Once the anterior and lateral surfaces have been scanned, the patient is asked to sit up and the squares on the posterior surface are scanned using the same principles as described for the anterior and lateral surfaces

Again in each scanning zone it is noted whether pneumothorax, pleural effusion or multiple B-lines are present or whether only normal findings are present

As with other kinds of sonography, FLUS findings cannot stand alone and should be used as an adjunct to clinical assessment and other diagnostic modalities

Presence or absence of the interstitial syndrome is a powerful tool with both a high sensitivity and specificity for ruling in and ruling out pulmonary edema in patients with acute dyspnoea

The interstitial syndrome has many causes why it is less specific in some settings such as a intensive care unit

In ARDS the changes found with LUS are not necessarily gravity dependent

Hence, the number of B-lines are not necessarily most pronounced in the dependent part of the lungs

Furthermore, spared areas with no B-lines are often seen

As in interstitial lung disease, in ARDS the visceral pleura is also often affected, and therefore in areas can appear thickened and fragmented

Not all interstitial lung disease causes interstitial syndrome

In interstitial lung disease the pulmonary changes are not gravity dependent, hence the number of B-lines are not necessarily most pronounced in the dependent part of the lungs

Furthermore, spared areas with no B-lines are often seen

In interstitial lung disease, such as idiopathic pulmonary fibrosis, the visceral pleura is also affected

The visceral pleura therefore in some areas can appear thickened and fragmented which is often not the case in simple pulmonary edema

LUS cannot differentiate between cardiogenic and non-cardiogenic pulmonary edema

Supplementary focused assessed transthoracic echocardiography (FATE) is an ideal tool which can be used to assess whether interstitial syndrome is of cardiogenic origin or not

In both cardiogenic and non-cardiogenic pulmonary edema the grade of increased density of the lungs are most severe on the posterior surface of the lungs compared to the anterior surface (if the patient has been lying down)

The number of B-lines tend to be higher more posteriorly than anteriorly and there are no sparred areas with no B-lines in the dependent regions of the lungs

The visceral pleura are not affected by pulmonary edema and the pleural line therefore appears normal.

The video is of LUS of the right upper anterior quadrant (1R) of a patient with cardiogenic pulmonary edema

As mentioned there are many causes of interstitial syndrome

Often the clinical setting and patient history can help to establish the cause of interstitial syndrome

But some basic ultrasonic findings can also be used as a rough guide to differentiate between the different causes

Based on patient history and primary assessment, a list of some of the most common and important differential diagnoses would be:

– COPD exacerbation
– Heart failure with pulmonary edema
– Pneumonia
– Pulmonary embolism
– Pleural effusion
– Pneumothorax

68 year old female with severe COPD

Admitted with progressive dyspnoea and coughing, symptoms had lasted 14 days, possible fever

Primary assessment:
Auscultation: Prolonged expiration, wheezing. No murmurs. No edema or tenderness of the legs

The following case illustrates how FLUS can be used in an emergency department to rule-in or rule-out cardiogenic pulmonary edema