VOTW: Hepatization of Lung

Here is this week's VOTW:

A 69-year old male with a history of COPD presented to the ED for 1 month of cough and 1 week of hemoptysis. A chest x-ray showed a left lower lobe consolidation vs atelectasis vs effusion. A POCUS was performed to better characterize the area which showed…

Clip 1 and Clip 2 shows "hepatized lung", a large isoechoic area of lung tissue just under the pleura that has a similar echogenecity to the liver which is suggestive of a consolidation. The echogenic jagged line in the far field is the interface between consolidated and aerated lung. Within the consolidation, air bronchograms (scattered echogenic dots and lines) can be seen. 

Findings of pneumonia on lung ultrasound

Hepatization of the lung - Normal lung tissue is not visible on ultrasound as it is filled with air. As pneumonia develops, inflammatory material (fluid, pus) fill the alveoli of the lung, and the affected lung tissue becomes more solid and visible on ultrasound. A large consolidation takes on the appearance of a solid organ like liver and is referred to as “hepatization of the lung”. Atelectasis can also have this appearance.

B-lines are not specific to pulmonary edema and can be see with pneumonia due to the fluid within the alveoli. This may be the only finding in early pneumonia. Focal B-lines are more suggestive of infectious process while diffuse B-lines are more suggestive of pulmonary edema.

Shred sign refers to small hypoechoic lesions abutting the pleura which gives the appearance of a jagged pleural line. This is highly specific for a small subpleural consolidation. The jagged line is the interface between consolidated and aerated lung and not actually the pleural interface.

Air bronchograms (image below) are small pockets of air that are present within the small bronchi within the consolidation seen in both atelectasis and consolidation. Dynamic air bronchograms move in and out along the bronchi with each breath and is more specific for a true consolidation. Static air bronchograms are more suggestive of atelectasis as with complete collapse of the lung air won’t move in or out but can also be seen with consolidation.

Image 1. Air bronchograms

Pleural effusions frequently accompany a pneumonia. Echogenic debris or septations within the effusion can suggest an empyema.

Tips and tricks on Lung Ultrasound

• Use the curvilinear probe using the Lung settings

• Orient your probe with the probe marker towards the head, find two ribs which are hyperechoic with posterior shadowing and identify the shiny shimmering pleura in between

• If looking for B-lines, increase the depth so you can see the b-lines which extend all the way down the screen. This lets you differentiate B-lines from comet tail artifacts which do not extend all the way down the screen and are not pathologic.

• If looking for a pneumothorax, decrease the depth so you can focus at the pleura and more easily look for lung sliding. You can also switch to a linear probe for higher resolution

• When looking for a pleural effusion at the lung bases, bring the vertebral bodies in view so that you can look for a “spine sign” (extension of the spine above the diaphragm which would indicate the presence of a pleural effusion)

Case conclusion

A CTA Chest showed a dense left lower lobe consolidation. The patient was given IV antibiotics and admitted for the management of pneumonia and hemoptysis.

Here is a great review of lung ultrasound for pneumonia: https://litfl.com/lung-ultrasound-pneumonia/

Happy Scanning,

Your Sono Team

VOTW: Necrotizing Fasciitis

This week’s VOTW is brought to you by Dr. Aaron Ryoo!!

17 yom presented to the Bay Ridge (Free-standing) ED with 5 days of right lower extremity pain that started as a scab. Two days later he had an I&D of his right calf by his PMD. Over the day prior to presentation, the patient became febrile with worsening pain and erythema. On exam, he had a large erythematous indurated region along his calf with pain out of proportion to exam and purulent/bloody drainage from the previous I&D site. A POCUS was performed which showed…

Clip 1 shows a soft tissue image of the calf area, with cobblestoning of the subcutaneous tissues consistent w/ cellulitis. Deep to the subcutaneous tissue there is edema along the muscle/fascial layers and several hyperechoic foci of air with “dirty shadowing” concerning for necrotizing soft tissue infection (NSTI) by gas-forming bacteria.

