvres were used to remove the foreign bodies:

  • gastrotomy
  • enterotomy
  • colotomy.

Wound infection was the most common complication and is associated with distal enterotomy and colotomy.

The authors recommend a confirmatory radiological study to demonstrate complete clearance of packets

Establishment of a definitive protocol for the diagnosis and management of body packers (drug mules).
Emerg Med J 2011;28:98-10

Missed PTX signs on CXR

Chest x-rays often miss pneumothoraces in the trauma room. These are occult pneumothoraces. A study using agreement by two fellowship trained radiologists as the gold standard for CXR interpretation showed that 80% of these were truly occult, ie. not detectable by the radiologists from CXR and only demonstrable on CT. Of those seven cases that could or should have been identified by emergency physicians (ie. ‘missed’ pneumothoraces) subcutaneous emphysema (5), pleural line (3), and deep sulcus sign (2) were detected by the radiologist reviewers.

This serves both as a reminder of the signs to look for on CXR for pneumothorax, and of the inadequacy of plain radiography in trauma patients. The authors advise in their discussion that  ‘Thoracic ultrasonography may be the ideal diagnostic modality as it has a high sensitivity for the detection of PTX and it may be performed quickly at the bedside while maintaining spinal precautions’.

If you don’t know how to detect a pneumothorax with ultrasound yet, have a look here.

Occult Pneumothoraces Truly Occult or Simply Missed: Redux
J Trauma. 2010 Dec;69(6):1335-7

Flat IVC on CT associated with deterioration

BACKGROUND: : We aimed to investigate the value of the diameter of the inferior vena cava (IVC) on initial computed tomography (CT) to predict hemodynamic deterioration in patients with blunt torso trauma.

METHODS: : We reviewed the initial CT scans, taken after admission to emergency room (ER), of 114 patients with blunt torso trauma who were consecutively admitted during a 24-month period. We measured the maximal anteroposterior and transverse diameters of the IVC at the level of the renal vein. Flat vena cava (FVC) was defined as a maximal transverse to anteroposterior ratio of less than 4:1. According to the hemodynamic status, the patients were categorized into three groups. Patients with hemodynamic deterioration after the CT scans were defined as group D (n = 37). The other patients who remained hemodynamically stable after the CT scans were divided into two groups: patients who were hemodynamically stable on ER arrival were defined as group S (n = 60) and those who were in shock on ER arrival and responded to the fluid resuscitation were defined as group R (n = 17).

RESULTS: : The anteroposterior diameter of the IVC in group D was significantly smaller than those in groups R and S (7.6 mm ± 4.4 mm, 15.8 mm ± 5.5 mm, and 15.3 mm ± 4.2 mm, respectively; p < 0.05). Of the 93 patients without FVC, 16 (17%) were in group D, 14 (15%) required blood transfusion, and 8 (9%) required intervention. However, of the 21 patients with FVC, all patients were in group D, 20 (95%) required blood transfusion, and 17 (80%) required intervention. The patients with FVC had higher mortality (52%) than the other patients (2%).

CONCLUSION: : In cases of blunt torso trauma, patients with FVC on initial CT may exhibit hemodynamic deterioration, necessitating early blood transfusion and therapeutic intervention.

Predictive Value of a Flat Inferior Vena Cava on Initial Computed Tomography for Hemodynamic Deterioration in Patients With Blunt Torso Trauma
J Trauma. 2010 Dec;69(6):1398-402

MRA for PE not very good

Wouldn’t it be great to have a reliable, radiation-free way to diagnose pulmonary embolism? Unfortunately, Magnetic Resonance Angiography is not it. In a study of 371 patients across 7 hospitals from the PIOPED III (Prospective Investigation of Pulmonary Embolism Diagnosis III) investigators, the test was technically inadequate because of poor-quality images in 25% of cases. In those tests that were readable, the sensitivity was only 78%.

Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: A Multicenter Prospective Study (PIOPED III)
Ann Intern Med. 2010 Apr 6;152(7):434-43