Emergency Ultrasound

Emergency medicine ultrasound has the basic goal of improving patient care. This chapter strives to provide a "visual blueprint" for the reader who uses emergency medicine ultrasonography in his or her practice. It is intended to serve as a practical imaging reference when an emergency screening ultrasound examination is being performed and assumes a basic knowledge and experiential base in ultrasound examinations. For practitioners without this prerequisite body of knowledge, it may provide useful information about the scope of the emergency screening ultrasound examination (ESUE).

Success in performing an ESUE is dependent on the physician's goal-directed approach to each examination. This demands that the physician use ultrasound to identify, confirm, or exclude specific sonographic findings that are consistent with specific disease states or life-threatening conditions.

Basic ultrasound information—including transducer recommendations, scanning protocols, anatomic schematics, and ultrasound images—are presented throughout the chapter. Applicable protocols are patterned after imaging guidelines of the American Institute of Ultrasound in Medicine as well as the authors' collective experiences. The issues of the efficacy, accuracy, and/or sensitivity of this modality are not debated; rather, a "visual blueprint" for ESUEs is provided. Once again, this chapter is not presented as a primary instructional tool, but rather as a rapid visual review for the physician trained in ESUE applications.

Information is presented about the following ESUE protocols:

1. Trauma: focused assessment with sonography for trauma (FAST)

2. Cardiac: echocardiography (ECHO)

3. Abdominal (gallbladder, aorta, and kidney)

4. Pelvic/endovaginal

Transducers

Sonography is performed using transducers of varying frequencies. Lower or higher frequencies are selected for more or less depth of penetration. Many manufacturers produce multifrequency transducers available with small or large footprints. The various transducers recommended for use in the ESUE are listed below (Fig. 19.1).

 Microconvex: This transducer has the advantage of a tight curvature and small footprint that allows for easy access between ribs and for subxiphoid imaging. This is an excellent transducer for the FAST, especially for the beginner, who may have difficulty scanning or interpreting with rib shadowing present. This probe is also helpful in the thin patients with a high-positioned gallbladder requiring intercostal windows for optimal imaging. These transducers are generally more expensive than the standard curve-linear transducer.

 Convex Array: Considered a standard abdominal transducer, it is used by many sonographers and provides wide near and far fields of view (ideal in evaluating the aorta). The long curved footprint of this type of transducer may make subxiphoid cardiac imaging difficult, as will the noted presence of "rib shadowing," which is inevitable with this transducer in scanning the right/left upper quadrants in the coronal plane. This is the transducer of choice for imaging the gallbladder at a frequency of 3.5 MHz; it is used by many vascular laboratories in evaluating the abdominal aorta. It is also the preferred transducer for renal ultrasound.

 Phased Array: This transducer is the transducer of choice for cardiac ultrasound. It results in a narrow near field of view. The image obtained is a true "pie-shaped" image. As a result, the phased array often has a small, flat footprint and is easy to maneuver between ribs. These transducers are frequently marketed in the 2.0- to 4.0-MHz ranges and will yield less resolution than the curved array transducers of higher frequencies. The advantage of this transducer is in scanning the obese patient who may be difficult to image during the FAST examination. The disadvantage is that the image quality is slightly less than that of geometrically steered (linear and curved array) transducers of the same frequency. This is not the preferred transducer for transabdominal pelvic sonography.

 Mechanical Sector: Many manufacturers still produce mechanical sector transducers. These provide a small footprint with a pie-shaped image and are usually much less expensive than phased-array transducers. Mechanical transducers are more likely to wear over time and tend to be less tolerant to incidental impacts (a common occurrence in the ED).

 Linear: This transducer is frequently used for superficial structures and vascular ultrasound. It usually is available in frequencies ranging from 5.0 MHz upward. It can be helpful in the very thin patient or the patient with an extremely superficial gallbladder.

Trauma Ultrasound

The focused assessment with sonography for trauma (FAST) is an organized series of sonographic windows or views that attempts to identify the presence or absence of fluid in anatomic potential spaces (e.g., pericardium or Morison's pouch) or anatomically dependent areas (e.g., pelvis, posteroinferior thorax, and splenorenal recess). It is, in fact, a cardiac and thoracoabdominal survey that allows the physician to identify or exclude immediate or potential life threats in the trauma patient. Though intended for the evaluation of the traumatized patient, the FAST examination and its components are also extremely valuable in the evaluation of several emergent complaints and clinical conditions.

Clinical Indications for the FAST Examination

Blunt abdominal trauma

Penetrating thoracic/abdominal trauma

Unexplained hypotension (trauma and nontrauma)

Evaluation of the pregnant trauma patient

Acute dyspnea with suspected pleural/pericardial effusion or tamponade

In its simplest form, the FAST examination uses four primary sonographic windows to evaluate the patient. It is recommended that these windows be scanned in sequence, but isolated views may be obtained when indicated (e.g., suspected pleural effusions in the dyspneic patient).

