Case Of the Week #6
Neutropenic fever due to left lower lobe pneumonia
In this patient who presented with fevers and chills after starting chemotherapy, searching for a source of infection is of course the first step. With a dry cough, pneumonia should be first on the differential. She is especially susceptible to various pneumonias - viral, bacterial or fungal - given her neutropenia.
Chest x-rays can be very useful if they detect an infiltrate, but many times they are indeterminate and a closer look at both lungs is warranted.
Using standard lung ultrasound, starting from top of the lung to bottom and sliding one rib space at a time, you can get a very thorough in-depth look at the lung in all lung spaces.
Using Dr Lichenstein's work as a guide, you can start by evaluating the lung in 3 general areas.
Great for quick evaluation of pneumothorax and 'interstitial syndrome'
Evidence of large pleural effusions or large consolidations
Contains the "PLAPS" point (posterolateral alveolar and/or pleural syndrome) , which has 90% of consolidations
In order to qualify as a consolidation it must meet the following 6 criteria:
1. Pattern located at the thoracic level
Since true lung consolidation can mimic the appearance of abdominal organs, it is important to delineate your thoracic borders.
2. Pattern arising from the pleural line
Most consolidations reach pleural line, making them accessible to ultrasound imaging.
3 Real image, i.e. not artifactual
An A line is an ultrasound imaging artifact that can be visualized on ultrasound but is not actually present in the body, whereas a consolidation is a real image.
4. Tissue-like pattern reminiscent of the liver
Also known as “hepatization”
5. Anatomic boundaries, with superficial boundary at the level of the pleural line or the deep boundary of a pleural effusion if present, and a deep boundary usually irregular with the aerated lung
6. Absence of the “sinusoid sign”
With true lung consolidation, the size of the consolidation does not vary with inspiration, compared to a pleural effusion which does vary.
As you scan down the left lung, we can see predominantly A-line pattern until you reach the left lower lobe. Here you can see some focal B-lines and a disrupted pleural line.
Moving down one rib space we can now see the consolidation. It is hypoechoic, irregularly shaped structure with hyperechoic spots (air bronchograms).
Instead of strictly ultrasound artifact seen below the pleural line, we see a hypoechoic structure, with morphology consistent with a liver, hence the term 'hepatization.' Note the jagged borders of the consolidation consistent with a "shred sign."
Pleural line, zoomed in
Zooming into the pleural line, you can clearly see a disruption of the normal pleural line. On either side of the hypoechoic consolidation you can see B-lines projecting from the pleural line consistent with focal edema/inflammation related to the pneumonia.
In the 2004 study by Dr Lichenstein et al of consolidations found on ICU patients, of the 65 consolidations seen on chest CT, 59 of them were detected with ultrasound and 6 were missed. In the 52 controls without CT evidence of consolidation, lung ultrasound was negative in 51 and positive in 1.
This remarkable accuracy is much better than a chest x-ray could do, and begs the question of why we don't do lung ultrasound more ofter!?