The chest x-ray remains the main investigation
that we use for patients presenting with lung
disease. And it’s used basically to screen
to make sure there are no major abnormalities
of the lung.
This is a normal chest x-ray with each structures
identified. I’m not going to go through
that in turn but the important point to note
here is that the lungs look black. And that’s
because they’re full of air. And most problems
that occur that you can pick up on a chest
x-ray will cause either liquid or solid material
to occur in an area where there should be
blackness due to the lung.
So you can see this in this example here.
There’s a left pleural effusion. That’s
fluid in the pleural space. And the bottom
of the left lung is now all white as a consequence
of that fluid showing up on the x-ray.
This patient’s got an interstitial lung
disease with infiltration of the upper lobes
of their lung with sarcoid tissue. And that
shows up as not very distinct but clearly
present areas of white infiltrations in both
And this patient has a TB. And that’s affecting
the top of the right lung and, again, you
can see there’s some white shadowing there.
The main exception to the white shadowing
situation is that, if you have a pneumothorax
or a large cyst in the lung full of air, that
shows up as black tissue instead of white.
But largely what we’re looking for are areas
of increased white or grey shadowing in the
Now the CT scan is a fantastic test for providing
three-dimensional lung anatomy information.
It provides multiple slices through the lung
and allows you to assess in very great detail
the parenchymal structure, the mediastinal
structure, the bones and the joints, depending
on which setting you use. In fact, if you
inject contrast into the patient and time
it correctly, you can also delineate the pulmonary
arteries very clearly and identify pulmonary
The problem with the CT scan is that it does
require quite a substantial radiation dose
compared to a chest x-ray. It takes more time.
It requires somebody to be able to hold their
breath and not be claustrophobic. And many
patients find that very difficult. And the
contrast that is used in some CT scans can
have nephrotoxic problems. It can cause or
precipitate renal failure, for example, and
it can cause exacerbations of asthma in susceptible
The CT scan though is now an established method
of assessing lung diseases of a specific type.
So, for example, if you suspect somebody has
a lung tumour, then the CT scan is absolutely
important. If you suspect they have interstitial
lung disease, again the CT scan is vital.
Pulmonary emboli: the main method of identifying
those nowadays is a CT pulmonary angiogram.
And there’s various other diseases that
are best detected by a CT scan where the chest
x-ray is either insensitive or does not give
accurate enough information to tell you exactly
what’s going on, such as bronchiectasis
or the presence of emphysema. And then if
you’re looking for small lesions that might
be causing haemoptysis, or mediastinal abnormalities
which are mainly hidden here in the chest
x-ray and are difficult to see, then the CT
scan is very helpful.
So just to give an example, this is somebody
who’s had a bone-marrow transplantation,
they’ve got a fever and the x-ray doesn’t
really show much. But if you look at the top
of the left lung, there’s a little bit of
shadowing there compared to the right lung.
Now, if you do a CT scan, it actually becomes
very obvious that what’s happening there
is there is a 3-4 cm mass at the top of the
left lung. And this has the characteristics
suggestive of a fungal infection. And that
allows you to treat this patient without any
further investigation if you wanted to. It
just shows the added value you get from a
three-dimensional additional image compared
to just the plain chest x-ray. This green
line indicates the level of the scan.
So there are other x-ray modalities that we
use in lung disease. Ultrasound for example
is very useful in assessing pleural disease
– and I’m not going to discuss that any
more. That’s a picture of an ultrasound
showing a pleural effusion where you can clearly
see the fluid lying between the chest wall
and the lung.
Pulmonary angiogram: that’s a method where
you inject contrast directly into the pulmonary
arteries to visualise them in detail. This
is somebody who has actually clogged off their
left pulmonary artery with an embolus. And
you can see the contrast going through the
arteries on the right-hand side but actually
very little contrast is visible on the left-hand
And the MRI scan actually is not terribly
useful for lung disease but is useful for
the areas around the lung: the chest wall
and the vertebrae. And this is an MRI scan
showing somebody with spinal tuberculosis
and you can see destruction of the
vertebra present where the arrows are indicating.
We also use radionucleotide scan. This is
where you inject a radionucleotide tracer
and that will go to specific types of tissue.
So, for example, there’s a tracer which
we use for bone scans to identify whether
there are any lesions in the bone. And there’s
a ventilation [Inaudible 0:32:56] use for
ventilation/perfusion scans. This is one of
the older methods for identifying pulmonary
emboli that is used less and less nowadays
where you inhale a radioactive tracer and
inject a radioactive tracer and you match
where the distribution is of those two. And
a PE will show up when somebody has an area
which is ventilated but not perfused.
And actually the most important of the radionucleotide
scans nowadays is what we call a PET scan
using radio-labelled glucose. Now that’s
very important because that goes to areas
of active cell metabolism. So it goes where
there’s malignancies and it goes where there’s
an infection and it’s a very useful test
for investigating patients with lung cancer
to assess where the cancer may be – may
have spread to. So it’s a staging test for
lung cancer. And we use it in other circumstances
when monitoring patients with some types of
infections and active inflammatory lung diseases.
So the final resort normally with every type
of investigation is to try and obtain a histological
sample. And actually for the majority of lung
diseases that’s not necessary. However,
for some lung diseases it’s vital. So, for
example, a suspected cancer is absolutely
essential to get histological confirmation.
The same is true for somebody with chronic
sarcoidosis and the same is true for patients
with some types of infection and other lung
And there are actually many different methods
for obtaining lung tissue by biopsy. The commonest
are CT- or ultrasound-guided biopsies of the
pleura, CT-guided biopsies of the lung, bronchoscopic
biopsies that we’ve discussed already, which
can be endobronchial, transbronchial or the
endobronchial ultrasound biopsies of the lymph
nodes. And then, in the last resort, you can
do surgical biopsies and this could be of
the mediastinal nodes or they could be of
the lung tissue. And those are normally done
by video-assisted thoracoscopic surgical techniques
but they do require a general anaesthetic,
an operation and probably being in hospital
for 3 to 4 days, which is quite a heavy problem
for somebody who’s having a diagnostic test
as supposed to a surgery for a curative reason.