Required Views for the FAST Examination

1. Subxiphoid-cardiac window (subcostal view)

2. Right upper quadrant (Morison's pouch)

3. Left upper quadrant (splenorenal view)

4. Suprapubic window (pelvic view)

Recommended Transducers for the FAST Examination

 Microconvex

 Convex array

 Phased array

Most abdominal sonography is performed using transducers of 3.5 to 5.0 MHz. The FAST examination is an echocardiographic and thoracoabdominal examination. This presents the dilemma of using a transducer that can image all three of these areas but only with some sonographic compromise.

FAST Window 1: Subxiphoid-Cardiac (Subcostal View)

Technique

The patient is supine.

The transducer is directed under the xiphoid process toward the left shoulder in a horizontal plane (Fig. 19.2).

Direct the transducer indicator to the patient's right.

Pivot, sweep, and tilt the transducer to view of all four cardiac chambers.

Identify the heart, four cardiac chambers, and surrounding pericardium (Fig. 19.3).

Abnormal Findings

Hemopericardium (pericardial effusion): Dark black, anechoic region noted between the bright pericardium and the walls of the heart (occasionally internal echoes representing fibrin, clot, or cardiac tissue may be present) (Fig. 19.4).

Asystole: No cardiac activity present.

Hyperdynamic cardiac activity: Extensive cardiac contraction with maximal collapse of the cardiac chambers, often associated with tachycardia and hypovolemia.

FAST Window 2: Right Upper Quadrant (Morison's Pouch)

Technique

The patient is supine.

The transducer indicator is aimed toward the axilla in a coronal plane.

The transducer is directed as a coronal section through the body in the midaxillary line, extending from the 9th through 12th ribs. Start between the 11th and 12th ribs initially, then move cephalad or caudal to complete the evaluation (Fig. 19.5).

Identify the liver and right kidney interface. This region is the potential space known as Morison's pouch. Normally, these organs' surrounding tissues are in direct contact with one another (Fig. 19.6).

Evaluate the right diaphragmatic recess and the subdiaphragmatic recess.

Abnormal Findings

Hemoperitoneum: Dark black, anechoic region between the liver and right kidney or in the subdiaphragmatic recess (Fig. 19.7). May be positive with a ruptured ectopic pregnancy.

Right hemothorax: Anechoic (dark) region above the level of the diaphragm.

Solid organ injury: Solid organ injury such as hepatic and renal lacerations as well as organ rupture have been described but are beyond the scope of this chapter.

Hydronephrosis: Dilatation of the renal sinus with dark, anechoic fluid within the bright renal sinus (see "Renal Ultrasound," below).

FAST Window 3: Left Upper Quadrant (Splenorenal View)

Technique

The patient is supine.

The transducer indicator is directed toward the axilla in a coronal plane.

The transducer is directed as a coronal section through the body in the midaxillary to posterior axillary line extending from the 9th through 12th ribs. Start between the 11th and 12th ribs initially, then move cephalad or caudal to complete the evaluation (Fig. 19.8).

Identify the spleen and left kidney interface. This region is a physiologic potential space. Normally the surrounding tissues of these organs are in direct contact with one another (Fig. 19.9).

Evaluate the left diaphragmatic recess and the left subdiaphragmatic recess.

Abnormal Findings

Hemoperitoneum: Anechoic (dark) region between the spleen and left kidney or between the spleen and the diaphragm (Fig. 19.10).

Left hemothorax: Dark black, anechoic region above the level of the diaphragm (Fig. 19.11).

Solid organ injury: Solid organ injury such as splenic and renal lacerations as well as organ rupture have been described but are beyond the scope of this chapter.

Hydronephrosis: Dilatation of the renal sinus with dark black, anechoic fluid within the bright renal sinus (see "Renal Ultrasound," below).

FAST Window 4: Suprapubic

Technique

Sagittal View (Longitudinal)

The patient is supine.

The transducer is placed just above the symphysis pubis.

The transducer is directed into the pelvis with the transducer indicator oriented toward the patient's head (Fig. 19.12).

Identify the bladder (triangular in this view when fully distended), uterus (pear-shaped if present), and rectum (Fig. 19.13).

Transverse View

The patient is supine.

The transducer is placed about 1 to 2 cm above the symphysis pubis.

The transducer is directed with the transducer indicator oriented toward the patient's right, with the beam angled caudally into the pelvis (Fig. 19.14).

Identify the bladder (rectangular in this view when fully distended), uterus (oval hyperechoic structure if present) and rectum (Fig. 19.15).

