One of the most common pitfalls in gallbladder sonography is confusion with the structure which abuts it in the right upper quadrant – the duodenum. This loop of bowel can easily be mistaken for the gallbladder especially if it contains a mixture of fluid and solid materials. So how can we tell them apart?
- has a bright (echogenic) wall
- is surrounded by liver
- attaches to the middle hepatic ligament
- is a contained structure
- can be traced to the portal vein
- has a darker (hypoechoic) wall
- is next to the liver, not in it
- cannot be traced to the middle hepatic ligament
- is a tubular structure
- does not connect to the portal vein
More images and explanation after the break!
Artifacts are ultrasound images on the screen that do not correspond exactly what is in the body. Artifacts can be useful in determining true anatomy:
1. The presence of some artifacts can help us to identify anatomy: e.g. “an aorta” is “the aorta” because it’s resting on the spine, which is “the spine” because it casts a shadow (what if the spine does not cast a shadow….?)
2. The absence of artifacts can also reveal pathology: e.g. in FAST with right hemothorax, loss of the mirror image of the liver above the diaphragm not only reveals the blood and superior aspect of the diaphragm, it also allows the vertebral column (above the diaphragm) to show up! The spine above the diaphragm is never seen because the normal aerated lung scatters all of the ultrasound energy above the diaphragm.
3. Both the real image and artifact arise because of certain assumptions that that ultrasound machine makes. When they are all met, you get a real image; when any assumption is not, well, you get an artifact. And thankfully, there are only four such assumptions. Here’s a quick review of them as we begin this series of what’s real and what’s not.
A pulse of ultrasound beam emitted by the transducer travels in a straight line, is reflected at an interface, and travels back to the transducer (exactly along the path it was emitted, only in the reverse direction)
All the returning echoes of the beam are presumed to have arisen only from the center (i.e. axis) of the beam and hence are displayed as such (i.e. along a vertical line on the screen that represents the axis)
The speed of ultrasound beam (emitted and/or reflected) is always and exactly 1540m/s
The intensity of the displayed echo is dependent on the acoustic properties and size of the interface where it is being reflected
And with that, we’ll make good use of what’s not really there to find out what’s really going on.
Bret Nelson and Mt. Sinai’s director of Disaster Preparedness and Prehospital Care, Kevin Chason, collaborated on this pilot study on use of Prehospital FAST and Aorta US which showed that paramedics can obtain and interpret these studies.
In this series, we cut to the chase and highlight our choice for the the top three articles on a given topic. Read on for the articles and brief discussion.
Three DVT articles that every emergency physician should know. What are they?
1) If there is any “must know” article for DVT or PE, this is it: commonly known as the Well’s Criteria, it provides a framework for the EP to approach any patient presenting with the the suspicion of DVT or PE. It is the ability to categorize patients into the different risk categories that we’re able to effectively use pre-test and post-test probability of a negative D-dimer to rule out the disease.
Wells PS, Anderson DR, Rodger M, et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med. 2003;349:1227.
2) With the introduction of bedside clinician performed ultrasound, EPs now have a tool to evaluate the proximal lower extremity veins themselves. While there is abundant literature suggesting the feasibility of an EP performed bedside ultrasound, this review article showed that properly trained EPs can accurately diagnose DVTs with a pooled overall sensitivity and specificity of 95% and 96% respectively. However, several limitations were highlighted with regards to the available literature – there is no standardization of the technique used, and the studies involved EPs already highly trained in ultrasound and so the results cannot be generalized to all EPs.
Burnside PR, Brown MD, Kline JA. Systematic review of emergency physician-performed ultrasonography for lower-extremity deep vein thrombosis. Acad Emerg Med. 2008;15:493-498.
3) This large RCT compares 2 point compression ultrasonography plus D-dimer with formal ultrasonography in symptomatic patients with suspected DVT. The rates of confirmed DVT at 3 months were similar in the 2 groups. This suggests that EPs can manage symptomatic patients suspected of having DVT with just 2-point compression ultrasound and D-dimer.
Bernardi E, Camporese G, Büller HR, et al. Serial 2-point ultrasonography plus D-dimer vs whole-leg color-coded Doppler ultrasonography for diagnosing suspected symptomatic deep vein thrombosis: a randomized controlled trial. JAMA. 2008;300:1653-1659.
Do you have other suggestions for studies? Comment below!
Visual Diagnosis Case from JEM. Bret and Ted discuss a case of appendicitis confirmed with ultrasound after CT was not conclusive.
X-Ray Stinks #1: Finger Injury
In this new series we will highlight cases where ultrasound proved more useful than x-ray.
A seven year old boy presented with distal phalanx pain, tenderness after a fall.
The following x-ray was performed:
What is your diagnosis? Can ultrasound help? How would you perform an ultrasound on such a superficial structure?
The following ultrasound of the distal finger was performed (probe marker towards fingertip):
What is your diagnosis now? Continue reading
Bret Nelson recently filmed a webinar on critical care ultrasound at Gulfcoast Ultrasound Institute in Florida. He discussed evaluation of the hypotensive patient, incorporating Scott Weingart’s RUSH exam as well as other literature on acute assessment of the heart, IVC, FAST exam, and pleura.
Information on the webinar is available at Gulfcoast.
References for a variety of hypotension evaluations are included below, as well as a few screenshots from the webinar!
- UHP protocol
- Trinity Protocol
- RCT of ultrasound in hypotension
- FATE: Focused Assessed Transthoracic Echocardiography
- FEER: Focused Echocardiographic Evaluation in Resuscitation
- CAUSE: Cardiac Arrest Ultrasound Exam
- RUSH: Rapid Ultrasound in Shock and Hypotension
- ACES: Abdominal and Cardiac Evaluation with Sonography in Shock
- RUSH: Rapid Ultrasound in Shock