Mount Sinai Emergency Medicine Ultrasound

The subxiphoid four chamber view is commonly used in cardiac assessments and the FAST exam and for many is the initial “go-to” view of the heart. Difficulty obtaining this window can frustrate novice and seasoned operators, and there are a few tips which can help optimize the view.

1. It’s called SUB-xiphoid for a reason. Don’t jam the probe up against the xiphoid process. Imaging through bone is difficult, the patient will be in pain, and the angle is too steep. Instead, place the probe a few centimeters south of the xiphoid process and work up from there.
2. Get a good view of the liver, THEN use that to get a good view of the heart. You may find that starting to the patient’s right of midline gives a better liver window, since the stomach tends to obscure the subxiphoid view as you go further left.

This video illustrates the huge difference that left vs. right can make. It was taken with the probe in a midline subxiphoid position. Starting with the probe angled towards the patient’s left, the entire screen is obscured by gas in the stomach. As the operator changes the angle towards the patient’s right, we see the liver come into view. This yields an excellent window through which the heart can be visualized.

The figure below, taken from the midpoint of the video, illustrates the point a bit more clearly. To the right of the green line (patient left), superficial stomach gas (arrow) obscures everything behind it, creating a terrible view. On the other side of the green line, liver (L) is visualized which creates a good window for viewing the heart behind it.

One common source of confusion or false positives in the FAST exam is the assessment of the left upper quadrant. We’ve already covered some tips on improving your view of the spleen. This post will illustrate how the stomach can mimic free fluid to the unprepared.

The first image shows a perisplenic (left upper quadrant) view on ultrasound. Note the spleen (S), kidney (K), and diaphragm (D).

As the operator fans anterior and posterior to assess for fluid, anechoic fluid with some dirty shadows and slightly irregular margins is seen (bounded by arrows). This structure is often visualized anterior and medial to the spleen, and represents fluid within the stomach.

The video better illustrates fanning through a sagittal plane and encountering this common artifact.

Scan through the area carefully to ensure this fluid is all accounted for within the confines of the stomach, and does not layer out around the kidney, spleen, or highlight bowel loops at its margins.

Finding the right angle is critical to optimal imaging. In fact ‘right angle’ or perpendicular imaging is the best way to get a clear image. At 90 degrees, many more sound beams reflect back to the transducer than at more shallow angles.

In addition, the ultrasound energy is more spread out when it connects to the tissue at an angle, as seen above.
In this image of the kidney, notice the inferior aspect of the kidney (right arrow) is imaged at nearly 90 degrees. The white lines represent the plane of the kidney.

It has the sharpest border and is well-distinguished from the liver. The middle arrow represents the path of ultrasound energy hitting the the kidney off 90 degrees.  Not a bad image but doesn’t look as good as the one imaged at 90 degrees. Finally, the left arrow represents the beam hitting the kidney almost parallel. Note that the kidney-liver interface looks fuzzy and there is a great loss of detail. Most of the ultrasound energy is reflecting off the surface AWAY from the transducer- hardly any is available to reflect back towards the transducer and yield a good image.

Thus, angling the probe 90 degrees to the structure you want to image can increase resolution and improve your image quality.

We’ve all seen ultrasound augment the physical examination and even allow for assessments we could not otherwise accomplish at the bedside. One great example is the use of ultrasound to check the pupillary light reflex. If you are wondering why a pen light would not suffice for this physical examination standby, you have never encountered a patient with facial trauma whose eyes were swollen shut.

We already know what to look for without ultrasound (thanks to Greyson Orlando and Wikipedia for the GIF):

By directing the beam of a high-frequency linear array transducer through the plane of the iris, you can obtain the following image (while shining a light through the closed eyelid of the same or contralateral eye):

It takes a bit of practice to align both planes, and not worth the trouble if the patient can open their eyes.

Placing a Tegaderm over the closed eye prior to applying gel can make cleanup much easier afterwards (a useful tip for any type of ocular ultrasound).

Further reading:

• Sargsyan AE, Hamilton DR, Melton SL, et al. Ultrasonic evaluation of pupillary light reflex. Critical Ultrasound Journal. 2009 1(2): 53-57.
• Harries A, Shah S, Teismann N, Price D, Nagdev A. Ultrasound assessment of extraocular movements and pupillary light reflex in ocular trauma. Am J Emerg Med. 2010 Oct; 28(8):956-9.

Hippocrates, Galen, and a host of classical physicians wrote extensively on the spleen and its maladies. As I’m sure you recall, the spleen is tasked with the metabolism of black bile. Failure of the spleen to clear this fluid leads to melancholia.

Fast forward to now, and we also seek black fluid near the spleen. Using ultrasound.

It can be challenging to visualize the spleen due to the standard obstacles of patient habitus, bowel gas, rib shadows, or suboptimal positioning. If you become frustrated, just think back to your physical examination class where I’m sure you were taught to palpate the spleen tip. How did that work out for you?

Here are a few tips on better visualization of the spleen, useful for the perisplenic view of the FAST exam.

• The spleen is best imaged near the posterior axillary line above the ribs- the operator’s knuckles will brush the stretcher when holding the probe
• When the patient takes a breath in, the spleen moves inferiorly with the diaphragm
• When lung blocks the upper portion of spleen/diaphragm, start inferiorly and angle up through spleen, using the inferior aspect of the spleen as a window to superior aspect
• Instead of a ‘pure’ sagittal probe orientation, try to angle angle the probe obliquely to increase amount of probe between ribs. This will reduce the negative impact of rib shadows in the left upper quadrant view.

Here’s a schematic to illustrate that last point. Not that probe rotation increases the amount of window obtained between the ribs.

In the first ultrasound below, the rib shadows (arrows) obscure the view.

By rotating the probe, the spleen (S) is better visualized.

Like everything else, this requires a bit of practice. Remember, fluid can accumulate anywhere around the spleen and therefore it must be imaged in its entirety. It is NOT sufficient to view the interface between the spleen and right kidney, as if this view was just a mirror image of Morison’s Pouch.