Hepatobiliary Ultrasound

INTRODUCTORY SONOSITE HOW TO GALL BLADDER EXAM

 

GALL BLADDER (5MIN SONO)

GALL BLADDER FROM SONOGUIDE

 

Here is an excellent overview of gallbladder ultrasound from the guys at Ultrasound Leadership Academy.

Click on the link below and have a read...

 

Pearls and Pitfalls

1.  Duodenal Air: 

Because the second portion of the duodenum lies just behind the posterior wall of the gallbladder, air in the duodenum can inhibit the ability to successfully image the gallbladder.  Furthermore, this “slice” of sound actually has a thickness of 1.5 mm.  As it is directed towards the posterior wall of the gallbladder, some of this sound is reflected off the duodenum and the image produced is a combination of the two organs.  Because air can cause shadowing, it can appear that there is a gallstone lying on the posterior wall when in reality this is air in the second portion of the duodenum (Video clip 26 and 27).

2.  Renal Cyst: 

The kidney is closely related to the gallbladder and cysts in the superior pole of the kidney may be confused for the gallbladder.  This is one reason why it is important to view the gallbladder in both a short and long axis.  The renal cyst will appear the same in both axes, while the gallbladder elongates in a long axis.

3.  Ascites: 

Free intraperitoneal fluid, regardless of the etiology, will appear anechoic.  Be careful not to mistake ascitic fluid for pericholecystic fluid.  Ascitic fluid is typically located throughout the peritoneum, including Morrison’s pouch, whereas pericholecystic fluid is localized to the anterior side of the gallbladder.  Patients with ascites also have markedly thickened gallbladder walls not associated with an inflammatory process.  Keep in mind that fluid that is found posterior to the gallbladder can be the result of a ruptured gallbladder.

4.  WES Sign- Wall-Echo-Shadow: 

When a gallbladder is contracted around a gallstone, sometimes the only visualization of this is a shadow coming out of the liver.  This is due to the stone’s reflection that obscures the rest of the gallbladder.  The three layers of the gallbladder wall of the anterior gallbladder are generally seen, followed by the echogenic stone which is followed by the shadow caused by the stone.

5.  Patient Positioning: 

Typically the images are best obtained with the patient in a supine position, although rolling the patient into a left lateral decubitus position may be helpful.  This is thought to move the second portion of the duodenum away from the posterior wall of the gallbladder reducing the negative effect of duodenal air.

6.  Obtain Multiple Windows: 

The “X minus 7” approach refers to using an intracostal window in probes that have smaller footprints. This approach is especially useful in the morbidly obese patient.  Furthermore, it is important to view the gallbladder in both the short and long axes.  This can help in not mistaking the gallbladder for the IVC, renal cyst, or portal vein.  In general the gallbladder will appear in a perpendicular axis to the portal vein.  The “exclamation point sign” helps to draw this concept home.  When the gallbladder is in the long axis (the top of the exclamation point), the portal vein is in the short axis (the point of the exclamation point).

7.  Probe Orientation: 

With the indicator aimed towards the patient’s head the gallbladder is generally shown in the long axis.  As anatomical variation is common with the biliary system, this orientation may need to be adjusted in order to obtain this window.  Keep in mind that with biliary scanning the orientation of the gallbladder is with respect to how the organ appears on the screen, not necessarily the position of the probe on the patient.  The short axis of the gallbladder is typically found with the indicator towards the patient’s right

Renal Ultrasound

INTRODUCTION

The goal of bedside renal ultrasonography is to rapidly evaluate the patient presenting to the ED with flank pain, abdominal pain with hematuria or decreased urinary output to answer a few basic questions:

  • Is there hydronephrosis?

  • Unilateral or bilateral?

  • Is there fluid around the kidney?

  • Is the bladder distended?

  • Are stones seen?

  • Is the aorta normal?

 

THE BASICS

 

INTRODUCTORY SONOSITE RENAL VIDEOS

 

Point of care ultrasound for renal colic will be a more focused assessment of the kidney and our main area of interest will be the collecting system.

