Ultrasound Pearls

Author:	Reed.Simons
ID:	26256
Filename:	Ultrasound Pearls
Update:	2010-08-30 22:31:38

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Name 2 signs indicative of normal lung on Thoracic US looking for PTX:
<answer>
The two signs seen are lung sliding and comet tails.  Lung sliding refers to the movement of lung along the pleural space.  Comet tails are "ray-like" artifacts created by highly reflective surface layters between the pleural and visceral lung layers. Both of these signs are indicative of a normal lung.

Reference:  Nagdev, A.  Murphy, M. "Ultrasound Detection of Traumatic Anterior Pneumothorax." ACEP News. December 2008 <http://www.acep.org/PrintFriendly.aspx?id=43362> Accessed 2.16.10.</answer>

In general, what are the minimum quantitative beta HCG levels to visualize a gestational sac on transvaginal (TV) and transabdominal (TA) ultrasounds?
<answer>
In general, the accepted minimum beta-HCG levels are 1,500 for transvaginal (TV) and between 4,000-6,500 for transbdominal (TA) probes.  TV probes have a higher frequency and have better resolution.  TA probes use a lower frequency and thus lower resolution.

Reference: Noble, V, et al.  "First Trimester Ultrasound." Manual of Emergency and Critical Care Ultrasound. Cambridge University Press. 2007. pg. 87.

Clinical Bottom Line:  The minimum beta-HCG levels to view a gestational sac in transvaginal and transabdominal views are 1,500 and 5,000, respectively.</answer>

In addition to a pericardial fluid, which ultrasound findings point towards a cardiac tamponade?
In normal physiology, the RV will contract during systole and the RA will contract during diastole.  A pericaridal tamponade can reverse this normal pattern.  Furthermore, the IVC will be not change with variation due to high filling pressures in the heart from external compression.

<question>
An 80 year old male with history of BPH is sent to the ED by the nursing home for a "swollen abdomen" for 1 day.  You use the ultrasound to evaluate for obstruction.  The dimensions of the bladder are below:

Length: 3 cm Width: 5 cm Diameter:  4 cm

What is the approximate volume of urine?
</question>
<answer>
-Bladder volume measurements is equal to width x depth x volume x 0.7 +/- 10%.   
-3cm x 5cm x 4cm = 60cm^3 (or 60mL) 60 mlx  0.7 = 42 ml
-Use this measurement to evaluate the approximate amount of urine in the patient's bladder.  
-If this is greater than 50 cc, use a Foley catheter to drain.

Clinical Bottom Line: Width x depth x length x 0.7 (cm) = bladder volume mL (+/- 10%)

Ref: Dudley, NJ, et al. "Clinical agreement between automated and calculatedultrasound measurements of bladder volume."  The British Journal of Radiology, 76 (2003), 832–834 E 2003 The British Institute of Radiology. http://bjr.birjournals.org/cgi/reprint/76/911/832.pdf</answer>

What is the standard orientation of the pointer for ED ultrasounds?
<answer>
As a general rule, we aim the pointer towards the patients head and to the right.  The indicator on the screen will be on the left of the screen.  By orienting it this way, everything will be lined up.

Clinical Bottom Line:  The probe indicator is always oriented towards patients head and right side.  Accordingly, the left side of your view indicates to patients right and head.</answer>

A 30 year old female presents with headaches for the past 72 hours hours of gradual onset.  She rarely gets headaches and has been seen at another emergency department.  The patient states, "All they did was a CAT scan of my head and sent me home with Vicodin."  On physical exam, all VS are normal with a normal cardiac, pulmonary, & neurological exam.  You decided to evaluate her optic nerve sheath diameter with the ultrasound.  Where should the diameter of the optic nerve sheath be measured?
<answer>
Clinical Bottom Line:  The optic nerve sheath diameter is measured 3 mm behind the globe.  If it is greater than 5 mm, this correlates well with an ICP greater than 20 cm H20.

One study revealed that a optic nerve sheath diameter (ONSD) > 5 mm performed well to detect ICP > 20 cm H2O with a sensitivity of 88% (95% CI = 47% to 99%) and specificity of 93% (95% CI = 78% to 99%).

