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Summary![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
Point-of-care ultrasound (POCUS) is a bedside imaging protocol performed by clinicians as an extension of the physical examination. It is valuable in the emergency department (ED) due to its noninvasive nature, rapid deployment, and ability to be performed at the bedside, thereby not interrupting urgent care. It helps narrow differential diagnoses and guide urgent management by providing real-time imaging that correlates with clinical features. Unlike formal ultrasound, POCUS is focused on limited areas and objectives based on the most likely diagnosis. Foundational knowledge of ultrasound transducers, image generation, and acoustic windows is essential for performing POCUS. Common clinical applications include FAST and eFAST to detect intraperitoneal or pericardial free fluid and pneumothorax, abdominal aortic ultrasound to detect aneurysms, IVC ultrasound to help assess volume status, biliary POCUS to detect cholelithiasis and acute cholecystitis, and POCUS for early pregnancy to detect intrauterine pregnancy and perform an emergency fetal assessment. Specific protocols for heart and lung POCUS include focused cardiac ultrasound (FoCUS) to rapidly assess cardiac structure and function and basic lung ultrasound in emergency (BLUE) to rapidly diagnose common causes of dyspnea. POCUS is also commonly used for bedside evaluation of suspected deep vein thrombosis. Other uses of POCUS include genitourinary, bowel, soft tissue, and ocular evaluation. Negative or inconclusive POCUS findings cannot definitively rule out a diagnosis as results are operator-dependent.
See “Ultrasound” for more information on fundamental concepts applied to broader sonographic modalities, e.g., formal ultrasound, endoscopic ultrasound, and contrast-enhanced ultrasound.
Image generation![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
- Generating high-quality and reliably interpretable ultrasound images is essential for POCUS to aid clinical decision-making.
- Good image generation is reliant on the following:
- An understanding of basic ultrasound principles
- Proper transducer selection, placement, and manipulation techniques
- Use of appropriate image optimization strategies
- A patient-oriented approach that minimizes discomfort and enhances cooperation
- Once optimal images are generated, interpret POCUS findings alongside other clinical and diagnostic parameters according to each patient's individual context.
Transducers![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
Proper transducer (or probe) selection, placement, and manipulation techniques are essential for image generation and should be guided by the clinical picture and area of interest.
Transducer selection [2][3]
- High-frequency: generates high-resolution images of superficial structures, e.g., peripheral vessels, subcutaneous tissue, external organs
- Low-frequency: generates low-resolution images of deeper structures, e.g., abdominal and pelvic structures
- Small footprint: preferred for narrow acoustic windows, e.g., intercostal spaces
- Wide footprint: preferred for large acoustic windows and/or scanning areas, e.g., the abdominal cavity
Ultrasound transducers typically used for POCUS [2][3][4] | ||||
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Transducer | Description | Footprint | Frequency | Clinical applications |
Linear array transducer |
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Curvilinear array transducer |
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Phased array transducer |
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Endocavitary probe |
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Placement
To best visualize the area of interest, place properly oriented probes on an appropriate acoustic window that takes into account the ultrasound conductivity and acoustic impedance of the underlying tissues.
Orientation [8]
-
Indicators (orientation markers): used to orient the transducer along the standard planes of view while scanning
- On the probe: typically a groove or ridge on one side of the probe
- On the monitor: typically appears as a white or green dot on one side of the screen
-
Orientation conventions
- By POCUS convention, the monitor indicator should be on the left side of the screen.
- Standard planes of view
- Sagittal plane: Orient the probe so that its indicator points cranially.
- Transverse plane: Orient the probe so that its indicator points toward the patient's right side.
-
Confirm probe-to-monitor orientation: Do this prior to scanning to ensure accurate interpretation of spatial relationships and relative location of findings.
- Initially locate the probe indicator by inspection or palpation.
- Next, verify that movement occurring on the indicator side of the probe corresponds to movement seen on the indicator side of the monitor.
- Touch the indicator side of the probe surface with a gloved finger or apply gel to that side.
- If movement is seen on the opposite side of the screen to the monitor indicator, this typically means the probe indicator was incorrectly identified and the probe needs to be rotated 180° before placement.
If the probe indicator is identified correctly and the monitor is set to POCUS conventions, the left side of the screen should display structures seen on the indicator side of the probe.
Adhere to orientation conventions as much as possible to avoid misinterpretation of findings and medical errors.
Choice of acoustic windows [2][7]
- Choose acoustic windows with good ultrasound conductivity, e.g.:
- Fluid-filled bladder: to visualize pelvic viscera
- Intercostal spaces: to visualize the pleural space
- Liver: to visualize the RUQ and the heart
- Spleen: to visualize the LUQ
- Avoid areas with excessive intervening air, bone, or fat.
- Ensure sufficient ultrasound gel is used as an interface between the probe and skin.
Manipulation [9]
- There are five cardinal movements of the transducer that are required for most POCUS applications.
- These manipulations require movement of the transducer footprint in relation to the body and/or a change in the angle of insonation, i.e., the angle between the ultrasound beam and the area of interest.
Cardinal movements of the ultrasound transducer | |
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Technique | |
Sliding (sweeping) |
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Tilting (fanning) |
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Rocking |
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Rotation |
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Compression |
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Image optimization (knobology)![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
General principles [3][5][8][10]
- Ultrasound machines are typically equipped with factory presets for certain applications (e.g., preset for abdominal examination).