Abnormal Findings

Hemoperitoneum: Anechoic (dark) regions between the bladder and uterus or the uterus and rectum or as loops of bowel floating lateral to the bladder in the transverse view and lateral or superior to the bladder in the sagittal view (Fig. 19.16).

Scan Pearls for the FAST Examination

Subxiphoid-Cardiac

1. When your view is obscured by gas, slide the transducer slightly to the patient's right subcostal region, using the liver as an echogenic window.

2. If you are unable to view the heart in the true subxiphoid or subcostal window, move to a parasternal long axis view (see "Cardiac Ultrasound (ECHO)," below).

3. A frequent mistake in imaging is to direct the transducer toward the spine rather than coronally to the shoulder. You will often require less than a 30 degree angle between the transducer and the skin.

4. Start imaging with the depth/scale setting at its maximum (e.g., 20 to 24 cm). This should allow you to image the anterior and posterior pericardium in your initial view. Gradually decrease the depth/scale (e.g., 14 to 18 cm) to fill the entire sector image with the heart as you continue to optimize your image.

RUQ and LUQ

1. The diaphragmatic recess includes a superior region, which is the inferior border of the right thorax, and an inferior region (subdiaphragmatic recess), which is the superior border of the abdomen. Fluid in the diaphragmatic recess can represent a hemothorax when located superior/cephalad to the diaphragm or a hemoperitoneum or subphrenic hematoma (inferior to the diaphragm) in the setting of trauma.

2. Identify the kidneys from the superior to the inferior poles in the coronal plane. It may seem easier at first to perform a short axis view; however, the sonographer risks missing early small fluid collections if only a middle renal transverse section is imaged.

3. If you are uncertain whether a finding is actually present, evaluate it in a second plane. To do this, turn the transducer 90 degrees from your initial transducer position and see if the finding is still noted on the image.

4. It is important to note that the LUQ is not synonymous to the RUQ; the spleen is not tethered to the diaphragm as the liver is by the coronary ligament. Sonographically we tend to see fluid collect in the left subdiaphragmatic area more than the right. This area should be evaluated.

Suprapubic

1. It is important to remember that the bladder is within the pelvis; therefore the transducer must be directed posteriorly and inferiorly to image the bladder and its neighboring structures.

2. When in the sagittal plane, simply rotate the transducer 90 degrees counterclockwise with the transducer indicator oriented to the patient's right, and you will transition to a transverse view.

Cardiac Ultrasound (ECHO)

Two-dimensional echocardiography (2D ECHO) can yield significant diagnostic information for the patient presenting with cardiac arrest, shock, shortness of breath, and a host of other complaints or physical findings. Although the physician can easily become intimidated by all the diagnostic possibilities that can be identified or potentially missed in performing echocardiography, one can, with experience, incorporate ED ECHO into the diagnostic armamentarium without becoming overextended.

It is important to note that, unlike abdominal sonography, cardiac ultrasound is by convention oriented with the transducer indicator for the display screen to the right of the screen (which will effectively be the patient's left). This may be a significant cause of initial confusion for many who have not performed echocardiography before. Most ultrasound systems today include cardiac presets that automatically reverse the orientation to the right of the display screen. The following section describes a sonographic approach for a correctly oriented image using standard cardiac windows.

Clinical Indications for ED Cardiac Ultrasound (ECHO)

Cardiac arrest, PEA

Penetrating thoracic/abdominal trauma

Unexplained hypotension or shock

Dyspnea

Acute myocardial infarction

Suspected aortic dissection

Specific pathologic states confirmed or excluded with ED ECHO include asystole (confirmation), cardiac activity (confirmation), pericardial effusion, and aortic root dilatation/dissection.

The sonographic windows for ED ECHO act as an extension of the subxiphoid view presented within the trauma/FAST examination. The ED ECHO utilizes cardiac windows that are familiar to cardiologists and sonographers alike. The four ED ECHO windows will allow the emergency physician to evaluate asystole, pericardial effusions, and the aortic root.

Required Views for Emergency Department ECHO

1. Subxiphoid (subcostal) (see "FAST Examination," above)

2. Parasternal long-axis view (PSLAx)

3. Parasternal short-axis view (PSSAx)

4. Apical four-chamber view (A4C)

Recommended Transducers for ECHO

 Phased array

 Microconvex

 Mechanical sector

ECHO Window 1: Subxiphoid-Cardiac (Subcostal View)

Technique

The patient is supine.

The transducer is placed inferior to the xiphoid process and directed toward the left shoulder in a horizontal plane. (The transducer indicator should be directed in the same orientation as the indicator mark of the screen; this is frequently to the patient's right in an abdominal preset, but it is toward the left in a cardiac preset) (see Fig. 19.2).

Pivot, sweep, and tilt the transducer to view all four cardiac chambers.

