Case of the week #10

CHF exacerbation with pleural effusions masking a right complex pleural effusion

with gram positive bacteremia

In this patient, the initial correct diagnosis was a congestive heart failure (CHF) exacerbation and was treated appropriately with IV diuretics. However her symptoms did not improve as much as expected and she was found to have gram positive bacteremia. 

 

When searching for a source, it is important to do a thorough physical exam, looking for cellulitis or abscess, listening for loud murmurs / janeway lesions that could indicate endocarditis, and repeating blood cultures to make sure it is not a skin flora contaminant.

This patient does have a systolic murmur but of course this is very nonspecific. Janeway lesions or splinter hemorrhages are not specific or sensitive, but are an important physical exam finding to look for as they can be present in 20-50% of patients with infective endocarditis.

In this patient, the source may not have been discovered had it not been for pocus.

Visually inspect the mitral and aortic valves in parasternal long axis view to screen for any obvious vegetations present.

Descending aorta

Can see anechoic fluid below the descending aorta which is consistent with a pleural effusion

In the cardiac images, there is no gross abnormality or vegetation hanging off that can be seen with a basic pocus exam (other cardiac views not shown). This does not exclude endocarditis however. Even a formal trans-thoracic echo is only about 70% sensitive for endocarditis.

The left pleural effusion has a anechoic appearance. There is no floating debris or septations within the fluid. We can also see the atelectatic lung floating in the fluid (jellyfish sign). For more on pleural effusions go here.

However when imaging the right pleural effusion, we discover multiple fibrinous septations. This appearance alone should alert you to a possible empyema or exudative effusion. 

There are multiple septations within the hyopoechoic fluid with some mobile debris. This could be an acute or chronic finding but in this clinical scenario, it is very likely a source for bacteremia.

Inferior diaphragm border with 'spine sign' present behind it. 

Can you diagnose type of effusion with ultrasound alone?

Interestingly, there are multiple studies evaluating if sonographic appearance alone is enough to diagnose transudative vs exudative effusions.

 

A 1981 study looked at pleural effusions in 50 ICU patients. They categorized the fluid appearance as: anechoic, complex septated, complex nonseptated, and homogenous echogenic.They noted that the “complex septated loculations had a 74% probability of producing exudative fluid,” while the anechoic effusions were less predictive and divided equally between transudative and exudative. This was in the early days of thoracic ultrasound, and they conclude that a “sonographic negative exam for fluid was helpful in avoiding thoracentesis.” Something we take for granted in 2020.

 

In Taiwan in 1992, pleural effusions in 320 patients were assessed sonographically. 224 were exudate, 96 transudate. Two sonographers evaluated each image which was then compared to the pleural fluid findings. The pleural effusions were classified by the sonographer the same as above:
 

  • Anechoic: echo-free spaces were present between visceral and parietal pleura

  • Complex non-septated: heterogeneous echogenic material was inside the anechoic pleural effusions

  • Complex septated: fibrin strands or septa were floating inside the anechoic pleural effusions

  • Homogeneously echogenic: if homogeneously echogenic spaces were present between visceral and parietal pleura

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They summarized the data as:

  • All effusions that were transudative were anechoic
     

  • All effusions that were septated, complex nonseptated or homogenously echogenic were exudative
     

  • The anechoic effusions were made up of both transudative and exudative effusions
     

  • None of the patterns were specific for malignant effusions

Another study in 2004 of 127 transudative effusions confirmed the heterogenous nature of transudative effusions. Here is how the causes broke down:

They summarized the data as:

  • Anechoic pattern in 45%
     

  • Complex non-septated pattern in 55%
     

  • There was no relationship between sonographic patterns and underlying diagnosis, LDH, protein, white blood count or red blood count

Clinical application

With these studies under our belt, we can only really say two things with confidence:

  • Anechoic pleural effusions can be transudative or exudative about equally

  • Pleural effusions with septations or homogenously echogenic are probably exudative

Complex effusions without septations are less clear cut: likely exudative but can also be seen in transudative effusions.

In this patient, her initial blood cultures grew Streptococcus mitis and her repeat blood cultures were negative. Pulmonology and infectious disease teams were following. A remote CT was discovered which noted some septations a year prior, making a thoracentesis more difficult as the septations were likely thick and difficult to remove without surgery. Given her age and co-morbidities, the decision was made to treat with IV antibiotics only, and the patient did well.

POCUS Med Ed

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