Tag Archives: Lung

Complex pleural effusion

As we saw before, a simple transudative pleural effusion is anechoic. On the other hand, presence of echogenicities in the effusion is suggestive of complex/exudative pleural effusion. The term ‘plankton sign’ is often used to indicate debris appearing as swirling, punctiform echoes in such effusions and may indicate infection or hemothorax depending on the clinical context. Rarely, it can be seen in simple effusions after aggressive diuretic therapy. As the collection progresses, fibrin is activated and septations or loculations appearing as thin hyperechoic lines begin to form within the fluid collection, resembling a ‘spider web’. This is an important finding because effusions with septae are more likely to require a surgical intervention rather than a chest tube drainage and antibiotics alone.

Following are several examples of complex pleural effusion/empyema.

Not every spine sign is from pleural effusion

We have previously discussed the utility of ‘spine sign’ in diagnosing pleural effusion on POCUS. One of the short videos also talks about this. However, it is important to note that this sign is not specific to effusion. Anything that provides a medium for the ultrasound beam to pass through in the lower chest allowing visualization of vertebral bodies above the diaphragm gives spine sign. For example, lobar consolidation, pulmonary contusion or a mass can do this. Below is an illustrative image shared by Dr. Robert Jones. There is trace pleural effusion, but the spine sign is mainly coming from consolidation in this case.

Not a routine pleural effusion

This is an image obtained from the perisplenic window in a patient with gun shot wound. At first glance, it looks like a regular pleural effusion with atelectatic lung above the spleen. If you take a closer look, a huge mass of jelly-like clotted blood can be seen in between the spleen and collapsed lung surrounded by anechoic fluid, which is most likely unclotted blood (i.e., hemothorax) in this clinical context. Sonographic image courtesy: Dr. Robert Jones.

More relevant scenario for internal medicine folks would be a patient with hypercoagulable state undergoes thoracentesis and follow up chest ultrasound demonstrates this finding. Though this degree of bleeding is uncommon, fibrin stranding is often seen in such cases, which can be confused with pleural effusion of infectious origin. Interpretation of POCUS findings in the right clinical context is the key.

Similar to the above case but a different scenario, here is an interesting image shared by Dr. Hailey Hobbs. What looks like liver initially is actually a well-circumscribed empyema!! Note the heterogeneous echotexture and moving particles in that structure. Take home message: Always slide through the area of interest instead of a ‘single point’ examination.

Visualization of the right pleural effusion from the abdomen

Sometimes, pleural effusion may be noticed incidentally on abdominal scans. Below image shows transverse section of the liver with anechoic area in the posterior aspect, which corresponds to right lung/pleural area; black = fluid = pleural effusion. The bright line encircling the liver separating it from the fluid represents diaphragm.

Note the anatomic correlates – the ultrasound beam is actually oblique in between the two transverse sections shown. In such cases, go up and scan in the coronal plane to confirm your findings.

Below is a nice example showing the right pleural effusion in both transverse and coronal planes. Also note small amount of ascites in between the diaphragm and liver tissue.

The Shred Sign

As we have seen previously, lobar consolidations tend to be well-defined, often accompanied by a small pleural effusion. However, small subpleural consolidations (of course, ultrasound does not detect if they are not subpleural) are separated from the surrounding aerated lung by an irregular margin, like a torn paper called the ‘shred sign’. The brightness is because of the air, which scatters the ultrasound beam. It is also known as the fractal line. Here is an illustrative image.

Another example

Sometimes, the consolidation might appear anechoic mimicking a pleural effusion. But the presence of shred sign as in this example is specific to consolidation.

Lung Mass

Occasionally, you may stumble upon a lung mass while evaluating for B lines or other common pathologies. Particularly, ultrasonography is good at detecting primary and metastatic lung masses adjacent to the pleural surface. They typically appear as hypoechoic areas that are distinct from consolidated or hepatized lung, with normally aerated lung appearing in the scan field with respiration. Consolidation and fluid bronchograms may be been seen adjacent to the mass.

It is interesting to note that ultrasonography has been shown to have better sensitivity and specificity (89% and 95% respectively) for assessing chest wall involvement by a lung tumor compared to CT scan. Extension of the tumor beyond the parietal pleura into the chest wall can be determined if the mass breaches the pleura and stops moving with respiration. If trying to find this, use a high resolution linear probe. Spectral Doppler may be helpful in differentiating malignant versus benign masses but it is beyond the scope of NephroPOCUS.

Lung contusion

While nephrologists are not the first line of contact for trauma patients, we are often asked to evaluate the need for renal replacement therapy in these patients. It is important that we are aware of the sonographic findings seen in lung contusion so that we don’t confuse them with interstitial syndrome. As mentioned before, B-pattern in two or more sonographic lung zones bilaterally is suggestive of interstitial syndrome and this term encompasses pulmonary edema of various causes. Usually the pleural line is regular in these cases unless there is underlying lung disease such as pulmonary fibrosis.

Lung contusion is typically associated with B-lines in conjunction with pleural line irregularities, subpleural hypoechoic areas and may be localized pleural effusion. Unless the trauma is diffuse, these findings are localized to certain lung zones. The B-lines are frequently confluent, which means, too numerous and difficult to identify each line separately. In addition, Z-lines can be seen: lines that arise from the pleural line and fade away vertically and do not reach the edge of the screen.

It is also important to note that the contusion can be associated with pneumothorax, particularly in cases of rib fracture. Presence of B-lines almost always rules out pneumothorax even when you are not sure about absent pleural sliding. It is because there is air in between pleural layers, which does not allow B-lines to form. If you notice absent pleural sliding and suspect pneumothorax, look for ‘lung point’, which is the junction between normally sliding pleura and the pneumothorax with absent sliding. It is virtually diagnostic of pneumothorax.