Identify the heart, four cardiac chambers, and surrounding pericardium (see Fig. 19.3).

Abnormal Findings

Hemopericardium (pericardial effusion): Anechoic (dark) region noted between the bright pericardium and the walls of the heart (occasionally internal echoes representing, fibrin, clot, or cardiac tissue may be present) (see Fig. 19.4).

Asystole: No cardiac activity present.

Hyperdynamic cardiac activity: Extensive cardiac contraction with maximal collapse of the cardiac chambers, often associated with tachycardia.

Scan Pearls for Subxiphoid-Cardiac

See "Scan Pearls for the FAST Examination," above.

ECHO Window 2: Parasternal Long-Axis View (PSLAx)

Technique

This assumes a leftward image orientation—e.g., transducer indicator to the right of the screen. This will effectively be toward the patient's head.

The patient is supine or in the left lateral decubitus (LLD) position with the left arm extended above the head for easier transducer access.

The transducer is placed in the fourth or fifth left parasternal intercostal space with the transducer indicator directed at the right clavicle or shoulder (Fig. 19.17).

Identify the right ventricle, left atrium, left ventricle, aortic valve, aortic root, aortic outflow tract, and surrounding pericardium (Fig. 19.18).

Abnormal Findings

Hemopericardium: Anechoic (dark) region noted between the hyperechoic (bright) pericardium and the walls of the heart (see Fig. 19.4).

Aortic root dilatation: An aortic root measurement greater than 3.8 cm is abnormal and should suggest either aortic dissection or aneurysm in the emergency patient with chest pain or back pain or in the appropriate clinical setting. Further evaluation is recommended.

Dilated descending aorta: The descending thoracic aorta can be seen in the far field in this view posterior to the left atrium. A descending thoracic aorta greater than 3.8 cm is suspicious for aneurysm or dissection and requires further evaluation.

Scan Pearls for the Parasternal Long-Axis View

1. A true parasternal long-axis view (a sagittal image through the heart) will visualize the aortic root within the image. If the aortic root is not present, you are likely in an oblique plane and will need to gently angle the transducer in either direction to optimize the image.

2. It is critical to make deliberate, slow, small adjustments of the transducer in imaging the heart, since even small movements at the skin surface can translate into large changes in beam angle at just 5 to 10 cm deep from the surface.

3. Normal spontaneous respiration is usually fine for cardiac imaging. Patients who are tachypneic can be very challenging, and verbally coaching the patient's breathing patterns is best. If you note a great deal of artifact due to lung interposition, place the patient in the left lateral decubitus position; have him or her inhale and slowly exhale while you scan. When you have an acceptable window, ask the patient to stop exhaling and hold his or her breath while you capture your images.

4. Remember that the parasternal long axis is approximated by a line running from the right acromioclavicular joint and the left antecubital fossa (when the arm is lying by the patient's side).

ECHO Window 3: Parasternal Short-Axis View (PSSAx)

Technique

This assumes a leftward image orientation—e.g., transducer indicator to the right of the screen. This will effectively be toward the patient's head.

The patient is supine or in the left lateral decubitus position.

From the parasternal long-axis position, rotate the transducer 90 degrees clockwise (to the patient's left) or place the transducer in the fourth or fifth left parasternal intercostal space in a line connecting the left clavicle/shoulder and the right hip (Fig. 19.19).

Identify the left ventricle (circular), right ventricle (crescent-shaped), and surrounding pericardium (Fig. 19.20).

Abnormal Findings

Hemopericardium: Dark black, anechoic region noted between the bright pericardium and the walls of the heart (see Fig. 19.4).

Dilated right ventricle: The right ventricle is normally a crescent-shaped structure; if this is a rounded, dilated structure, it suggests elevated right-sided pressures, as seen with pulmonary emboli and severe pulmonary hypertension.

Scan Pearls for the Parasternal Short-Axis View

1. The standard parasternal short-axis view is obtained with the image plane at the level of the papillary muscles. Visualization of the papillary muscles should ensure a true transverse section through the left ventricle and provides a prime location for the evaluation of left ventricular contraction and motion.

ECHO Window 4: Apical Four-Chamber View (A4C)

Technique

This assumes that a leftward image orientation is the standard sonographic approach.

The patient is supine or in the left lateral decubitus position.

The transducer is placed over the cardiac apex or the point of maximal intensity (PMI) with the beam directed toward the right clavicle/shoulder in a plane coronal to the heart. The transducer indicator is directed toward the left axilla (Fig. 19.21).

Identify the left ventricle, right ventricle, left atrium, right atrium, and surrounding pericardium (Fig. 19.22).

Abnormal Findings

Hemopericardium: Anechoic (dark) region noted between the hyperechoic pericardium and the walls of the heart (see Fig. 19.4).