Kimberly, HH, et al. "Correlation of Optic Nerve Sheath Diameter with Direct Measurement of Intracranial Pressure." Academic Emergency Medicine. Vol. 15, Issue 2. pp. 201-04.  2008.  <http://www3.interscience.wiley.com/journal/119413621/abstract?CRETRY=1&SRETRY=0> Accessed 2.14.10.</answer>

A trauma patient comes in and is intubated by EMS providers.  You listen and hear absent breath sounds on the left side.  Using the ultrasound, you evaluate for pneumothorax. You note absence of comet tails, seashore sign, and lung sliding on the left chest.  The patient has normal vital signs.  What of the following is the next best step?
<answer>
Order a portable chest X-ray, and you will find that the patient has a right main stem intubation.  This results in absence of lung movement on the left lung.  Pleural effusions, absence of ventilation, poor inspiration on one side, may resemble a PTX.  Get the CXR for confirmation of tube placement.

Clinical Bottom LineWatch out for pneumothorax imposters: Absence of ventilation, Poor inspiration, Hemothorax, Pleural effusion, Right main stem inbutation</answer>

Dr. Smith uses ultrasound for placement of central lines.  He visualizes the internal jugular vein and takes a picture. Then using a skin marking pen, he pinpoints the exact location he will penetrate. He sets the probe down and successfully cannulates the vessel using his identified landmark.   His documentation includes medical necessity, interpretation, and images before cannulationHe has satisfied all requirements to bill for a central venous line with ultrasound guidance.  True or False?
False.  This question differentiates between static and dynamic central line insertion, and the need for using real-time visualization during the proceure. In 2004 CPT designated a new code specifically for central venous access with ultrasound guidance (76937). The current CPT description is:“Ultrasound guidance for vascular access requiring ultrasound evaluation of potential access sites, documentation of selected vessel patency,concurrent real-time ultrasound visualization of vascular needle entry, with permanent recording and reporting.“There are several unique aspects of the central venous and peripheral vascular access with ultrasound guidance code of which users must be aware. The first is that the code is intended for use only when the ultrasound is used with the “dynamic” technique, as opposed to the “static” technique which is not considered a reimbursable service.The static technique utilizes the ultrasound to identify the vessel, but is not used during line placement. In the dynamic technique the physician uses the ultrasound throughout the procedure from initial identification of the vessel through direct visualization of the needle entering the vessel. A recorded image of the procedure is required for coding.When coding a central line placement under direct dynamic visualization with ultrasound it is appropriate to code 76937 for vascular ultrasound guidance and 36556 for the adult central venous line placement.access is a single thermal print of the angiocatheter needle in the vessel obtainedwhile the procedure is occurring. A cineloop, foot pedal, DVD recorder, or anassistant is helpful in obtaining this imageAn example of adequate image documentation for vascular access is a single thermal print of the angiocatheter needle in the vessel obtainedwhile the procedure is occurring. A cineloop, foot pedal, DVD recorder, or an assistant is helpful in obtaining this image Reference:1) Ultrasound FAQs. ACEP Practice Resources. http://www3.acep.org/practres.aspx?id=30502 Accessed 1/12/10.2) ULTRASOUND CODING AND REIMBURSEMENT DOCUMENT 2009 EMERGENCY ULTRASOUND SECTION,  AMERICAN COLLEGE OF EMERGENCY PHYSICIANS http://www.acep.org/workarea/downloadasset.aspx?id=33280 Accessed 1/28/10.  Clinical Bottom LineWhen doing ultrasound guided central lines, document indication, what you see, and record an image or video of the needle in the vein.

Pneumothorax imposters:
-Absence of ventilation
-Poor inspiration
-Hemothorax
-Pleural effusion
-Right main stem inbutation

True or False?  By changing the gain on the ultrasound machine, you increase the frequency of ultrasound waves.
<answer>
FALSE: Gain changes the <strong><span style="text-decoration:underline;">amplification</span></strong> of the returning signals, but does nothing to alter the frequency of the ultrasound waves.  Increasing gain may result in more artifacts created on your screen.  Adjust gain to have the right amount of brightness in your images.

Clinical Bottom Line:  Gain amplifies the returning sound waves, but does not change frequency.</answer>

TV probes have a higher frequency and have better resolution.  TA probes use a lower frequency and thus lower resolution.

Clinical Bottom Line: The minimum beta-HCG levels to view a gestational sac in transvaginal and transabdominal views are 1,500 and 5,000, respectively.

Reference: Noble, V, et al.  "First Trimester Ultrasound." Manual of Emergency and Critical Care Ultrasound. Cambridge University Press. 2007. pg. 87.</answer>