- The factory presets serve as a good starting point to visualize the desired target tissue.
- Knobology refers to the manual adjustment of the following knobs or features on the ultrasound machine to enable further image optimization.
Familiarize yourself with the ultrasound machine you will be using before conducting examinations.
Modes [3][5][8][10]
-
B-mode or brightness mode
- Most commonly used mode for POCUS
- Generates a grayscale 2D image
- The image optimization settings described below refer primarily to those required for B-mode ultrasound.
- M-mode or motion mode: Used to evaluate tissue movement (e.g., in pneumothorax) [11]
-
Doppler mode: Utilizes the Doppler effect to evaluate blood flow within an area of interest or differentiate static fluid collections (e.g., simple cyst) from dynamic fluid flow (e.g., aneurysm)
- Based on the application, the following Doppler modes may be used:
-
Color duplex ultrasonography provides color-coding of flow direction.
- Red: direction of flow is toward the transducer
- Blue: direction of flow is away from the transducer
Depth penetration (sonography) [3]
-
Background
- Depth penetration is the distance traveled by ultrasound waves to visualize the target tissue/organs.
- The depth traversed by ultrasound waves is depicted on the monitor, typically in centimeters.
-
Action: Adjust the “Depth” or “Zoom” knob to optimize visibility and image quality.
- An appropriate depth is one in which the image generated predominantly contains the area of interest.
- As increasing the depth of penetration decreases the spatial resolution, select the least depth required to adequately visualize the target tissue/organs.
- Increasing depth also decreases the frame rate.
-
Examples
- Assessment of superficial structures (e.g., thyroid ultrasound)
- Select a high-frequency transducer (e.g., linear array transducer).
- Decrease the depth penetration as needed.
- Assessment of a deeper organ (e.g., pancreas)
- Select a low-frequency transducer (e.g., curved array transducer)
- Increase the depth penetration as needed.
- Assessment of superficial structures (e.g., thyroid ultrasound)
The transducer frequency plays an important role in determining the depth penetration.
Gain (sonography) [3][8]
-
Background
- Gain is the magnitude of amplification of the ultrasound wave being reflected back to the transducer, and it determines the brightness of the image on the monitor.
- Increasing gain:
- Increases the reflected ultrasound wave and generates a brighter image
- Decreases the contrast and spatial resolution of the image
-
Action: Adjust the “Gain” knob to optimize the brightness and resolution of the image. [3]
- Hypoechoic structures (e.g., fluid) should appear black.
- Hyperechoic structures (e.g., bone) should appear white.
- Adjoining structures should be distinguishable.
Avoid increasing gain too much, as overgained images result in poor contrast between adjacent structures.
Focal zone (sonography) [3][5][12]
-
Background
- The focal zone (or focal plane) refers to the part of the ultrasound beam with the narrowest diameter.
- The lateral resolution of the image is best at the focal zone.
- The location of the focal zone is depicted (e.g., with an arrowhead) on the lateral border of the image on the monitor.
- Some machines have more than one focal zone.
- Action: Adjust the “Focus” knob so that the focal zone marker falls at the area of interest.
Image capture and analysis [3]
-
Freezing images
- Use the “Freeze” or “FRZ” button to pause the real-time image in order to:
- Closely inspect the frame
- Obtain measurements
- Save and print the frame
- With most devices, it is possible to rewind frames after freezing using the trackball or touchpad.
- Use the “Freeze” or “FRZ” button to pause the real-time image in order to:
-
Taking measurements
- Areas of interest may need to be measured in various planes.
- Use the “Caliper” button to obtain the straight-line measurement between two points and the “Trace” button to obtain curved line measurements.
- Use the trackball or touchpad to maneuver the cursor to the desired point of measurement and set the points using the “Enter” or “Set” button.
- Use the “Next” button to take another measurement.
- Depending on the selected mode of examination, areas, volumes, angles, and more advanced measurements can also be calculated.
-
Saving and recording images
- Use the “Store” button to save paused frames.
- Use the “Clips” button to obtain short recordings.
- The “Print” button may be used if a physical copy of the ultrasound is desired.
Transducer selection and knobology checklist![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
- Turn the ultrasound machine on.
- Select an appropriate ultrasound transducer.
- Select “B-mode” or “2D mode” (appropriate for most POCUS applications).
- Select an application preset (e.g., abdominal, cardiac).
- Confirm the orientation of the transducer.
- Select an appropriate acoustic window to visualize the area of interest.
- Place adequate amounts of a low-impedance gel on the area to be scanned or on the transducer.
- Ensure firm and direct contact between the probe and skin to minimize air pockets.
- Adjust depth to maximize the visibility of the area of interest on the screen
- Adjust gain to optimize the contrast of structures
- Choose the optimal focal zone
- Manipulate the transducer (e.g., sliding, tilting) to visualize all areas of interest throughout the necessary planes.
- Document any necessary measurements.
- Record and save all relevant images.
General troubleshooting![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
All views
- Apply gel liberally to fill any spaces or crevices between the probe and skin, e.g., skin folds, umbilicus.
- Ensure firm and direct contact between the probe and skin to minimize air pockets.
Abdominal and subxiphoid views
- Consider applying sustained pressure, if tolerated, to allow bowel gas to slowly displace from the field of view.
- To reduce discomfort and resistance from pressure applied, consider asking the patient to flex the hips and knees to relax the abdominal muscles.