Dilated right atria/ventricle: If the right atria/ventricle are rounded or appear rigid and poorly contracting, this may suggest elevated right-sided pressures as seen with pulmonary emboli and severe pulmonary hypertension.

Scan Pearls for Apical Four-Chamber View

1. See "Scan Pearls for the FAST Examination, Subxiphoid-Cardiac," item 4, above.

2. It is critical to realize the variance in the resting position of the heart. It is evident, using this view, that there can be relatively significant differences and acoustic windows from patient to patient with the four-chamber apical view.

Abdominal Ultrasound

The application of abdominal ultrasound in emergency medicine seems, for many physicians, self-evident. Abdominal aortic aneurysm (AAA), gallbladder disease, and renal colic are all common diagnoses in patients presenting to the ED. The ability to rapidly diagnose or exclude these disease states can decrease patient morbidity and mortality. The abdominal emergency screening ultrasound examination (ESUE) can aid in this diagnostic process.

The clinical indications for an abdominal ESUE may vary with each ED and ED physician. There are three specific pathologic states that we believe the proficient emergency physician should be able to identify: AAA, gallstones, and hydronephrosis. This series on abdominal ESUE presents the applications of gallbladder, aortic and renal ultrasound.

Required Views for Abdominal Ultrasound

1. Gallbladder (sagittal, transverse, oblique views)

2. Aorta (transverse, sagittal views)

3. Renal (coronal, sagittal views)

Gallbladder Ultrasound

Ultrasound of the gallbladder can be among the most rewarding ESUEs to perform. Patients can receive a rapid focused ultrasound to determine if gallstones or gallbladder pathology is the etiology of their pain or presenting symptoms, and they are often relieved to be given a visual presentation of their illness. No ESUE calls for more careful positioning of the patient than the gallbladder and biliary ultrasound. Position the patient to minimize bowel gas from your view, accentuate possible pathology, and verify suspected findings. This can be a technically difficult ultrasound to perform.

Clinical Indications for Gallbladder Ultrasound

Right-upper-quadrant pain

Jaundice/icterus

Epigastric pain

It is important to recognize the limited nature of gallbladder ultrasounds performed by emergency physicians. Thorough evaluation of the biliary tract is a routine component of a standard radiology abdominal ultrasound but can be technically and diagnostically difficult, especially in the patient with acute pain. For this reason, measurement of the hepatic and common bile ducts is not included as an initial key component to the basic gallbladder ESUE. Techniques for measurement of the common bile duct are reviewed below; these should be performed by an emergency physician proficient in abdominal ultrasound. Although the sonographic identification of gallstones may seem straightforward, the sonographic findings for cholecystitis can frequently be subtle.

Recommended Transducers for Gallbladder Ultrasound

 Convex array

 Microconvex

 Phased array

 Mechanical sector

Most abdominal sonography is performed using transducer frequencies of 3.5 to 5.0 MHz. In rare instances, lower or higher frequencies are needed for more or less depth of penetration.

Gallbladder Ultrasound Window 1: Sagittal View

Technique

The patient is supine or in the left lateral decubitus position. Other positions—including prone, right lateral decubitus, semierect, and standing—may be helpful in scanning the gallbladder.

The transducer is placed in the subxiphoid region with the orientation indicator directed toward the patient's head and swept below the right costal margin to approximately the midclavicular line (Figs. 19.23, 19.24).

Identify the liver, portal vein, common bile duct, hepatic artery, gallbladder, and main lobar fissure (spanning these two structures). Measure the thickness of the common bile duct when able (Fig. 19.25).

Scan through the gallbladder completely from the medial to lateral borders of the gallbladder.

Gallbladder Ultrasound Window 2: Transverse View

Technique

The patient is supine or in the left lateral decubitus position.

From the sagittal position, rotate the transducer 90 degrees counterclockwise to the patient's right and move along the right costal margin (Fig. 19.26).

Identify the liver, gallbladder, inferior vena cava, right kidney (if visualized), and common bile duct (if visualized) (Figs. 19.27, 19.28, and 19.29).

Abnormal Findings

Gallstones: Bright oval to round hyperechoic structure(s) within the gallbladder, often with a posterior shadow on ultrasound (Fig. 19.30).

Pericholecystic fluid: An anechoic stripe that borders the outer gallbladder wall and should be visualized in two views. This fluid is often but not necessarily circumferential (Fig. 19.31).

Thickened gallbladder wall: A gallbladder wall that measures 4 mm or more is considered abnormal.

Sonographic Murphy's sign: Tenderness of the gallbladder when compressed under direct visualization with the ultrasound transducer.

Dilated common bile duct (CBD): A CBD with an internal diameter greater than 4.0 mm is dilated; however, documented measurements up to 8.0 mm can be normal in the elderly. One rule of thumb is that 4 mm up to age 40 and thereafter an increase of 1 mm per decade represents the normal range.

