Category Archives: education

Lung ultrasound goes viral for flu season

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Zlines 300x290 Lung ultrasound goes viral for flu seasonMore lung ultrasound tips and examples from Drs. Jim Tsung and Brittany Pardue Jones!

Bacterial pneumonia will manifest as lung consolidation with air bronchograms. The A-line pattern of normal lung will begin to be replaced by B-lines in the area of affected lung:

Here we’ve highlighted the consolidation from the above video as well:

large PNA piclabel Lung ultrasound goes viral for flu season

In contrast, subpleural consolidations and confluent B-lines are more suggestive of viral pneumonia.
So what do these look like?

Subpleural consolidation:

and another example:

Confluent B-Lines:

occur when multiple B-lines coalesce. In contrast, the next example demonstrates multiple discrete B-lines.

Multiple B-Lines:

And now for something completely different

Z-Lines:  Comet tails that arise from the pleural line but DO NOT make it to the bottom of the ultrasound screen. These are not B-lines. These artifacts have not been associated with any pathology, and they do not obliterate A-lines.

For more details on the sonographic appearance of viral lung pathology, check out this article by Jim Tsung.

Hepatization versus Pseudo-Hepatization

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Counter-intuitively, when insonating the lungs of healthy patients, we don’t “see” lung tissue. Instead we see and interpret artifacts arising from the pleural lines and the diaphragm.  These artifacts change with pulmonary disease processes.  In pneumonia, the airway spaces become inspissated with bacterial byproducts and consequently the sonographic appearance of lung tissue changes.

The transformation of lung tissue is termed hepatization: the lung tissue now appears similar to liver tissue.

This can be confusing in the lower lung fields, especially adjacent to the diaphragm because we use the mirror image artifact of the liver and spleen to indicate that lung tissue is normal. This mirrored, artifactual splenic or liver appearance could then be called pseudo-hepatization.

 

 

So, how do we differentiate hepatized lung versus pseudo-hepatized lung?

  1. Never use a single image for your diagnosis, scan through area and convince yourself (then save a representative image or clip for QA).
  2. Be systematic and scan down from the lung apices to the diaphragm.
  3. Hunt for the diaphragm and use it as a dividing line between the lung and the abdominal organs.
  4. Hepatized lung will often have a rim of fluid around it.

Image 1: Normal lung with visible diaphragm

Ultrasound of lung and spleen from Sinai EM Ultrasound on Vimeo.

Image 2: Normal lung with obscured diaphragm

Lung and Spleen Interface on ultrasound from Sinai EM Ultrasound on Vimeo.

Image 3: Hepatized lung at the lower lung field

What the Heck 3

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The Shadow Knows What the Heck 3So we are scanning the left thorax in a patient with shortness of breath, in an effort to assess for pleural effusion. The following video was obtained:

The operator correctly noted the presence of a pleural effusion, and a bit of lung tissue can be seen towards the left side of the screen floating in fluid. In addition, there are THREE shadows evident, each from a different source. Can you spot them?

large LUQ pic What the Heck 3

So let’s take these one at a time, with labels:

large LUQ piclabels What the Heck 3

Shadow A

Is the easiest one. It extends almost from the first pixel at the top of the screen down to the far field. We can’t even see the characteristic echotexture of skin or subcutaneous tissue in the near field. There’s no contact here between the transducer and skin, possibly due to:

  • the probe not touching at all
  • clothing or an EKG lead getting in the way
  • not enough gel (the novice’s answer to everything but sometimes still true)

Shadow B

The most interesting one of the bunch. Probably two major factors at work here. First, this section of diaphragm is a particularly bright reflector so it can create a shadow behind it due to the sheer amount of reflection occurring. Second, the density difference between the diaphragm and pleural effusion is creating a refraction artifact, often referred to as an edge artifact. Beams of sound which were roughly parallel as they struck this interface get bent at different angles based on whether they hit the dense diaphragm or the less dense fluid. The space in between the formerly tightly spaced beams is displayed as blackness, or the absence of returning echoes.