- Ask patients to take a deep breath and hold it, if tolerated, to inferiorly displace subdiaphragmatic abdominal organs that are obscured by rib and lung shadows.
- Consider alternative imaging techniques for patients with:
Pelvic views
- If using a transabdominal approach, consider asking patients to defer urination until after the scan, if tolerated.
- If an empty bladder impairs visualization, consider the following:
- Repeat the examination after a period of hydration.
- For catheterized patients, consider temporarily clamping the catheter or instilling a small amount (e.g., 50 mL) of normal saline into the bladder.
- Switch to an endocavitary probe if appropriate and tolerated, e.g., during POCUS for early pregnancy.
Thoracic views
- Place the probe within the intercostal space to visualize thoracic structures whenever possible, and consider switching to a probe with a smaller footprint.
- To better visualize the heart, consider asking the patient to turn towards the left-lateral decubitus position if tolerated.
- Consider comparing lung findings with the contralateral lung at the same intercostal level to help determine if they are pathological.
Artifacts
- Distortion or attenuation of the ultrasound beam can result in artifacts, such as acoustic shadow, acoustic enhancement, and reverberation artifacts.
- Some of these can be useful for the interpretation of images (e.g., gallstones producing acoustic shadows).
- Others can lead to false-positive, false-negative, or indeterminate findings
- Anticipate and recognize artifacts based on the acoustic impedance of overlying structures.
- Adjust gain or change transducer placement to minimize interference of artifacts with visualization.
FAST and eFAST![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
FAST and eFAST are abbreviated scans that help with decision-making in selected patients with acute traumatic injuries. They do not replace clinical judgment or other imaging modalities in trauma (e.g., CT scanning, radiography). Always interpret results along with other diagnostic and clinical findings within the individual patient context. [6]
Definitions [6][7][13][14]
- Focused assessment with sonography for trauma (FAST): a rapid, point-of-care sonographic assessment of the abdomen and thorax of trauma patients to detect free fluid within the peritoneal, pericardial, and pleural cavities
- Extended FAST (eFAST): an extension of the FAST scan that includes evaluation for pneumothorax
Indications
FAST and eFAST can be performed by nonradiologist clinicians with appropriate training and experience.
- Initial evaluation of patients with blunt or penetrating trauma to the torso.
- Recommended for all hemodynamically unstable patients (as an adjunct to primary survey) [15]
- Can be considered in hemodynamically stable patients prior to CT [16]
- Reassessment of stable trauma patients who are being managed conservatively
Limitations [17]
- Low sensitivity for the detection of:
- Hemorrhage < 500 mL
- Injuries to the bowel, mesentery, retroperitoneum, or diaphragm
- Intervening air (e.g., bowel gas, subcutaneous emphysema) and fat (due to obese body habitus) can limit visualization.
- High false-negative rate, especially in hemodynamically stable patients [17][18]
- False positives are possible in patients with comorbid nontraumatic pleural, pericardial, or peritoneal effusions.
A negative FAST does not rule out an intraabdominal or intrathoracic injury.
General technique [7][17][19]
-
Patient position
- Typically supine (may be the only feasible position in unstable or critically ill patients)
- Trendelenburg position improves the likelihood of identifying free fluid in the upper quadrants.
- Reverse Trendelenburg or a seated position improves the likelihood of identifying free fluid in the pelvic view.
-
Preferred transducers
- Cardiac and abdominal (FAST): curvilinear transducer or phased array transducer [7]
- Lung (added for eFAST): linear transducer or curvilinear transducer
-
Sequence [6]
- Can be guided by clinical features (e.g., external evidence of trauma, area of maximum tenderness) and/or mechanism of injury
- The RUQ is often assessed first followed by a clockwise sequence through the subxiphoid, LUQ, and pelvic views.
- For advanced trauma life support (ATLS), the American College of Surgeons suggests starting with the subxiphoid area and then moving through the RUQ, LUQ, and pelvis. [19]
If possible, obtain two planes of view for each area to avoid missing small fluid collections.
Subxiphoid view [6][7][19]
- Area of interest: pericardial space
- Acoustic window: left lobe of liver
-
Technique
- Begin in the transverse plane (indicator pointing toward the patient's right side).
- Place the transducer on the subxiphoid space in the midline.
- Apply firm pressure posteriorly to direct the ultrasound beam behind the ribs.
- To bring the heart into view, tilt the transducer anteriorly and toward the left shoulder, while maintaining posterior pressure to avoid losing contact with the skin.
- Identify the pericardium in relation to the diaphragm and the beating cardiac chambers.
- Scan the entire heart from base to apex and anterior to posterior by tilting and rocking the transducer through the planes of section.
-
Troubleshooting
- Adjust gain so that the fluid within the cardiac chambers appears black.
- Use more of the liver as an acoustic window: Slide the probe toward the patient's right while rocking it toward the patient's left.
- Ask the patient to bend their knees or take a deep breath and hold it (see “General troubleshooting”).
- Findings: An anechoic (black) area between the hyperechoic pericardium and the myocardium represents a pericardial effusion.
Beware of false positives for free pericardial fluid: A hypoechoic area limited to the anterior apex that does not extend posteriorly to dependent regions of the pericardial space may represent periapical fat. Fluid in the pleural and peritoneal spaces may also be mistaken for pericardial fluid.
RUQ view [6][7][19]
- Main areas of interest (craniocaudally)
-
Additional areas of interest for free fluid
- Right paracolic gutter
- Inferior renal pole
- Acoustic window: liver
-
Technique
- Begin in the sagittal plane (indicator pointing toward the patient's head).