Scan Pearls for Gallbladder Ultrasound

1. It is frequently necessary to have the patient take a deep breath and hold it to allow the gallbladder to descend into sonographic view.

2. Measure the anterior wall when evaluating wall thickness. The thickness of the posterior wall is often affected by "posterior enhancement"; therefore it may falsely appear thickened.

3. The duodenum is located medially to the gallbladder. It may be interpreted as a gallstone even by proficient sonographers if care is not taken to evaluate the gallbladder completely and to observe for peristalsis on areas suspected to be bowel.

4. If you suspect gallstones but do not visualize "shadowing," confirm that your focal point is at the area of interest and try changing the transducer frequency if possible (e.g., increase from 3.5 to 5.0 MHz).

5. If pericholecystic fluid is suspected but difficult to determine, it may be helpful to increase the frequency or convert to a linear transducer.

6. Most ultrasound systems provide a cinematic loop, or "cineloop," that will allow the sonographer to recall on average 20 to 40 images that occurred before the image was frozen. Scrolling through these images is helpful in identifying the cleanest and sharpest image of the CBD to measure.

7. The gallbladder tends to migrate inferiorly in elderly patients, so that it may lie significantly below the costal margin.

Abdominal Aorta Ultrasound

Ultrasound of the abdominal aorta is used to diagnose or exclude an abdominal aortic aneurysm (AAA). As the general population ages, the diagnosis of AAA should occur with more frequency, and the use of ultrasound of the abdominal aorta in the ED for patients with abdominal, back, or flank pain should also increase.

Clinical Indications for Abdominal Aorta Ultrasound

Abdominal, back, or flank pain

Pulsatile abdominal mass

Hypotensive patient with abdominal pain or distention

Early diagnosis of AAA can improve patient survival. When a patient is in shock, there is no bedside test superior to an ESUE of the aorta to diagnose an AAA. Since aortic aneurysms occur as both fusiform (most common) and saccular types, it is essential that the ESUE of the aorta include both sagittal and transverse components. It is generally accepted that an aortic measurement of greater than 3.0 cm in diameter is abnormal, with a significant risk of aortic rupture starting with measurements greater than 5.0 cm. This section illustrates the abdominal vasculature, which will aid in identification of the abdominal aorta and evaluation of AAAs.

Required Views for Abdominal Aorta Ultrasound

Transverse view

Sagittal view

Recommended Transducers for Abdominal Aorta Ultrasound

 Convex array

 Microconvex

 Phased array

 Mechanical sector

Abdominal Aorta Window 1: Transverse View

Technique

The patient is supine.

Place the transducer in the epigastrium with the transducer indicator oriented to the patient's right. Move down the abdominal aorta to the bifurcation (about the level of the umbilicus) (Fig. 19.32).

Identify the liver, aorta, inferior vena cava (IVC), superior mesenteric artery (SMA), splenic vein (SV), and "spinal stripe" at the level of the proximal aorta (Fig. 19.33).

Identify the IVC, aorta, and spinal stripe at the mid- and distal aorta.

Abnormal Findings

AAA: Anteroposterior measurements of more than 3.0 cm are suspicious for an aneurysm (Fig. 19.34).

Abdominal Aorta Window 2: Sagittal View

Technique

The patient is supine.

Place the transducer in the epigastrium with the transducer indicator oriented toward the patient's head. Move down the abdominal aorta to the bifurcation (about the region of the umbilicus) (Fig. 19.35).

Identify the liver, aorta, inferior vena cava (IVC), celiac trunk, and superior mesenteric artery (SMA) (Fig. 19.36).

Abnormal Findings

AAA: Anteroposterior measurements of more than 3.0 cm are suspicious for an aneurysm.

Scan Pearls for Abdominal Aorta Ultrasound

1. The ESUE of the abdominal aorta should begin in the transverse view, since this view provides the greatest amount of information and is essential for the diagnosis of a saccular aneurysm.

2. Measure the entire diameter of the aorta or aneurysm and not just the lumen or false lumen. Include measurements of the proximal, mid-, and distal aorta.

3. If a significant amount of bowel gas is present, sit the patient at 45 degrees and apply constant gentle pressure.

4. The IVC will generally collapse when you have the patient abruptly "sniff"—a result of the negative pressure transmitted to the venous system by this maneuver.

5. If pulsed Doppler is available, it may be used to discriminate between the highly pulsatile flow of the aorta and the low-amplitude rumble of the IVC.

