Point of Care Ultrasound for Hernias

Originally Published: 2012-Feb-21

**This post was originally part of the ACEP Emergency Ultrasound Section’s Newletter in the Tips and Tricks section . The newsletter is located on the member only section of the site so I am posting here to make it more available.**

Patients commonly present with complaints of abdominal hernias and are frequent incidental findings in the emergency department. Incarcerated hernias can cause swelling, pain, and may require emergent surgical consultation if strangulated.

While an incarcerated hernia can be found on physical exam, ultrasound can assist in the management of these cases. Imaging the incarcerated hernia to identify the contents of hernia sac can help differentiate bowel from adipose tissue. As well, one can identify concomitant pathology such as free fluid, bowel wall thickening, pneumotosis coli, aperistalsis, and abnormal blood flow.

Diagnostic imaging is commonly described in many texts and articles; however, an additional step in the imaging protocol can help with the management of incarcerated hernias. Scan through the hernia sac and pay special attention to the abdominal wall for the break in the wall or the neck of hernia sac, this will allow planning for reduction. Identification of the neck allows the operator to direct the hernia contents toward the neck during manual reduction. It also allows the clinician to identify the size of the neck compared to the hernia contents.

Figure 1 shows an incarcerated ventral hernia containing small bowel. The neck can be identified by the defect in the abdominal wall. This hernia was successfully reduced by applying pressure from the lateral edge of the bowel loop toward the neck. Figure 2 shows the hernia post reduction containing only fat; the fascial defect is still visible.

While this large hernia had a midline neck, that is not always the case as demonstrated in Figure 3. The neck is visible and the hernia sac is laterally located. Evaluation of the hernia contents and neck location can aid in planning the reduction. Practice visualizing known hernias and the fascial defect or neck on patients with hernias that are not incarcerated or strangulated.

Figure 1: Incarcerated hernia with bowel and neck visualized

Figure 2: Post reductions fat containing hernia and neck are visualized

Figure 3: Small hernia lateral to the neck

Tips and Tricks for the Pelvic Views during the FAST Exam

Originally published: 2011-Apr-18

This is a short article that my colleagues and I wrote for the American College of Emergency Medicine Emergency Medicine Ultrasound Section April Newsletter.

The full newsletter can be found here.

The Focused Assessment with Sonography in Trauma or FAST exam is one of the most common Point of Care Ultrasound exams performed in the Emergency Department.  As discussed in numerous forums, the FAST (or E-FAST) exam can be used in multiple clinical scenarios beyond the traumatically injured patient.  We will discuss two common errors that can lead to the misdiagnosis of subtle findings.

The pelvic windows in the FAST exam are often scanned hastily if the RUQ and LUQ do not show free fluid; however, subtle pathology can be missed if the windows are not surveyed in a thorough manner.

The urine-filled bladder results in posterior acoustic enhancement, which can obscure pelvic structures and pathology posterior to the bladder.  This will be amplified if the far field gain is not appropriately adjusted.  Structures may appear significantly more hyperechoic, and free fluid can be missed due to wash-out from an overgained far field image.  Figure 1 is an example of missed pelvic free fluid due to posterior acoustic enhancement.  The overgained far field obscures the free fluid.

Sagittal view of the bladder with free fluid.  The posterior acoustic enhancement leads to an overgained far field despite the appropriate gain settings of the near field.  This small amount of free fluid, caused by a liver injury, was missed on initial evaluation.

Figure 2 demonstrates a similar transverse view of the bladder, but with improved far field gain.  Internal echoes are visible within the free fluid due to posterior acoustic enhancement; however, further reduction in far field gain may reduce visualization of anatomic structures.  Sonographers must strike a balance between adjusting the far field gain to adequately visualize free fluid while still identifying posterior structures and boundaries.  This highlights the need to remain vigilant in looking for small amounts of free fluid or other subtle findings.  Despite the reduced far field gain and improved image, the persistent artifact within the fluid could mask this pathology.  Appropriate imaging and assessment in the suprapubic window requires an understanding of both the pitfalls of posterior acoustic enhancement, as well as any limitations that can be encountered when correcting for this artifact.

Sagittal view of the bladder with subtle free fluid.  Although the far field gain is better than Figure 1, there are still echoes within the free fluid due to posterior acoustic enhancement.  This highlights the need to be vigilant for subtle findings in the FAST exam.

The second common error occurs while imaging the bladder in the transverse plane.   Sonographers commonly fail to adequately visualize the lateral edges of the structure.  One of the goals of transverse imaging is to evaluate for free fluid that is lateral to the bladder and may not be apparent on sagittal imaging.  Figure 3 demonstrates this potential pitfall.