- Place the transducer subcostally or in one of the inferior intercostal spaces over the right anterior axillary line.
- Rotate the transducer so that it is parallel to the ribs, with the orientation marker pointing toward the vertebral end of the rib.
- Slide the transducer in an anteroposterior and/or cephalocaudal direction to locate and center the hepatorenal interface.
- Once it is identified, tilt and rock the transducer to assess for free fluid (anechoic areas) within all areas of interest.
- Angle the transducer superiorly to assess the right costodiaphragmatic recess and right subphrenic space.
- Angle the transducer inferiorly to assess the right paracolic gutter and inferior pole of the kidney.
-
Troubleshooting: to improve image generation and visualization
- Adjust gain so that the diaphragm and renal sinus fat appear white and fluid-filled structures such as the IVC or gallbladder appear black.
- If possible, ask the patient to take a deep breath and hold it.
- Findings: Anechoic or hypoechoic fluid collections within the areas of interest should be considered pathological in the setting of trauma.
LUQ view [6][7][19]
- Main areas of interest (craniocaudally)
-
Additional areas of interest for free fluid
- Left paracolic gutter
- Inferior renal pole
- Acoustic window: spleen
- Ideal patient position: Trendelenburg position
-
Technique
- Begin in the sagittal plane (indicator pointing toward the patient's head).
- Place the transducer in one of the inferior intercostal spaces over the left midaxillary line.
- Rotate the transducer so that it is parallel to the ribs, with the orientation marker pointing toward the vertebral end of the rib.
- Slide the transducer in an anteroposterior and/or cephalocaudal direction to locate and center the splenorenal interface.
- Once it is identified, tilt and rock the transducer to assess for free fluid (anechoic areas) within all areas of interest.
- Angle the transducer superiorly to assess the left costodiaphragmatic recess and left subphrenic space.
- Angle the transducer inferiorly to assess the left paracolic gutter and inferior pole of the kidney.
-
Troubleshooting: to improve image generation and visualization
- Adjust gain so that the diaphragm and renal sinus fat appear white and fluid-filled structures such as the aorta appear black.
- If possible, ask the patient to take a deep breath and hold it.
- Findings: Anechoic or hypoechoic fluid collections within the areas of interest should be considered pathological in the setting of trauma.
To assess the LUQ, place the transducer more cranially and more posteriorly than for the RUQ.
Beware of false positives for free fluid in the LUQ: Contained fluid collections (e.g., abscesses, cysts, loculations, accessory organs) or pleural fluid collections can be mistaken for intraperitoneal free fluid. [6]
Pelvic view [6][7][17][19]
- Areas of interest
- Acoustic window: bladder (ideally, fluid-distended)
-
Technique
- Begin in the transverse position (indicator pointing toward the patient's right side).
- Place the probe just superior to the pubic bone.
- Rock the probe caudally to identify the bladder, if not immediately visible.
- Tilt the probe cephalocaudally to scan through the areas of interest in the transverse planes.
- Rotate the probe 90° clockwise so that the orientation marker points cranially, and tilt the probe laterally to scan through the sagittal planes.
-
Troubleshooting
- Adjust gain settings as needed.
- If genitourinary trauma is suspected, avoid urethral catheterization or instilling saline into the bladder to improve visualization until urethral or bladder injury has been ruled out.
- Avoid applying pressure to the pubic bone if pelvic fracture is suspected.
-
Findings
- Anechoic or hypoechoic fluid collections within the pouch of Douglas should be considered pathological in the setting of trauma.
- Free fluid is most likely to be seen behind or above the bladder or uterus.
- Any free fluid within the pouch of Douglas in male patients is considered pathological.
Following ovulation and menstruation in women of reproductive age, a small amount (e.g., < 50 mL or ≤ 1 cm diameter) of anechoic free fluid in the pouch of Douglas may be physiological. Clinical correlation is essential.
Limited lung ultrasound [6][7][19]
Views to screen for pneumothorax in both lungs are added to the FAST components to make up the eFAST protocol. See “Lung POCUS” for other indications.
- Area of interest: pleural line
- Acoustic window: intercostal space
-
Transducer
- A high-frequency linear transducer is best suited to detect pneumothorax.
- Higher frequency (i.e., > 5 MHz) curvilinear transducers can be used if linear transducers are not available or if there is no time to change transducers.
-
Technique
- Place the transducer in the sagittal plane over the 2nd or 3rd intercostal space at the midclavicular line.
- Adjust focal zone, gain, and depth as needed.
-
Findings
- Normally, the visceral and parietal pleura slide over each other easily during respiration and B-lines are visible.
-
Sonographic signs of pneumothorax
- Absence of pleural sliding
- Lung point
- Absence of B-lines with or without prominent A-lines
- On M-mode: barcode sign (instead of seashore sign )
In hemodynamically unstable patients, an abbreviated scan as described here is acceptable to detect a large pneumothorax. In stable patients, multiple areas of the chest should ideally be scanned to detect a pneumothorax. [6]
Further management
- Pericardial free fluid: See “Management of cardiac tamponade.”
-
Intraperitoneal or intrathoracic free fluid in trauma: Obtain immediate surgical consult.
- Depending on hemodynamic stability, further diagnostic evaluation may be considered.
- Unstable patients should undergo emergency laparotomy.
