Core-Renal Ultrasound

This core didactic session recap is devoted to renal ultrasound. Point-of-care ultrasound uses focused clinical questions to guide management, and our didactic session use focused clinical questions to guide discussions of key literature.

Discussants Vincent Roddy and Phillip Andrus led our group through a series of questions which bring the relevance of renal sonography home.

1. Can the degree of hydronephrosis predict stone size?

In an word, yes. In a retrospective study of 177 patients with documented stones on CT scans, ultrasonographers blinded to the CT results were able to predict stone size (>5mm or <5mm) based on the degree of hydronephrosis observed (1).

Hydronephrosis was defined as mild, moderate, severe

  1. Mild: Enlargement of calices with preservation of renal papillae
  2. Moderate: Rounding of calices with obliteration of renal papillae
  3. Severe: Caliceal ballooning with cortical thinning


Increasing degree of hydro associated with increasing proportion of ureteral calculi > 5mm (p < 0.001)
Take-home points:

  • Stone size is an important predictor of stone passage and clinical outcome; < 5mm likely to pass regardless of location
  • Current guidelines recommend triage of “medical expulsion therapy” for calculi between 5 and 10 mm; > 10mm often require surgical removal
  • Ultrasound sensitivity for detection of stones greater than 5mm is poor. With severe hydro over one-third had stones over 5mm and one third of THAT group had caliculi larger than 10mm (2)


  1. Goertz JK, Lotterman S. Can the degree od hydronephrosis on US predict kidney stone size? Am J Emerg Med 2010; 28:813-6.
  2. Preminger GM, Tiselius HG, Assimos DG, et al. 2007 guideline for the mgmt of ureteral calcul. J Urol 2007; 178:2418-34.

2. Should the bladder be included in the renal scan?

Yes – rapid ED renal ultrasound including images of the bladder might exclude distal obstruction and allows clinicians to focus on other diagnoses (1).

Ultrasound of the bladder also allows for the evaluation of the presence of “ureteral jets.”  Although clinically utility is debatable, a unilaterally abnormal ureteral jet can be suggestive of high-grade obstruction on the ipsilateral body side.  Ultrasound is useful in making this determination, though it is limited in its ability to determine stone location.  It is important to note that  normal ureteral jets cannot be used to exclude a diagnosis of renal colic.  (2).


  1. Wakins S, Bowra J. Validation of EP Ultrasound in Diagnosing hydronephrosis in ureteric colic. Emergency Medicine Australasia (2007) 19, 188-195.
  2. Sheafor D, Hertzberg B, et al. Nonenchanced Helical CT and US in the Emergency Evaluation of Patients with Renal Colic.


3. Can Emergency Physicians accurately diagnosis hydroneprhosis on bedside ultrasonography?

Yes, numerous studies have documented that ultrasound can accurately predict the degree of hydronephrosis as compared to that on CT scans (1-2) and that the degree of hydronephrosis is related to stone size (3).


  1. Gaspari RJ, Horst K. Emergency Ultrasound and urinalysis in the evaluation of flank pain. Acad Emer Med 2005; 12:1180-4.
  2.  Watkins S, Bowra J, Sharma P, Holdgate A, et el. Validation of EP ultrasound in diagnosing hydronephrosis in ureteric colic. Emerg Med Australas 2007; 19:188-95.
  3. Goertz JK, Lotterman S. Can the degree od hydronephrosis on US predict kidney stone size? Am J Emerg Med 2010; 28:813-6.

NYC Resuscitative Ultrasound Rounds

Citywide Critical Care Ultrasound

Were looking forward to the first citywide critical care ultrasound meeting. The idea for this gathering grew out of discussions between ED and ICU folks interested in critical care ultrasound who wanted to share experiences, interesting cases and ongoing research that would benefit from multicenter study.

Date: January 3, 2013
Time: 5pm
Location: 3 E 101st Street, Second Floor Emergency Medicine Conference Room New York, NY

Bubble test

We already know it is helpful to use ultrasound to guide placement of central venous catheters.

How can we use ultrasound to help confirm proper placement of an internal jugular catheter?

