Imaging the Chest Flashcards
In general, for what 3 reasons are images taken?
What should be made before asking for images?
- to confirm a clinical diagnosis / suspicion
- to rule out important diagnoses / pathologies
- to guide or evaluate management / treatment
- a differential diagnosis should be made prior to asking for images - the images will then confirm this or rule it out
For what 3 broad reasons are the lungs imaged?
- to confirm a clinical diagnosis / suspicion
- this is based on the history, clinical examination and symptoms
- to rule out important diagnoses / pathologies that could potentially cause harm to the patient if missed
- to guide or evaluate management / treatment
- e.g. antibiotic prescribing, image guidance for drain insertion, biopsy, response of pathology to treatment
What are the most commonly used imaging modalities used to evaluate the lungs?
- CXR
- CT scan
What clinical symptoms may prompt a clinician to request a CXR?
- acute onset breathlessness or first presentation of chronic / gradually increasing breathlessness
- haemoptysis
- peripheral oedema
- cough for more than 3 weeks, especially in a smoker
- productive coughing - frothy sputum, blood-stained sputum, green sputum
- sudden onset pleuritic chest pain, whether traumatic or atraumatic
- chronic chest pain (may be a symptom of pleural / rib involvement in malignancy)
- symptoms of infection in a patient whom pneumonia is suspected or there is reason to suspect patient may be immunocompromised
What reasons might there be to suspect that a patient may be immunocompromised and/or require antibiotic treatment?
- elderly patients
- institutionalised patients
- patients who have a poor cough (e.g. rib fractures or are at risk of aspiration)
- patients who are homeless, IVDUs or alcohol-dependent
What clinical signs may prompt a clinician to request a CXR?
- reduced or absent breath sounds or air entry over part of a lung
- abnormal added sounds over the chest, such as crepitations / crackles
- abnormal percussion note over the chest - dullness or hyper-resonance
- respiratory distress
What is tracheal tug?
Is this an indication for imaging the lungs?
- tracheal deviation may be a sign of tension pneumothorax
- this is a life-threatening emergency
- if tension pneumothorax is suspected, it should be treated immediately BEFORE imaging
Why are CXRs taken PA opposed to AP?
When may an AP CXR be performed?
- PA views are of higher quality and more accurately assess the heart size than AP images
- AP images cannot be used to assess the heart size as it will appear enlarged
- AP images may be used when a patient is too unwell to stand and so a PA image would not be possible
What 4 technical qualities of a CXR should be considered first?
- field
- rotation
- inspiration
- penetration
(FRIP)
How is the field of a CXR assessed?
- this should include the apices to the costophrenic angles
- the humeral heads should also be within the image
How is rotation assessed on a CXR?
- look at the medial ends of the clavicles** in relation to the **spinous processes
- the distance between the medial ends of the clavicles and the spinous process should be the same
- if there is a difference in the distance on either side, this suggests the patient is rotated
How is inspiration assessed on a CXR?
- count the rib spaces
- there should be at least 5 anterior ribs and 8-10 posterior ribs
How is penetration assessed on a CXR?
- the vertebral bodies should just be visible behind the heart
- you should be able to trace the hemidiaphragms to the vertebrae
What is indicated by the pink dotted line?
the horizontal fissure
- this is present on the right lung only
- there is no middle lobe on the left side as the heart is in the way, but a lingula is present instead
Why might the hemidiaphragms become flattened?
What other feature may be present?
- the hemidiaphragms may become flattened due to hyperinflation of the lungs in emphysema
- destruction of the internal architecture of the lungs leads to there being fewer lung markings
What is shown on this CXR?
consolidation (right upper zone)
- this could be due to pus (pneumonia), blood (haemorrhage), cells (cancer) or fluid (oedema)
- these can all appear similar, so clinical information is needed to confirm the diagnosis
- a consolidated lung contains fluid but remains the same size / volume
Does a consolidated lung change size?
How does this compare to a collapsed lung?
- a consolidated lung remains the same size
- it becomes dense as it is full of fluid and the air within the lung can no longer be seen
- the lung markings are no longer visible
- a collapsed lung shows a decrease in volume and an increased density (as there is less air within it)
What is an air bronchogram and why is this seen?