- See also “Management of trauma patients,” “Approach to blunt abdominal trauma,” and “Approach to penetrating abdominal trauma.”
- Signs of pneumothorax on eFAST: See “Management of traumatic pneumothorax.”
In trauma patients, it should be assumed that free fluid within any of the potential spaces is pathological.
Abdominal aorta![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
POCUS is a key diagnostic tool in the acute evaluation of patients with suspected AAA. Although it has high accuracy, it does not replace clinical judgment, formal ultrasound, or CT scanning, especially if performed by an inexperienced practitioner. Always interpret results along with other diagnostic and clinical findings within the individual patient context. [6][20]
Indications [4][21]
-
Urgent
- Palpable pulsatile midline abdominal mass
- Abdominal bruit
- Unexplained acute abdominal, lower back, or flank pain
- Sudden abdominal, back, or flank pain in a patient with known AAA
- Undifferentiated shock
- Nonurgent: See “Screening for AAA.”
Technique [4][6][21]
Initial steps
- Patient position: supine
- Preferred transducer: curvilinear or phased array
- Ultrasound preset: abdomen
Identifying the area of interest
The area of interest is the abdominal aorta lying just anterior to the hyperechoic vertebral body and its acoustic shadow.
- Place the transducer in the subxiphoid region.
- Start in the transverse plane (indicator pointing towards the patient's right side)
- Press down firmly but gently until the area of interest is in view.
- Adjust depth so that the hyperechoic vertebral bodies are visible at the bottom of the monitor.
- Distinguish the aorta from the IVC using POCUS.
- Center the aorta on the screen.
Scanning the aorta
- Slide the transducer from the xiphoid to the umbilicus to visualize the entire abdominal aorta from the celiac artery to the iliac bifurcation.
- Proximal aorta (corresponds to the subxiphoid): subphrenic region, near the celiac artery
- Mid aorta: adjacent to the level of the renal arteries
- Distal aorta: below the renal arteries, up to the iliac bifurcation (typically found at the level of the umbilicus)
- Evaluate for any positive POCUS findings of AAA.
Inability to visualize the entire aorta from celiac artery to iliac bifurcation, e.g., due to overlying bowel gas, results in an indeterminate study.
Measurements
- Measure from outer wall to outer wall at the greatest width of the aorta.
- Ensure that the transducer is accurately aligned along or perpendicular to the aorta to avoid over- or underestimating the aortic diameter.
- Ideally, both anteroposterior and transverse diameters should be measured.
As an intraluminal clot may mimic the aortic wall, measuring only the inner lumen of the aorta may underestimate the size of the aorta.
Troubleshooting
- Consider asking the patient to bend their knees to help relax the abdominal muscles.
- If bowel gas obstructs the view
- Attempt to displace it: Rock the transducer back and forth while applying firm but gentle pressure over the area of interest.
- If attempted displacement is unsuccessful, consider obtaining lateral views.
- Consider additional color Doppler imaging for the following:
- Evaluating for luminal patency
- Distinguishing the aorta from adjacent structures (i.e., lymph nodes) [6][22]
Distinguishing between the aorta and the IVC using POCUS | ||
---|---|---|
Aorta | IVC | |
Wall appearance | Thick | Thin |
Response to pressure | Noncompressible | Easily compressible |
Response to respiration | Unchanged | Can be collapsible |
Pulsatility | ++ | + |
Typical location | Patient left | Patient right |
Findings
- Normal: A normal abdominal aorta should have a uniform appearance without thrombi or wall irregularities and a diameter < 3 cm from the celiac artery to the iliac bifurcation. [20]
-
POCUS findings of AAA [20]
- A diameter either ≥ 3 cm or ≥ 50% greater than the aortic diameter proximal to the dilation indicates an AAA. [21]
- Document the maximal size, shape, and location of the AAA.
- Note the location of the aneurysm in relation to the renal arteries and aortic bifurcation.
- If an aneurysm is present, assess for free fluid using the FAST technique.
- The presence of a luminal flap indicates aortic dissection.
- A diameter either ≥ 3 cm or ≥ 50% greater than the aortic diameter proximal to the dilation indicates an AAA. [21]
POCUS may miss small or saccular AAAs (e.g., due to intervening bowel gas).
Paraaortic lymph nodes and retroperitoneal masses can have a similar appearance to AAA.
Further management
- For a negative study: Consider other causes of symptoms (see “Acute abdomen”).
-
For confirmed AAA: See “Acute management checklist for AAA.”
- Stable patients, no sign of rupture: CT angiography with IV contrast of abdomen and pelvis, vascular surgery consult
- Unstable patients and/or rupture: immediate vascular surgery consult for endovascular or surgical repair
AAA may not be the cause of the presenting features. Corroborate imaging findings with clinical features and consider alternate diagnoses. [6]
In patients with negative or indeterminate POCUS findings, consider CT angiography if the pretest probability for AAA is high. [4][6]
Inferior vena cava![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
POCUS of the subcostal IVC is widely used as part of the assessment of volume status and prediction of fluid responsiveness, however, its accuracy and utility remain unclear. [23][24][25][26]
Clinical applications [17][25][27]
- Part of the multimodal assessment of intravascular volume status in patients with suspected hypovolemia (e.g., shock, dehydration), hypervolemia (i.e., fluid overload), or congestive heart failure [23]
- Estimation of fluid responsiveness in patients requiring fluid resuscitation (e.g., after a fluid challenge or passive leg raise test) [24][25][28][29][30]
- Noninvasive estimation of central venous pressure (CVP) in spontaneously breathing patients (e.g., to guide fluid management in critically ill patients) [29][31]
Interpret IVC ultrasound alongside other diagnostic and clinical parameters of volume status. Avoid using it in isolation to predict fluid responsiveness.