Unlike assessing the RUQ where we are looking for a hyperechoic stone with posterior shadowing, our goal with renal US is to identify indirect signs of ureterolithiasis such as hydronephrosis.  

Probe:  Low frequency curvilinear probe to allow for penetration deep into tissue for visualization of the entire kidneys and bladder. If you are having difficulties with significant rib shadowing, consider the phased-array probe for a smaller footprint allowing you to squeeze between th rib spaces.  

Positioning: Having the patient lay supine is a good place to start as it will allow you to scan both kidneys and the bladder fairly quickly. You can place the patient in alternating lateral decubitus positions if you are not obtaining adequate views of the kidneys supine which is often due to a large body habitus.

Where to Scan: Your scanning positions will be very similar to your FAST, so start as if you were performing this scan, placing the probe with marker towards the patient's head to obtain a long axis view of each kidney. You can try the short axis view as well by rotating the probe 90 degrees, but often the long axis view will be adequate for your evaluation. 

  • RUQ: Mid axillary line with the middle of the probe over the costal margin, using the liver as your acoustic window.

  • LUQ: Start mid axillary line with middle of probe over the costal margin, then move a little more superior and posterior and you should find your kidney here. Use the spleen as your acoustic window.

 

HYDRONEPHROSIS (5MIN SONO)

 

Grading of Hydronephrosis

 

Hydronephrosis: 

You will be looking for distention of the collecting system. In a normal kidney the renal pelvis may be minimally visible within the surrounding hyperechoic renal sinus (fat content makes it bright).

As obstruction of the ureter occurs, the renal pelvis becomes progressively dilated, leading to enlargement of the calyces and finally thinning of the renal cortex. This can be graded as as mild, moderate or severe and is quite subjective.

The above diagram gives you an idea of what you may expect to see on ultrasound when obstruction is present and a general visual grading guideline. Mild hydronephrosis will be difficult to pick up so it is essential to compare it to the opposite side and make sure you are not just appreciating a well hydrated patient. 

Severe Hydronephrosis

Severe Hydronephrosis

BLADDER VOLUME MEASUREMENT (5MIN SONO)

 

Ureteral Jets: 

Assessment of ureterovesicular jet dynamics, including velocity and how frequently they are occurring, as well as asymmetry, has a pretty good sensitivity for assessing for obstruction however this takes time and in the ED may not be that useful. If you are going to take a look, place the probe over a full bladder in a transverse orientation. You will be looking posteriorly at the UVJs. See references for more information on this topic. 

The Twinkling Artifact:

As we mentioned earlier, most ureteral stones will not be visualized directly on your bedside ultrasound, however color doppler may be useful to identify an obstructing stone that is initially invisible to your eye. You will be looking for the twinkling artifact, which has a 100% specificity for an obstructing stone! Note that you can assess for this both when you are performing ultrasound of the kidney as well as when you are assessing for ureteral jets (as the most common location of obstructing stone is at UVJ).

 

CONCLUSION

Renal ultrasound is better at identifying indirect signs of ureterolithiasis such as hydronephrosis, and not stone size and location, however we know that the majority of stones are initially managed with medical expulsion therapy.

Ultrasound of the renal system is also fast and can be performed at the bedside efficiently and accurately. With this in mind, it is reasonable to start with ultrasound for evaluation of renal colic as long as there are not complicating factors such as infected urine, severe pain or concern for more life threatening alternative diagnosis (be wary in older patients without h/o kidney stones or with multiple co-morbidities).  

A few more pearls:

  • In an elderly patient with acute flank pain, don't forget to perform a simultaneous exam of the aorta as this is a cannot miss diagnosis and may present similarly to renal colic

  • A renal cyst can appear as a anechoic structure within the kidney and mimic hydronephrosis. These do not originate from the renal pelvis and usually exist isolated in the renal parenchyma.

  • If something looks abnormal or if you are unable to discern the architecture of the kidney well, do not ignore it, work up further with more advanced imaging

CONTINUED LEARNING