- air bronchograms are seen in consolidation
- the alveoli fill with fluid, but the bronchi do not and still contain air
- the air in the bronchi is outlined by a line caused by the presence of fluid in the alveoli
- a line is only visible when there is a change in density - fluid against air
- the air-filled bronchi (dark) are made visible by the opacification of the surrounding alveoli (grey/white)
What is meant by the silhouette sign?
- this refers to the loss of normal borders between thoracic structures
- lines between structures are not seen as the structures that are next to each other are similar densities
- this allows pathlogy to be identified if you expect to see a line (e.g. heart border) and it is not there
- usually caused by radioopaque mass that touches the border of the heart or aorta
What is shown in this CXR?
collapse (likely due to pneumothorax)
- there is loss of lung markings in the right upper zone
- this indicates that there is air present in the pleural space that is compressing the lung
- there would be absent breath sounds over the collapsed area
Why is there often reduced lung markings in a collapsed lung?
- if one lobe of the lung collapses, the other(s) will expand to fill the gap
- if one lobe collapses, there is hyperinflation of the other lobes
- there is reduced lung markings in the hyperinflated lung as the same amount of lung markings are spread over a greater space
What is shown in this image?
pleural effusion (left side)
- you cannot see the costophrenic angle (left) or the left heart border due to the presence of fluid
- there is fluid present within the pleural space
Why does another image need to be taken in cases of pleural effusion?
- the fluid within the pleural space could be hiding other pathologies, such as a mass
- the fluid needs to be drained and then another image (XR or CT) should be taken to confirm whether there is an underlying mass
What is shown in this image?
What symptoms would be expected?
pulmonary oedema
- there is hazy consolidation in the right middle lobe and the right hemidiaphragm is not visible
- fluid starts to build up in the alveoli (consolidation) then in the interstitial spaces and pleural spaces
- this would present with crackles, SOB and frothy sputum if severe
What is shown in this image?
tension pneumothorax
- there is loss of lung markings on the left side due to presence of air in the pleural space causing collapse of the lung
- there is tracheal deviation towards the right side
- in tension pneumothorax, air cannot escapse and the pressure within the thorax increases with each breath
- there would be NO tracheal deviation in a simple pneumothorax
What is shown in this image?
cavitation
- this describes a thick-walled abnormal gas-filled space
- the abnormality within the left lower zone has a relatively well defined upper margin but contains a meniscus
- it contains a meniscus as it is a cavitating lesion with fluid within it
- this is seen in tuberculosis and tumours (particularly SCC)
What is shown in this image?
multiple discreet lesions** and **tenting of the diaphragm
- these “fluffy blobs” are cancer metastases until proven otherwise
- if there are multiple lesions of different sizes in BOTH lungs, there is a high suspicion of cancer
When is CXR first-line for imaging the heart?
What signs are expected to be seen?
- CXR is first-line if heart failure is suspected
- abnormalities on CXR that suggest heart failure are:
- cardiomegaly
- splaying of the carnia & left atrial enlargement
- pulmonary oedema
- pleural effusion
- upper lobe diversion
- “bat wing” opacities
What is the ABCDE approach to features of heart failure seen on CXR?
- A - alveolar oedema
- B - kerley B lines
- C - cardiomegaly
- D - dilated upper lobe vessels
- E - pleural effusion
How can heart failure present chronically and acutely?
What often precipitates the acute heart failure presentation?
Chronic:
- increasing breathlessness and tiredness
- reduced exercise tolerance
- orthopnoea
- PND (shortness of breath during sleep)
- peripheral oedema
Acute:
- sudden onset SOB
- respiratory distress
- pale, cool and clammy
Precipitating factors:
- MI
- change in medications (or patient not taking their usual meds)
In what other situations may CT imaging be used to image the heart?
- to evaluate cardiac masses seen on echo (primary malignancies or metastases)
- to assess the pericardium
- can be used if MRI is contra-indicated
When may MRI be used to image the heart?
- can be used to assess cardiac function
- can be used to characterise masses
- MRI angiography can be used to assess the coronary vasculature
- it is useful in young people as it is non-ionising (e.g. congenital heart disease)