Technique [4][17][32]
Initial steps
- Patient position: supine
- Preferred transducer: curvilinear
- Ultrasound preset: abdomen
- Acoustic window: liver
Identifying the area of interest
The area of interest is the intrahepatic IVC as it flows into the RA.
-
Suggested starting point
- Start in the transverse plane (indicator pointing toward the patient's right).
- Place the transducer in the subxiphoid region at the patient's midline.
- Press down firmly but gently until the area of interest is in view: i.e., the intraabdominal vessels can be seen anterior to the hyperechoic vertebral body and its acoustic shadow.
- Adjust depth so that the hyperechoic vertebral bodies are visible at the bottom of the monitor.
- Distinguish the IVC from the aorta using POCUS and center it in the image.
- While keeping the IVC centered, rotate the transducer 90° clockwise (with the indicator now pointing cranially) to view the IVC in the sagittal plane.
-
Alternative starting point
- Start in the sagittal plane (indicator pointing toward the patient's head).
- Place the transducer in the subxiphoid region at the patient's midline.
- Slide and/or angle the transducer toward the patient's right side until the IVC is at the center of the image, taking care to distinguish the IVC from the aorta using POCUS.
-
Common endpoint
- Once the IVC is visible in the sagittal plane, rock the transducer cranially until the IVC-RA junction can be seen on the indicator side of the screen.
- Slide and/or angle the transducer to capture the IVC in the longitudinal section where it appears widest (i.e., the midline of the vessel).
Measurements
- If possible, follow the IVC in a cephalad direction to visualize the site at which it drains into the RA and the liver veins.
- Measure the IVC diameter at peak inspiration and expiration, ideally at either of the following sites:
Troubleshooting
- Consider rewinding the image after hitting “Freeze” to select images with both the widest and narrowest diameter of the IVC during the respiratory cycle.
- If visualization of the IVC is difficult, e.g., because of interposed bowel gas, consider obtaining lateral views.
- Turn the patient in the left lateral decubitus position.
- Place the transducer at the right midaxillary line and visualize the IVC through the liver.
- Consider switching to M-mode, as this may help to obtain precise measurements.
Findings [27][29][33]
- Normal maximal IVC diameter: ∼ 1.5–2.5 cm [17][34]
-
IVC diameter variation (caval index): percentage of change in IVC diameter over the respiratory cycle
- For spontaneously breathing patients : IVC collapsibility index (IVCc) = ([maximal venous diameter during expiration - minimal venous diameter during inspiration]/maximal vessel diameter) × 100% [27][35]
- For mechanically-ventilated patients : IVC distensibility index (IVCd) = ([maximal venous diameter during inspiration - minimal venous diameter during expiration]/minimal venous diameter during expiration) × 100% [36]
- Conditions that limit the reliability of caval indices to predict fluid responsiveness include: [17][37]
- Reduced venous return
- Increased intrathoracic pressure: e.g., dynamic hyperinflation, obstructive lung disease, mechanical ventilation with high PEEP
- Cardiac dysfunction: e.g., chronic right heart failure, cardiac tamponade, right-sided MI, tricuspid valve regurgitation
- Unpredictable respiratory pattern: e.g., variation in patient respiratory effort, use of mixed ventilator modes
- Others: increased intraabdominal pressure, vascular disease involving the IVC (e.g., stenosis, thrombosis, external obstruction)
- Reduced venous return
Interpretation of IVC ultrasound to estimate volume status [17][34] | ||
---|---|---|
Parameter | Findings suggestive of: | |
Volume overload | Volume depletion | |
Maximal IVC diameter |
|
|
IVC diameter variation [26][27][35][36] |
|
|
The absence of IVC diameter variability on respiration is suggestive of elevated central venous pressure (e.g., due to volume overload or right heart failure), while total IVC collapse suggests volume depletion. [6][32]
Ensure IVC measurements are taken in the midline of the vessel to avoid underestimating the diameter.
Further management
Management of patients with volume overload or depletion is based on the underlying etiology.
Gallbladder and biliary tract![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
Biliary POCUS does not replace clinical judgment or formal ultrasound. Always interpret results along with other diagnostic and clinical findings within the individual patient context. [6]
Indications [4][6]
- RUQ abdominal pain and/or mass
- Unexplained jaundice, ascites, or altered liver chemistries
- Fever of unknown origin
Technique [4][6]
Initial steps
- Patient position: supine; alternatively, left lateral decubitus position
- Preferred transducer: curvilinear
- Ultrasound preset: abdomen
- Acoustic window: liver
Although biliary ultrasound is best performed in the fasting state, do not delay examination if the patient presents with acute symptoms.
Identifying the area of interest [6]
The main area of interest is the gallbladder body and contents.
- Start in the sagittal plane (indicator pointing toward the patient's head).
- Place the transducer in the subxiphoid region at or slightly to the right of the patient's midline.
- Optimize depth and gain as needed.
- Locate the gallbladder by sliding the transducer along the right costal margin (subcostal sweep).
