Answer: Right hilar lung cancer

The key to this case is in comparing the hilar structures – there are three things I look for when looking at the hilar regions:

1. Position
2. Density
3. Morphology

In this case the right hilum is clearly more dense than the left (ie it the shade of grey is much brighter) whilst also the morphology is different. Whereas the left the hilum has the shape of branching vessels, the right side is much larger and lobulated.

A dense hilum should ring alarm bells and make you think that there could be either underlying lymph node enlargement (could be related to TB, lymphoma, sarcoid) or a malignant mass (usually a primary lung cancer).

The abnormality doesn’t end there though – look closely and you’ll see there is an extra structure to the right of the right hilum. This is a key review area – lesions adjacent to the hilum are often missed.

When we compare to a subsequent CT scan we can see that the extra mass relates to a mass adjacent to the hilum (yellow arrows) whereas the dense hilum is secondary to enlarged lymph nodes at the right hilum (white arrows).

The mass was subsequently biopsied and was confirmed as a primary lung cancer. As there are right hilar nodes the nodal staging (TNM classification) relates to N1. Although a pneumonia with enlarged reactive hilar nodes was possible here, the history of weight loss should put lung cancer to the top of the differential here.

Learning point

On every chest X-Ray you assess, make sure you assess the hilar regions for position, morphology and density.

Answer: Loss of left insula ribbon and acute left MCA infarct

This case highlights an important review area on CT head scans – the insular cortex. As a grey matter structure the insula should be brighter than white matter structures – for example the neighbouring internal capsule. Have a look at the right side – this is normal in that the insula is brighter than the internal capsule. Things are different on the left side however as we cannot say the same thing.

In the event of a middle cerebral artery (MCA) occlusion, the insula cortex receives less blood supply from anterior and posterior cerebral artery circulation and therefore abnormalities of the insula can be one of the earliest signs of acute MCA stroke.

In cases of suspected ischaemic stroke that are elegible for thrombectomy, a CT angiogram can be performed – here we give intravenous contrast and the vessels show up as bright. We are looking for filling defects within the vessels – below we have images from the CT angiogram in this case.

The angiogram confirms an acute MCA stroke. Sometimes ischaemic stroke can present in atypical fashion so recognising the loss of the insula ribbon becomes even more important. I make it a point to look for it on every acute CT head I look at!

Learning point

Loss of the insula ribbon can be the only abnormality on a CT head scan and can be the only pointer towards a diagnosis of acute MCA stroke.

Answer: Second toe PIPJ subluxation

The key to this case is in remembering to check the alignment of all toes and fingers. Here the second toe PIPJ is subluxed (ie partially dislocated).

Subtle subluxations can be tricky to catch. Of course picking this out of an X-ray is easier when the patient is in front of you pointing right at the culprit however things aren’t always that straightforward.

Compare the appearance with the post relocation film where the PIPJ is no longer subluxed…

Learning point

Remember to check the alignment of the toes on foot X-rays – subluxation can be subtle.

Answer: Proximal humerus fracture and anterior glenohumeral dislocation

The first issue here is to notice that the proximal humerus is fractured – we can see the greater tuberosity has completely come apart from the humeral head! This means there has been a displaced fracture.

It is important not to stop there – as always it’s important to follow your normal review patterns. On all shoulder X-rays alignment of the glenohumeral joint should always be high up on your list of things to check. Try and outline the glenoid which is part of the scapula and on an AP view is ‘oval shaped’. Look to see if the humeral head lines up with this and sits next to the ‘oval’...

In our case we can see the humeral head has come away from the glenoid and looks like it has moved towards the ribs. This is typical for an anterior dislocation. Have a look at the post surgical film below- the humerus now sits next to the glenoid.

It is usual practice to look to try and get two views of the shoulder in cases of trauma although that can be tricky if the patient is in a lot of pain. There are different options for the supplementary view to the AP, with commonly used views including the ‘Y view’ and the ‘modified axial view’.

Posterior dislocations can be a lot more challenging to diagnose on X-ray. These are less common and are classically associated with seizures given the shoulder is pushed posteriorly in internal rotation whilst the arm is abducted. On X-ray here you are looking for a ‘lightbulb’ appearance of the humeral head.

Learning point

Remember to check the alignment of the glenohumeral joint on every shoulder film you look at.

Answer: Colloid cyst with acute hydrocephalus

Here we have two axial images from an MRI head (FLAIR sequence). On the top image we can see the lateral ventricles – we can see they are both dilated.

When we see this it is important to look for a source of obstruction. The second image shows us an axial slice slightly more inferiorly. We can just about make out the lateral ventricles as they connect with the centrally located third ventricle via the foramen of Monro. 

Here we can see there is a well defined lesion within the third ventricle in the region of the foramen of Monro – this is our culprit.

This is the typical location and appearance of a colloid cyst – this was confirmed after surgery. What is a colloid cyst?

Did you spot the high FLAIR signal surrounding the lateral ventricles?

This represents transependymal oedema and is a sign of acute hydrocephalus – the ventricular ependymal lining is disrupted allowing migration of CSF into the periventricular white matter. It is important to look for this if we suspect the ventricles are dilated.

Learning point

When you see dilated ventricles on brain imaging follow the CSF spaces and try to find the source of obstruction.