Renal Ultrasound

Renal ultrasound can yield helpful diagnostic information for the patient presenting with abdominal or flank pain consistent with renal colic. Obstructive uropathy due to kidney stones is the principal pathology identified with renal ultrasound. However, it is not standard practice for emergency physicians to perform renal ultrasound to identify renal or ureteral calculi; rather, the kidneys are evaluated for hydronephrosis. The presence of hydronephrosis in the patient with renal colic is presumed to be a direct result of ureteral obstruction. There is no accurate means of determining the degree of obstruction by the presence of hydronephrosis.

Clinical Indications for Renal Ultrasound

Flank pain

Renal colic

Abdominal pain in the elderly

Hematuria

Costovertebral angle (CVA) tenderness

The diagnostic dilemma for many emergency physicians is how to effectively utilize the renal ESUE in the patient with suspected renal colic. Although hydronephrosis is the primary sonographic finding in renal ESUE, renal cysts, calculi, and renal masses may also be identified.

The recommended sonographic approach to the kidney is identical to that for the RUQ and LUQ windows in the trauma/FAST examination previously discussed. The coronal view allows the sonographer to visualize the right or left kidney from the superior to inferior poles. The renal ESUE is best interpreted when comparative images are obtained between the right and left kidneys. It is important to realize that many approaches to the renal system, described in other texts, may be useful at times; however, the coronal view is familiar to the emergency physician. For that reason it is our primary window for evaluating the kidneys on the renal ESUE.

Required Views for Renal Ultrasound

Coronal views (right and left)

Renal Ultrasound Window 1: Right and Left Coronal Views

Recommended Transducers for Renal Ultrasound

 Convex array

 Microconvex

 Phased array

 Mechanical sector

Technique

The patient is supine.

The transducer indicator is oriented toward the patient's head.

The transducer is directed as a coronal section through the body in the midaxillary to posterior axillary lines (Fig. 19.37). Begin scanning between the 9th to 11th ribs on the right and the 8th to 11th ribs on the left.

Identify the liver, right kidney, renal cortex (with pyramids), and central renal sinus (Fig. 19.38).

Identify the spleen, left kidney, renal cortex (with pyramids), and central renal sinus (Fig. 19.39).

Abnormal Findings

Hydronephrosis: Dilatation of the renal sinus with dark black, anechoic fluid within the bright renal sinus (Fig. 19.40).

Renal calculi: Bright hyperechoic oval/round structures within the cortex or renal sinus (posterior shadowing is often present).

Renal cyst: Anechoic structure often at the periphery of the renal cortex with a thin wall, and posterior acoustic enhancement.

Scan Pearls for Renal Ultrasound

1. If your machine has "dual" or "multi-image" modes, selecting this feature will allow you to make an on-screen side-by-side comparison of both kidneys.

2. Rib shadows will be evident with this coronal view. Have the patient hold his or her breath in inspiration and move the transducer a rib space higher or lower to visualize the kidney from the superior to the inferior pole.

Pelvic Ultrasound

Pelvic ultrasound is frequently used to evaluate the patient presenting with pelvic pain and/or vaginal bleeding, who may have a host of underlying clinical conditions. Among these are ovarian cyst, tuboovarian abscess, ovarian torsion, fetal demise, urinary retention, incomplete or threatened abortion, molar pregnancy, appendicitis, urinary tract infection, ureteral calculi, or pelvic inflammatory disease. However, the primary goal of the pelvic emergency screening ultrasound examination (ESUE) is to exclude an ectopic pregnancy. Pelvic ultrasound is accomplished with two different scanning techniques: transabdominal and endovaginal.

Pregnant patients presenting with abdominal pain or vaginal bleeding during the first trimester must have an ectopic pregnancy excluded. This is commonly accomplished in the ED setting by identifying an intrauterine pregnancy.

Clinical Indications for Pelvic Ultrasound

Pelvic/abdominal pain

Vaginal bleeding (pregnant or nonpregnant patient)

Suspected pregnancy

Scan Requirements for Pelvic Ultrasound

1. Transabdominal ultrasound (uses the bladder as an acoustic window): sagittal and transverse views

2. Endovaginal ultrasound (provides a wider field of view, with better definition of anatomy): sagittal and coronal views

Pelvic Transabdominal Sonography (TAS) Window 1: Sagittal View

Recommended Transducers for Pelvic TAS

 Convex array

 Microconvex

 Phased array

 Mechanical sector

Technique

The patient is supine.

Place transducer superior to symphysis pubis, with the transducer indicator directed toward the umbilicus (Fig. 19.41).

Identify the bladder (triangular), uterus, rectum, ovaries, and the vesicouterine and rectouterine pouches (pouch of Douglas) (Fig. 19.42).

Abnormal Findings

Free intraperitoneal fluid: Anechoic (dark) bands of fluid located in the vesicouterine and/or rectouterine pouch.

Pelvic Transabdominal Sonography (TAS) Window 2: Transverse View

Technique

The patient is supine.