Avoid confusing the gallbladder with other fluid-filled structures in the area, e.g., portal vein, IVC, liver or kidney cysts, abscesses. Scan in multiple planes or use color doppler if there is doubt. [6]
Troubleshooting
- Ask the patient to breathe deeply and hold their breath in inspiration, if feasible.
- If the lower liver margin cannot be visualized, use an intercostal approach.
- Place the transducer in one of the inferior intercostal spaces, parallel to the ribs.
- Ensure that the orientation marker points toward the vertebral end of the rib.
- Slide the transducer from the sternal border toward the patient's right side to locate the gallbladder.
The gallbladder may be difficult to identify because it contracts in the postprandial state and its position is variable. If the gallbladder cannot be identified or adequately assessed on POCUS, rescan the patient after 6–8 hours of fasting in nonurgent cases or obtain a formal abdominal ultrasound.
Scanning the gallbladder [6]
-
Longitudinal plane (long axis)
- Rotate the transducer to align with the long axis of the gallbladder so that the fundus appears on the right side of the screen.
- Tilt and/or slide the transducer to visualize the entire gallbladder.
-
Transverse plane (short axis)
- Rotate the transducer so that the orientation marker points toward the patient's right side.
- Tilt and/or slide the transducer to visualize the entire gallbladder, from fundus to neck.
-
Examination
- Assess for gallstones, gallbladder wall thickening, pericholecystic fluid, and sonographic Murphy sign (see “Pathological findings and further management” for details).
- If cholelithiasis is suspected, change the patient's position and evaluate for movement of the intraluminal echogenic foci.
Measurements [4][6]
-
Gallbladder wall thickness
- Measure the thickest portion of the anterior gallbladder wall.
- Gallbladder wall thickness is normally ∼ 3 mm in the fasting state and ∼ 1 mm in the distended state. [38]
-
Gallbladder diameter
- Consider measuring the anteroposterior diameter of the gallbladder in the transverse plane.
- Measurements of the gallbladder diameter are of limited value because the size of the gallbladder is highly variable.
- Gross distension (anteroposterior diameter > 4–5 cm) may indicate biliary outflow obstruction (e.g., due to acute cholecystitis or choledocholithiasis).
Pathological findings and further management [6]
Cholelithiasis [39]
-
Findings
- Highly echogenic intraluminal foci
- Strong posterior acoustic shadowing
- Movement of the echogenic foci on repositioning the patient (rolling stone sign)
- Further management: See “Acute management checklist for biliary colic.”
Biliary sludge, which can cause biliary colic, is seen on ultrasound as low-level echogenic material in the dependent portion of the gallbladder. Biliary sludge moves slowly on repositioning the patient and does not cause posterior acoustic shadowing. [40][41][42]
A gallbladder polyp can be differentiated from a gallstone as it does not cast a posterior acoustic shadow and does not move on repositioning the patient. [6]
Acute cholecystitis [6][43]
-
Findings
- Gallbladder wall thickening > 3–5 mm [6][44]
- Gallbladder distension (8–10 x 4–5 cm) [43][45]
- Gallbladder wall edema (sometimes referred to as the double-wall sign): The innermost and outermost layers appear hyperechoic, while edematous tissue between these layers appears as a hypoechoic layer.
- Sonographic Murphy sign
- Pericholecystic free fluid: hypoechoic region around the gallbladder
- Intraluminal gallstones and/or biliary sludge may be present.
- Further management: See “Acute management checklist for acute cholecystitis.”
Do not forget to rule out other life-threatening causes of epigastric pain (e.g., AAA, MI) even in patients with POCUS findings consistent with acute cholecystitis. [6]
Early pregnancy![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
Basic POCUS for early pregnancy is a limited study focused on the presence of an intrauterine pregnancy (IUP). It does not replace clinical judgment or formal ultrasound. Always interpret results along with other diagnostic and clinical findings within the individual patient context. [6]
Indications [6][46]
- To confirm the presence of, i.e., rule in, an IUP in first-trimester patients with any of the following symptoms suggestive of ectopic pregnancy:
- Acute lower abdominal pain
- Abnormal vaginal bleeding
- Syncope
- Signs of hemodynamic instability of no obvious etiology
- Identification of an IUP significantly reduces the likelihood of ectopic pregnancy, unless the patient has risk factors for heterotopic pregnancy, e.g., in vitro fertilization, previous ectopic pregnancy, or tubal disease. [6]
- See “Diagnostics for ectopic pregnancy.”
Obtain β-HCG in symptomatic patients at risk of early pregnancy, regardless of contraception use, followed by sonographic evaluation for IUP if positive.
Limitations
- It is beyond the scope of basic POCUS to assess other pelvic organs (e.g. ovaries, adnexa, uterus) or pregnancy viability beyond the presence of fetal heart activity.
- POCUS is not sensitive enough to rule out IUP or ectopic pregnancy.
- Accuracy is further limited in patients who have had pelvic surgery involving the vaginal canal or the rectum.
- If the diagnosis is uncertain or other structures need evaluation, obtain a formal ultrasound.
Technique: transabdominal approach [6]
Initial steps
- Patient position: supine
- Preferred transducer: curvilinear
- Ultrasound preset: abdomen
- Acoustic window: full bladder
Identifying the areas of interest
- Start in the sagittal plane (indicator pointing toward the patient's head).
- Place the transducer at the midline, just above the pubic symphysis.
- Identify the fluid-distended bladder and optimize depth and gain as needed.
- Locate the uterus posterior and inferior to the bladder.