Necrotizing soft tissue infection

POCUS is a quick and easy way to evaluate for the presence of soft tissue gas when there is a concern for NSTI. Other findings include fluid collections along the fascial plane and findings of overlying cellulitis. Overall, POCUS has a sensitivity of 85-100% and specificity of 44-98% for NSTI1. Fluid accumalation along the fascial planes is most sensitive finding while subcutaneous emphysema is most specific (100%) based on a recent meta-analysis1

You can use the acronym "STAFF" to remember the findings:

ST = subcutaneous thickening

A = air or emphysema

FF = fascial fluid layer greater than 2mm

An I&D can also introduce air into the area but in a septic patient this should be assumed to be necrotizing fasciitis until proven otherwise.

Image 1. Dirty shadowing is caused by sound wave-reflecting objects like gas (think of shadowing from bowel gas). The shadow created is not unformily anechoic. Clean shadowing is caused by sound wave-absorbing objects (think gallstones and bones). The shadow created is unformily anechoic. 

Image 1. Dirty shadowing

Findings of cellulitis on POCUS

• Skin and subcutaneous tissue appears thickened and diffusely hyperechoic

• Area becomes “hazy” with loss of clear borders between epidermis, dermis and hypodermis (subcutaneous tissue)

• Cobblestoning- hyperechoic fat lobules in the subcutaneous tissue become separated by edema giving the appearance of cobble stones

Back to the patient:

CT imaging showed “deep perifascial bubbles of gas and edema along the lateral head of the gastrocnemius". Patient was transferred emergently to Maimo and was taken to the OR by general surgery the next morning for an I&D. Purulent material was found along the fascial planes confirming the diagnosis of necrotizing fasciitis.

References:

Marks et al. Ultrasound for the diagnosis of necrotizing fasciitis: A systematic review of the literature, The American Journal of Emergency Medicine, Volume 65, 2023, Pages 31-35

Happy Shadowing,

Your Sono Team

VOTW: Lung Point

Hi all, this week's VOTW is presented by Drs Forrest, Yang and Schiller!

A 71 year old male w/ hx of COPD presented to the ED for altered mental status. He was found to be obtunded due to hypercapnia and was intubated in the ED. Several hours after admission to the MICU the patient suddenly desaturated to 64%. 

A POCUS was rapidly performed which showed…

Clip 1 shows a POCUS of the R anterior chest. On the left side of the screen, the pleural line has absent lung sliding. From the right of the screen, normal pleura with lung sliding is seen coming into the image with every breath. This is a “lung point” which is the exact point at which the pneumothorax starts. A chest x-ray confirmed a large R sided pneumothorax with mediastinal shift. A chest tube was placed by the ED team for a tension pneumothorax with improvement in vitals.

Image 1 shows an M-mode image obtained expertly by the team at the lung point which shows both "seashore sign" indicative of normal lung as well as "barcode sign" indicative of pneumothorax in one clip. You'll see this only if you use M-mode at the lung point.

M-mode showing areas of “sandy beach” alternating with “barcode sign” at the lung point

Lung sliding

In normal lung, the pleural line will appear to shimmer due to the movement of the visceral and parietal pleura sliding against each other. With a pneumothorax the contact between the two pleura are lost and the pleural line will appear still. 

*The presence of lung sliding rules out a pneumothorax at the location of the chest you are scanning. 

*Image the least dependent site (where air is most likely accumalate) to maximize sensitivity of the test (anterior chest in a supine patient).

*Reduce your image depth all the way! This way you don't have to squint while looking for lung sliding

Lung point

This is the point at which normal lung sliding and absent lung sliding are seen next to eachother simultaneosuly and is the exact point where the viseral pleural is peeling away from the parietal pleura. If found, this finding is highly specific for pneumothorax. It won't be seen with a large pneumothorax that envelops the entire lung.

Does absence of lung sliding always indicate pneumothorax?

No. Absence of lung sliding can be seen with many conditions including a bleb from COPD, right mainstem intubation (no left-sided lung sliding), patients w/ previous thoracic surgery (such as pleurodesis or VATS), pleural adhesions, ARDS, pulmonary fibrosis, atelectasis, and phrenic nerve paralysis. If the patient is stable, confirm the diagnosis with a chest x-ray or CT prior to placing a chest tube.

Which lung ultrasound artifacts rule out pneumothorax?

A-lines are reverberation artifacts that can be generated by air in normal lung tissue or air in the pleura so cannot be used to rule out pneumothorax.

B-lines indicate the presence of interstitial edema which can only be seen if the lung tissue is abutting the pleura. Even seeing one B-line is enough to rule out pneumothorax.
Happy sliding,

Your Sono Team