From the TAS sagittal view, rotate the transducer 90 degrees counterclockwise or place it superior to symphysis pubis, directed in a line connecting the anterior superior iliac crests (gradually angle caudally) (Fig. 19.43).

Identify the bladder (rectangular), uterus (if present), rectum, ovaries, and the vesicouterine and rectouterine pouches (pouch of Douglas) (Fig. 19.44).

Abnormal Findings

Free intraperitoneal fluid: Dark anechoic bands of fluid located in the vesicouterine and/or rectouterine pouch.

Scan Pearls for Transabdominal Ultrasound

1. A full bladder allows better visualization of structures posterior to the bladder in transabdominal ultrasound. An empty/minimally filled bladder is preferred for endovaginal ultrasound.

2. A small amount of free fluid found in the posterior cul-de-sac of the pelvis can be physiologic.

Endovaginal Sonography (EVS) Window 1: Sagittal View

Technique

The patient is supine (lithotomy position).

With a latex condom/shield covering the transducer, place it into the vagina, directed toward the anterior fornix in a line through the umbilicus (Fig. 19.45).

The transducer indicator is directed up.

Identify the bladder (sliver), uterus, rectum, ovaries, and the vesicouterine (anterior) and rectouterine (posterior) cul-de-sacs (Fig. 19.46).

Abnormal Findings

Free intraperitoneal fluid: Anechoic (dark) bands of fluid located in the vesicouterine and/or rectouterine pouch.

Ectopic pregnancy: Extrauterine gestation may have an accompanying "pseudosac" (an anechoic fluid collection within the endometrial echo of the uterus) in the uterus (Fig. 19.47).

Endovaginal Sonography (EVS) Window 2: Coronal View

Technique

The patient is supine (ideally in the lithotomy position).

From the EVS sagittal view, rotate the transducer counterclockwise 90 degrees or, with a latex condom/shield covering the transducer, place the transducer into the vagina directed toward the posterior fornix in a line through the umbilicus (Fig. 19.48).

Identify the bladder (sliver), uterus (ovoid) (Fig. 19.49), rectum, ovaries (Fig. 19.50), and the vesicouterine and rectouterine pouches (pouch of Douglas).

Identify an intrauterine pregnancy if present (Fig. 19.51).

Abnormal or Positive Findings

Free intraperitoneal fluid: Anechoic (dark) bands of fluid located in the vesicouterine (anterior) or rectouterine (posterior) cul-de-sac.

Live intrauterine pregnancy: Greater than 5-mm gestational sac with a thick, concentric echogenic ring within the endometrial echo of the uterus and both of the following: fetal pole with cardiac activity.

Intrauterine pregnancy(IUP): Greater than 5-mm gestational sac with a thick, concentric echogenic ring within the endometrial echo of the uterus and one of the following: yolk sac, fetal pole, or double decidual sign (the decidua capsularis and decidua vera seen as two distinct hypoechoic layers surrounding the early gestational sac) (Fig. 19.52).

Abnormal IUP: Gestational sac greater than 10 to 12 mm without yolk sac, gestational sac greater than 16 mm without fetal pole, or definitive fetal pole without cardiac pulsation.

No definitive IUP: The uterus appears empty and no definitive ectopic pregnancy is visualized. Possible diagnosis includes early IUP, abortion, ectopic pregnancy.

Ectopic pregnancy: Greater than 5-mm gestational sac and thick, concentric echogenic ring outside the endometrial echo of the uterus and one of the following: definitive yolk sac, obvious fetal pole, cardiac activity.

Scan Pearls for Endovaginal Ultrasound

1. On insertion of the transducer, identify the bladder.

2. In the sagittal view, identify the endometrial stripe from the fundus of the uterus to the cervix. This is accomplished by tilting the probe (anteriorly to posteriorly) while maintaining a sagittal plane of the uterus.

3. Return to the fundus of the uterus in a sagittal view and slowly evaluate the right and then left borders of the uterus in the longitudinal axis.

4. Turn the transducer counterclockwise 90 degrees to enter the coronal plane. The uterus should appear oval in this view. Scan posteriorly to the cervix and then superiorly to the fundus of the uterus to exclude the presence of a bicornuate uterus.

5. If a pregnancy or intrauterine sac is identified, further evaluate with measurements and an assessment of fetal cardiac activity.

6. To evaluate the ovaries, begin with the patient's right ovary and scan initially in the longitudinal (sagittal) plane, then rotate the transducer counterclockwise 90 degrees and evaluate the ovary in the coronal plane. The ovaries ideally will be located anteromedially to the external iliac vessels. This is often only a guide to their location, and a methodical approach is often required to visualize both ovaries.

7. If the uterus is difficult to identify, withdraw the transducer slightly. A common error in EVS is inserting the transducer too far, thus bypassing the uterus and imaging only bowel.