There are several methods which have been described:

  • Visualize the needle entering the vein (optimally in the long axis)
  • Visualize the guide wire in the vein
  • Visualize the tip of the triple lumen catheter in the right atrium, then pull back 2 cm
  • Bubble test (more on this below)

In addition there are non-ultrasound-related methods to confirm placement (but who cares about those?):

  • Chest x-ray
  • Blood gas drawn through central venous catheter port
  • Pressure transduction (quantitative- manometry)
  • Pressure transduction (qualitative- attach IV tubing and check height of blood column)

So let’s get back to that bubble test. In order to confirm that the catheter has been placed in the superior vena cava, inject 5-10 cc normal saline through the catheter while visualizing the right heart on a subxiphoid 4-chamber view.  When done right should look something like this :

Saline flush right heart from Sinai EM Ultrasound on Vimeo.

So this is a neat trick after the catheter is in, but the horse is out of the barn at that point. Ideally you should confirm proper venous placement prior to dilating the vessel and placing the central line. You could do this while the needle is in the vessel, but that’s a bit unstable. Instead consider using the long angiocatheter found in most central line kits to puncture the internal jugular vein.

After the flash (and ultrasound confirmation of venous puncture) advance the catheter and remove the needle. You then have an angiocatheter in the central venous system, which can be used for manometry, blood gas analysis, or the saline push necessary for the bubble test. Some people have used this angiocatheter during ACLS situations to administer a few doses of code medications in a shorter time than it would take to complete a “full” central line.

Once proper venous placement is confirmed, you can advance the guide wire through the angiocatheter and continue the procedure as normal.

For a great overview of central venous catheterization, check out this post by Haru Okuda and Scott Weingart at

Further Reading

Prekker ME, Chang R, Cole JB, Reardon R.  “Rapid confirmation of central venous catheter placement using an ultrasonographic “Bubble Test.” Acad Emerg Med 2010;17(7):e85-6. (PMID: 20653578)

Angles for Doppler

A prior post discussed the optimal imaging angle for 2D scanning.

Quick quiz: what is that angle?
45 degrees
90 degrees
180 degrees
360 degrees

In this post we’ll illustrate the optimal imaging angle for Doppler evaluation. Let’s start with basic Doppler physics.
Where to police officers situate themselves to aim a radar gun at speeding cars?

The maximal Doppler shift will be seen at 180 degrees. In fact at the instant the car passes the officer, (90 degrees) there will be zero Doppler shift. At that instant there is no movement between the object and the listener. So they aim the gun directly at the oncoming traffic, so the direction of their beam is parallel to the direction of [traffic] flow.

The image below illustrates Doppler shift of ultrasound reflected off a red blood cell:

  1. Top: A normal ultrasound wave
  2. Middle: Doppler shift reflected off the RBC moving toward the transducer (thus increasing the frequency of the returning wave)
  3. Bottom: Doppler shift reflected off the RBC moving away from the transducer (thus decreasing the frequency of the returning wave).

Thanks to for the image. Imaging at 180 degrees is impractical for diagnostic ultrasound, since the optimal B-mode imaging angle is 90 degrees. Therefore, most authorities recommend an imaging angle between 45-60 degrees for Doppler ultrasound imaging . If you are imaging a vascular structure at 90 degrees and getting no Doppler signal, try lowering your angle.

Physical exam

Is ultrasound the stethoscope of the future? Is it an extension of the physical examination? Will it replace the physical exam?


Point-of-care ultrasound is a diagnostic test. It is a rapid, bedside, noninvasive, accurate, diagnostic test, but still a diagnostic test. It can certainly augment data obtained through physical examination and medical interviews, and adds to information obtained by blood assays and radiology studies.

It is performed using FDA-approved medical devices by clinicians with specialized training. Images used for medical decision-making may be archived and shared with colleagues from multiple specialties. Quality assurance programs improve clinician accuracy and accountability. These are not physical examination characteristics. These are qualities of good diagnostic tests.

There is and will continue to be debate about this issue. Whether we think about point-of-care ultrasound as a diagnostic test or part of the physical examination has ramifications for training, documentation, archiving, and billing.

We recommend checking the guidelines relevant to your specialty and making up your own mind on this issue. In either camp some things remain constant: train well and use ultrasound to enhance the care you provide your patients.