Shadow C

That’s a rib shadow. Did you know that ribs grow back if you remove them?

 

Back to the Source

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Screen Shot 2012 12 29 at 5.06.37 PM Back to the Source

With the proliferation of online educational modalities (blogs, educational websites, podcasts, twitter feeds) designed for rapid dissemination and translation of our basic Ultrasound knowledge to the bedsides around the globe, we must occasionally go back to the source – The Scientific Journal.

Listed below are several ultrasound-specific journals.

What is your favorite source for point of care ultrasound literature goodness?

AAMC article

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logo aamc.gif data AAMC articleThe Association of American Medical Colleges (AAMC) has written an article about ultrasound education at the medical school level. In the current edition of their widely distributed publication The Reporter, they describe programs at the University of South Carolina School of Medicine, University of California (Irvine) School of Medicine, and the Mount Sinai School of Medicine.

The article notes,

With rapid advancements in ultrasound technology, such scenarios as this are becoming more commonplace, as a handful of the nation’s medical schools make ultrasound training a standard part of the curriculum. And there is a push to encourage more schools to use ultrasound.

The full article is available here.

Lung Ultrasound Pitfalls

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US lung consolidation Tsung 500x514 Lung Ultrasound PitfallsThoracic sonography is one of the most rapidly growing areas of emergency and critical care ultrasound. One very important emerging indication is to assess for lung consolidation. The characteristic appearance of consolidated lung is very sensitive and specific for pneumonia, but novices should heed some important pitfalls in making the diagnosis.

Special thanks to Jim Tsung, MD, MPH and Brittany Jones, MD for their tips, videos, and ongoing research in this important field! For further reading on this topic, please see this article.

Pitfall #1 – confusing thymus for a consolidation

Normal thymus in sagittal view:

Thymus (top half of screen) and heart (bottom right). Don’t confuse thymus for lung consolidation. Note there are no air bronchograms, but thymus has a faint speckled appearance.

Normal thymus in transverse view:

Thymus (top half of screen) and heart (bottom right). Don’t confuse thymus for lung consolidation. Note there are no air bronchograms, but thymus has a faint speckled appearance
Pneumonia adjacent to Thymus in transverse view:

Lung consolidation with air bronchograms (top left) adjacent to normal thymus (speckled appearance on top right) with heart (bottom right)

Pitfall #2 – mistaking spleen for consolidation.

This is an important pitfall for everyone to know about. The same issue applies to the liver & stomach. The sensitivity of lung US for pneumonia rises >90% if this mistake is avoided.

Left lower chest- sagittal view:

Be careful scanning the left lower chest (left anterior and left axillary line) – air in stomach and spleen may look like pneumonia if you don’t realize that you have scanned inferior to the diaphragm and past the end of the pleural line. Most common error by novices.

Left lower chest- transverse view:

Be careful scanning the left lower chest (left anterior and left axillary line) – air in stomach and spleen may look like pneumonia if you don’t realize that you have scanned inferior to the diaphragm and past the end of the pleural line.

Pitfall #3- missing pleural effusion

Here are a few examples to refresh your memory.

Left pleural effusion:

Identify:

  • Pleural effusion (anechoic wedge just beneath ribs and pleura)
  • Lung
  • Diaphragm
  • Spleen
  • Air in stomach

Do not confuse spleen and air in stomach for pneumonia.

Right pleural effusion:

Identify:

  • Pleural effusion
  • Lung
  • Diaphragm
  • Liver

Papilledema and the Crescent Sign

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What’s abnormal in this image?

 

Screen shot 2012 08 09 at 6.27.44 PM1 230x300 Papilledema and the Crescent Sign

Here’s a hint.  Here is an example of normal.

 

Screen shot 2012 08 09 at 6.18.41 PM1 256x300 Papilledema and the Crescent Sign

When evaluating for possible elevation in intracranial pressure, it has been shown that optic nerve sheath diameter (ONSD) measurements correlate with elevated intracranial pressures.(1,2)  The optic nerve attaches to the globe posteriorly and is wrapped in a sheath that contains cerebral spinal fluid.  The optic nerve sheath is contiguous with the dura mater and has a trabeculated arachnoid space through which cerebrospinal fluid slowly percolates.