Transverse view of the bladder with free fluid located laterally to the bladder.

Figure 4 shows a transverse view in which the lateral edges are not visualized.  This occurs most commonly either when the bladder is distended or when a small footprint transducer, such as the phased array or small curved array, is used.  If this occurs, the lateral edges need to be evaluated by scanning each half of the bladder separately on transverse imaging.

Transverse image of the bladder using a phased array transducer.  Due to the small footprint, the lateral edges of the bladder are not visualized and free fluid may not be visualized.

Single Operator Sterile Sheathing of an Ultrasound Probe for an Ultrasound Guided Procedure

Originally published 2011-Mar-07

During the care of critically ill patients either in the Emergency Department or other settings can involve the placement of Central Venous Catheters.  The literature supports the use of Ultrasound Guidance to prevent mechanical complications and increase success rates.  However, in addition to mechanical complications the patients can be at risk for delayed complications such as central line associated blood stream infections, CLABSI, or line infections.

One method to reduce this is the use of full barrier sterile precautions.  This includes placing the ultrasound probe in a sterile sheath to allow real-time guidance and maintaining the sterile field.  Many sterile sheaths are not designed for a single operator placement in the way they are folded and packaged.  This has lead to frustration, loss of sterility, infamous gel accident stories, and a reliance on an assistant.  However, there is a method to sheath the probe and maintain the sterile field as a single operator.

The procedure can be broken down into the following steps:

1. Place the probe upright in the holder
2. Place adequate nonsterile gel on the probe surface
3. Engage full barrier sterile precautions for the operator
4. Open the sterile sheath and place on non-dominant hand
5. Invert the sheath onto the dominant hand
6. Grasp the top of the probe
7. Unfurl the sheath onto the probe and cord
8. Secure the sheath in place and smooth out air bubbles
9. Place sterile gel on the sheath to allow imaging and procedural guidance

This was also published Academic Emergency Medicine in the Dynamic Emergency Medicine Section with an accompanying manuscript.  Trotter M, Nomura JT, Sierzenski PR. Acad Emer 2010;17:e153.

Tips and Tricks for Placement Confirmation of IJ Central Lines

Originally Published 2011-Jan-20

This is a short blurb that my colleagues and I wrote for the ACEP US Section Newsletter, January 2011 edition.

American College of Emergency Physicians Emergency Ultrasound Section Newsletter
Tips and Tricks Section January 2011

Christiana Care Health System Emergency Medicine Ultrasound Fellowship Program
DT Cook MD, JT Mink MD, JT Powell MD, PR Sierzenski MD RDMS, and JT Nomura MD RDMS

Placement of a central line is a common procedure in the resuscitation of critically ill patients in the Emergency Department. Real-time ultrasound guidance can reduce mechanical complications associated with central venous cannulation. This includes decreasing arterial puncture and increasing the rate of first pass success.

One complication of central venous catheter placement that may be detected by ultrasound guidance of vessel cannulation is misdirection of the catheter. We have all had internal jugular (IJ) catheters that travel into the subclavian or flip in a retrograde direction. We can employ ultrasound to gauge direction of the needle, location of the bevel and direction of the guidewire J-Tip.

When cannulating the IJ you can evaluate the placement of the guidewire to ensure it is placed correctly. The first step is to make certain that the wire has been placed in the IJ without puncture of the posterior wall. As described in several publications visualization of the wire should occur in a transverse and sagittal plane to ensure its location of prior to dilation.

You can then angle the transducer and trace the IJ and wire to the brachiocephalic vein (Figure 1). Depending on the maximal depth and frequency of your probe you may or may not be able to visualize the superior vena cava. The next step is to evaluate the ipsilateral subclavian vein to ensure the wire is not directed laterally (Figure 2). You have now ensured that the wire is at least directed to the ipsilateral brachiocephalic.

If you prep widely enough you can also repeat this on the contralateral side to ensure that you have not directed the wire to the contralateral subclavian or IJ.

Figure 1: View of the wire in the brachiocephalic vein. This probe does not have a low enough frequency and maximal depth to adequately view the superior vena cava in this patient. The probe is placed lateral and posterior to the clavicular head of the sternocleidomastoid muscle and directed toward the contralateral nipple.

Figure 2: The subclavian artery and vein are visualized without wire present in the subclavian vein. The probe is placed superior the clavicle and lateral to the clavicular head of the sternocleidomastoid muscle.