Answer: Obstructing left distal ureteric calculus

Here we have a CT KUB, a commonly performed study in Emergency Departments all around the world looking for renal calculi and its consequences. A lot of departments perform these with the patient on their front (prone rather than supine): this helps in cases where it is hard to differentiate whether a calculus lies within the bladder or the vesico-ureteric junction (VUJ). In cases where the stone lies in the bladder the calculus will fall and be seen in a dependent position, unlike a VUJ stone.

These scans are done without contrast as the presence of bright contrast could mask stones which usually look bright on a non contrast CT.

In this case the left renal pelvis is dilated, ie there is hydronephrosis. As soon as you see this in the context of renal colic it is pretty likely there is an obstructing stone, however remember there are other causes of obstruction eg intrinsic tumour (TCC), lymph nodes compressing the ureter and clot. In any CT KUB it is important to follow the renal pelvis down to the ureter then try and track its course in front of the psoas muscle into the pelvis.

In this case when we follow the ureter to its distal third we find a bright calculus which accounts for the obstruction.

Sometimes calcified phleboliths which lie in blood vessels can cause confusion and can be mistaken for calculi – this is why it is really important to familiarise yourself with the normal course of the ureter which usually pass in front of the psoas and insert posteriorly into the bladder.

Learning point

Be methodical in following the ureter in any CT KUB study: hydronephrosis and perinephric stranding should alert you to a possible obstructing stone.

Answer: Fifth metatarsal fracture

There is a lucent line within the diaphysis of the fifth metatarsal bone with a defect within the cortex in keeping with a fracture.

It is important to trace the cortex of each and every bone you see on X-ray looking for a defect as we can see. Finding an adjacent lucent line seals the deal and tells you there has been a fracture. I haven’t been kind here and haven’t given you a second view to look at but in reality it’s really important to check at least two views when you are looking at limb X-rays in cases of trauma. Have a look at the oblique view below…

Here we can see the fracture is a lot clearer – we can see a clear break in the cortex associated with a lucent line. The fifth metatarsal is always an important review area – fractures here account for more than half of metatarsal fractures. The most common site is the base of the fifth metatarsal rather than the mid shaft as we have in this case here.

Learning point

Always pay special attention to the fifth metatarsal – fractures here account for more than half of all metatarsal fractures!

Answer: Bilateral pulmonary embolism

This is a CT of the thorax performed as a CTPA ie a CT pulmonary angiogram. Contrast is delivered ie and the scan is timed to show contrast within the pulmonary trunk and its branches.

First we need to identify the pulmonary trunk which always reminds me of an octopus although it has nowhere near 8 legs. Once we find it we need to track its branches on both sides looking for filling defects. Lo and behold in this case we can see filling defects on both sides in keeping with pulmonary emboli.

This is technically not a ‘saddle embolism’ where a filling defect straddles both pulmonary arteries and crosses the midline. With aortic dissection we would expect to see a flap within the aorta and in pneumothorax we would see gas within the pleural space: on CT this is black without any lung markings.

Did you also spot the lung nodule? There was an underlying diagnosis of lymphoma here with the lung nodule thought to be part of the disease. The nodule is easier to spot on lung windows rather than soft tissue windows.

Learning point

Assess the pulmonary arteries on every post contrast CT you assess, even when not performed as a dedicated CTPA. Pulmonary emboli can be incidental and deadly if not picked up.

Answer: Distal radius fracture

Here we have a frontal view of a wrist X-ray – it’s important here to run your eyes along the contour of each bone. If you do so in this case you’ll find the contour of the distal radius is irregular.

Here you’ll see an irregular contour – note the sharp edge which looks like a shard of glass. Once you see something like this, you can almost be certain that there is an acute fracture. Look along this line and you’ll see an irregular lucency confirming the suspicions.

Have a look at the lateral view and the fracture is more obvious. Always try and outline the dorsal surface of the distal radius which should be nice and smooth. Here we can see a jagged edge confirming the fracture.

Learning point

Outline the contour of each bone, if you find a jagged edge with a ‘shard of glass’ appearance this almost certainly means an acute fracture.

Answer: Left basal ganglia haemorrhage with intraventricular extension

Here we have a non contrast CT head. Most acute brain CT scans are done without IV contrast. Why is that?

Acute haemorrhage on a non contrast CT shows up as bright so is easier to see without contrast. A lot of acute scans are done in the context of trauma looking for haemorrhage or are looking for acute stroke. IV contrast is used when either looking at the vessels eg an angiogram or when looking for enhancing lesions such as a malignant brain tumour or abscess. You may see these lesions without contrast (although it can be more tricky) and if there is any mass effect this will be apparent without contrast.

In this case there is a large area of ‘high attenuation’ within the left sided basal ganglia: this is acute haemorrhage. Notice how the lateral ventricle is pushed to the right side in keeping with mass effect.

Don’t stop there: one review area on acute CT head is to check the ventricles, and in particular the dependent regions, ie the posterior aspect, for blood. If you look here you will see there are high density blood products layering within the posterior aspect of the ventricles. This is called intraventricular extension which has been seen to be a poor prognostic sign.

In terms of aetiology, basal ganglia haemorrhage is usually a result of long standing hypertension with rupture of micro aneurysms (also called Charcot-Bouchard aneurysms) a common culprit.

Learning point

Remember to check the posterior aspect of the ventricles on acute brain CT: a small amount of blood within the dependent aspect of the ventricle may be the only abnormality on the scan.