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

ARDS

Acute respiratory distress syndrome (ARDS) 

acute inflammatory lung injury that causes non-cardiogenic pulmonary edema by increasing alveolar capillary permeability. 

The thickened diffusion barrier leads to hypoxemia via:

decreased lung compliance

inefficient gas exchange

Pulmonary hypertension

increased physiological dead space

Predisposing factors:

Direct lung injury: pneumonia, gastric aspiration, pulmonary contusion, near drowning, inhalation injury, transfusion-related acute lung injury

Indirect lung injury: sepsis, shock, acute pancreatitis, burns, crush injury, fat embolism, and massive transfusion

Diagnosis criteria for ARDS – Berlin definition (all 4 components must be present):

1. Acute onset (1 week or less)

2. Hypoxemia (PF ratio* < 200 mmHg with a minimum of 5 cmH2O PEEP (or CPAP))

3. Pulmonary edema (bilateral opacities on CXR)

4. Non-cardiogenic (not caused by cardiac failure)

*PF (PaO2/FiO2) ratio is the ratio of arterial oxygen partial pressure to fractional inspired oxygen. PaO2 value can be obtained from ABG, and FiO2 is 0.21 at sea level (room air) or depends on supplemental O2.

ARDS is a diagnosis of exclusion so consider first: 

Cardiogenic pulmonary edema, severe multilobar pneumonia, acute exacerbation of pulmonary fibrosis, diffuse alveolar hemorrhage, idiopathic acute eosinophilic pneumonia, dissemination of lymphoma/leukemia, and several others. 

Workup:

Labs: CBC, BMP, LFTs, Coags, VBG followed by ABG, troponin, BNP, lipase, consider DD

Imaging: CXR, POCUS US ECHO and CHEST and consider CT

ED Management:

Supplemental O2

Treat the underlying condition (pneumonia, sepsis, etc.)

Tempered diuresis – non-cardiogenic pulmonary edema takes much longer to respond to treatment than cardiogenic CHF, so avoid being overly aggressive with diuresis, as this may worsen underlying shock and increase likelihood of multi-organ failure

Glucocorticoids — consider steroids when ARDS precipitated by a steroid-responsive process (eg, acute eosinophilic pneumonia)

Be cautious when using non-invasive positive pressure ventilation – the benefit of NIPPV in the initial management of ARDS remains controversial. 

Mostlikely patient will end up being intubated, for vent management suggested strategies are:

Use low tidal volume (6-8 mL/kg) to avoid barotrauma (ideal body weight should be calculated)

And careful FiO2:PEEP ratio titration:

ARDS severity (mortality) predictor 

Mild ARDS – The PaO2/FiO2 is >200 mmHg, but ≤300 mmHg, on ventilator settings that include positive end-expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) ≥5 cm H2O

Moderate ARDS – The PaO2/FiO2 is >100 mmHg, but ≤200 mmHg, on ventilator settings that include PEEP ≥5 cm H2O

Severe ARDS – The PaO2/FiO2 is ≤100 mmHg on ventilator settings that include PEEP ≥5 cm H2O.