Pulmonary Oedema
What is Pulmonary Oedema?
• Abnormal accumulation of fluid within
the lung tissue
– The excess fluid may collect in different
parts of the lung according to the severity
of the condition and the cause
Upper lobe pulmonary venous
blood diversion
• This can be an early sign of pulmonary
oedema
• Normally, the upper lobe pulmonary
veins are smaller than the lower lobe
veins
• In elevated left heart pressures, these
upper lobe veins become engorged with
blood
Normal
Upper lobe diversion
Note how the upper lobe
pulmonary veins are so
small, they are hardly
seen
The upper lobe
pulmonary veins are
dilated (upper lobe
diversion)
Sequence of Pulmonary Oedema 1
• The first part of the lung to become
involved is the interstitial space.
– Fluid first builds up in the lymphatic spaces
and in the bronchial walls
– These structures are normally not large enough
to be visible on a CXR, but in pulmonary
oedema, the fluid accumulation is so great that
they can be seen.
At this stage, the normal sharp margin of the central vascular
structures is lost, and thickened bronchial walls can be seen
Abnormal thickened
bronchi – look like polo
mints (“peribronchial
cuffing”)
Vascular contours not as
clearly defined as normal,
due to fluid in lymphatic
tissue (“perihilar haze”)
Sequence of Pulmonary Oedema 2
• As the fluid build-up continues, the
septae between small units of lung
tissue (pulmonary lobules) also become
engorged with fluid.
• This is particularly noticeable in the
lower lateral parts of the lung and small
lines parallel to the chest wall become
visible – Kerley B lines.
Kerley B lines in a patient
with interstitial pulmonary
oedema. Fluid may also
collect in the fissures (not
shown).
Sequence of Pulmonary Oedema 3
• Once the interstitial space becomes
saturated, the fluid then accumulates in
the pleural space (pleural effusions).
• Eventually, fluid gathers within the
alveolar space – alveolar oedema. This
can be in a perihilar (“bat wing”)
distribution or throughout the lungs.
This is “Bat wing”
pulmonary
oedema. There is
perihilar
consolidation with
relative sparing of
the extreme apex
and base
What causes Pulmonary Oedema?
• There are many causes!
• Three important causes include:
– Left heart failure
– Valvular Heart Disease
– Hypoalbuminaemia
Pitfalls in Diagnosing Pulmonary
Oedema on CXR
• Severe alveolar pulmonary oedema can look
identical to adult respiratory distress
syndrome, pulmonary haemorrhage and
extensive pneumonia.
• Interstitial pulmonary oedema can also look
similar to other conditions.
• Upper lobe pulmonary venous blood
diversion alone is not pulmonary oedema – it
just reflects increased left heart pressures.
Always treat the patient – not the chest X-Ray
Take Home Points
• The CXR is a useful tool in confirming
suspected pulmonary oedema
• The pattern of CXR abnormality
depends on the anatomical location of
the oedema
• The CXR is not a substitute for clinical
examination and should be used with
other information (e.g. ECG)