Ultrasound - Sub Pleural Consolidation and PE
Case Study
TITLE - PULMONARY EMBOLISM: THE ROLE OF COLOUR FLOW DOPPLER
HISTORY
A woman presents to ED with shortness of breath and pleuritic chest pain following a recent flight.
ULTRASOUND FINDINGS
Using B-mode imaging, there is an area of subpleural consolidation seen in the lung. Colour Flow Doppler demonstrates reduced blood flow in this area, consistent with infarcted lung due to pulmonary embolus. Subsequent CTPA confirmed the diagnosis.
DISCUSSION
Consolidated lung abutting the pleura allows for visualisation of lung tissue, due to fluid in the alveoli transmitting sound waves. Its ultrasound appearance is heterogeneous and hypoechoic, and may mimic the ultrasound appearance of liver tissue (and is often referred to as ‘hepatization’ for this reason). Pulmonary infarction from embolism is one of the possible causes of this appearance. In this case, colour Doppler demonstrates reduced blood flow in the area of consolidation, consistent with PE. Note that the US does not distinguish infective and infarct causes of consolidation but your clinical assessment will do this or at least help.
It is important to reduce the scale (or ‘pulse repetition frequency’, PRF) as low as possible, and increase the colour gain, in order not to miss blood flow.
Note also the colour ‘flash’ artefact seen on the left of the infarcted area, which should not be confused with blood flow. If in doubt, pulse wave (spectral) Doppler should be used to interrogate the wave form and confirm flow.
Prepared by Ahilan Parameswaran and Justin Bowra, SAH
Images
Consolidation – PLAPS Point, ‘Shred’ Sign
Consolidation – Left Lower Lobe Hepatisation