Eye Sono 261x300 Papilledema and the Crescent Sign

ONSD Normal Ranges

Normal Adults < 5 mm
Children >1 yr < 4.5 mm
Infants < 1 yr <4 mm

 

The ONSD is measured 3 mm posterior to the globe for both eyes.  A position of 3 mm behind the globe is recommended because the ultrasound contrast is greatest.  It is best to average two measurements of each eye.  An average ONSD greater than 5 mm is considered abnormal and elevated intracranial pressure should be suspected.

 

ONSD large Papilledema and the Crescent Sign

ONSD Measurement

 

Crescent Sign

In severe cases of elevated ICP, one can see an echolucent circle within the optic nerve sheath separating the sheath from the nerve due to increased subarachnoid fluid surrounding the optic nerve.  Ophthalmologists refer to this as the crescent sign.

 crescent 2 Papilledema and the Crescent Sign

 

 The Case

40 yo female patient presents with several months of frontal headache associated with photophobia and blurry vision.  Symptoms have gotten much worse over the last few days and she has had difficulty reading and watching TV because of her visual symptoms.  She denies fevers, chills, nausea, vomiting, or focal weakness.   Pt is hypertensive 170/100.  Her vital signs are otherwise normal.

  • Visual acuity - 20/30 OD, 20/70 OS
  • CT head is normal
  • Bedside point of care ultrasound

papilledema cropped from Sinai EM Ultrasound on Vimeo.

Papilledema 2 cropped from Sinai EM Ultrasound on Vimeo.

This patient had enlarged ONSD (measurements were 6 mm bilaterally) as well as papilledema(arrow).

 

Papilledema arrow Papilledema and the Crescent Sign

Arrow notes papilledema

 

Lumbar puncture was performed.  Opening pressure was 44.  30 cc’s of CSF was drained and the closing pressure was 11.  The patient’s headache and visual symptoms improved .  She was started on acetazolamide and admitted to the neurology service.  MRI brain prior to lumbar puncture showed posterior scleral flattening bilaterally with protrusion of the optic nerve in the the globes bilaterally consistent with increased ICP.

This patient’s papilledema and increased ONSD correlated with a markedly increased opening pressure during lumbar puncture and suggests that ocular ultrasound may play a role in the ED management of patients with suspected pseudotumor cerebri.

Pseudotumor cerebri

Elevated intracranial pressure in the abscence of intracranial mass lesion.  Most common in young, over weight women. If the diagnosis is missed, persistently elevated intracranial pressure can lead to optic atrophy and blindness.

Treatment

  • Lumbar puncture to drain CSF to a normal opening pressure.
  • Medical:  Diomox (acetazolamide), high dose steroids
  • Surgical : Optic nerve sheath fenestration, VP shunt

Summary

The ability to diagnose papilledema using bedside sonography is useful to emergency physicians, as many non-ophthalmologist clinicians do not feel confident in their ability to perform an accurate nondilated fundoscopic examination. (3)  Ultrasound provides a useful alternative means of determining the presence or absence of papilledema in a patient in whom fundoscopy cannot be adequately performed.

 

 

[1] Geeraerts T, Launey Y, Martin L, et al. Ultrasonography of the optic nerve sheath may be useful for detecting raised intracranial pressure after severe brain injury. Intensive Care Med 2007;33(10):1704-11 [electronic publication 2007 Aug 1]. PMID: 17668184

 

[2] Kimberly HH, Shah S, Marill K, Noble V. Correlation of optic nerve sheath diameter with direct measurement of intracranial pressure. Acad Emerg Med 2008;15(2):201-4. PMID: 18275454

 

[3] Wu EH, Fagan MJ, Reinert SE, Diaz JA. Self-confidence in and perceived utility of the physical examination: a comparison of medical students, residents, and faculty internists. J Gen Intern Med 2007;22 (12):1725-30 [electronic publication 2007 Oct 6].  PMID: 17922165