- The vaginal mucosa appears as a hyperechoic stripe (vaginal stripe) surrounded by hypoechoic walls.
- Follow the vagina in a cephalad direction to identify the uterus, which appears as a pear-shaped organ.
- Identify the endometrial stripe, which appears as :
- A central hyperechoic line toward the end of the cycle
- A central hypoechoic line during the early cycle
- The thick-walled hypoechoic myometrium surrounds the endometrium.
The endometrial stripe is the initial area of interest for POCUS to rule in an IUP.
Scanning the uterus
- Longitudinal plane
- Transverse plane
-
Examination
- Look for sonographic signs of IUP.
- Evaluate for free fluid within the pouch of Douglas.
Following ovulation and menstruation, a small amount (≤ 1 cm in diameter) of anechoic free fluid in the pouch of Douglas is considered physiological. [22]
Technique: transvaginal approach [6]
The field of view on a transvaginal ultrasound is limited, and specialized training is required to adequately perform and interpret a transvaginal ultrasound.
-
Patient position
- Lithotomy position
- Alternatively, supine with flexed hips and knees
- Transducer: endocavitary
-
Initial steps
- Ideally, the bladder should be empty.
- Apply the low-impedance ultrasound gel inside the disposable sleeve for the transvaginal transducer.
- Apply lubricant liberally outside the sleeve.
-
Scanning technique: Scan the uterus in longitudinal and coronal planes.
- Slowly insert the transducer (with the indicator pointing ventrally) using gentle pressure
- Advance until the probe tip makes contact with the cervix and uterine tissue can be seen on the monitor.
- Sweep the transducer to each side to obtain longitudinal views.
- Gently rotate the transducer 90° counterclockwise (indicator pointing towards patient right) and tilt anteroposteriorly to obtain additional coronal views.
- Once the endometrial stripe is identified, look for sonographic signs of IUP throughout the planes of interest.
- Evaluate for free fluid within the pouch of Douglas.
Patients undergoing transvaginal ultrasound should have a chaperone present. [6]
Avoid color doppler ultrasound in the first trimester because of possible risks to the fetus. [47]
Troubleshooting
See also “Pelvic views” in “General troubleshooting.”
-
Transabdominal approach
- Ensure the bladder is full
- If the bladder cannot be filled, or structures are not visible despite a full bladder, switch to an endocavitary probe if available and tolerated by the patient.
-
Transvaginal approach
- Use lubricant liberally.
- Ensure no air pockets are present between the probe and the sleeve.
- Patients may be more comfortable inserting the probe themselves.
- For patients in the supine position with flexed legs in whom anterior visualization is difficult, consider placing a pillow under the patient's sacrum.
Sonographic signs of IUP [47]
In chronological order of appearance:
-
Gestational sac: the earliest sign of a possible IUP
- A small, anechoic spherical structure within the endometrial cavity (varies in size depending on gestational age)
- Identifiable by 4.5–5 weeks of gestational age (may only be 2–3 mm in size)
- Not a definite sign of IUP if seen in isolation [47]
- Endometrial thickening around the gestational sac (decidual reaction) may be visible.
-
Double decidual sac sign
- A hypoechogenic center surrounded by two concentric echogenic rings within the uterine cavity
- Increases the likelihood of an IUP, but may be absent in up to a third of patients
-
Yolk sac: the earliest definitive sign of an IUP
- A 3–5 mm spherical structure with an echogenic rim eccentrically located within the gestational sac
- Identifiable by ∼ 5.5 weeks of gestational age
-
Fetal pole (embryo): a definitive sign of an IUP
- An echogenic thickening attached to the inner wall of the yolk sac
- First visible at ∼ 6 weeks of gestational age when it has reached a size of ∼ 1–2 mm [47]
-
Fetal heart activity: a definitive sign of a viable IUP
- May be identifiable as early as ∼ 6 weeks of gestational age
- Best evaluated in M-mode. See “Fetal assessment in emergencies.”
Only confirm IUP if definitive signs are present, i.e., gestational sac PLUS either yolk sac, fetal pole, or fetal heart activity, and that these can be seen implanted within normal endometrium and myometrium. If the diagnosis is uncertain, obtain a formal ultrasound.
The inability to visualize an IUP on both transabdominal and transvaginal ultrasound at the β-hCG discriminatory level strongly suggests ectopic pregnancy.
The absence of IUP in a pregnant patient with hemodynamic instability and/or POCUS evidence of intraperitoneal free fluid strongly suggests ruptured ectopic pregnancy. This is a medical emergency requiring acute stabilization and definitive surgical treatment without delay.
Further management
- IUP confirmed: Consider other causes acute symptoms besides ectopic pregnancy unless risk factors for heterotopic pregnancy are present
-
Positive pregnancy test and no sonographic signs of IUP
- Hemodynamically stable patients: formal ultrasound to confirm POCUS findings
-
Hemodynamically unstable patients
- Urgent obstetric and gynecology consult for emergency surgery
- Do not delay stabilization for formal ultrasound.
- See “Acute management checklist for ectopic pregnancy” and “Management of ruptured ectopic pregnancy.”
Fetal assessment in emergencies![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
An emergency physician may use bedside POCUS for patient triage and/or preparation for surgery; it is not a substitute for the biophysical profile. [48][49]
Assessment goals
- Identify cardiac activity.
- Obtain fetal heart rate (usually with M-mode).
- Determine fetal orientation in utero.
-
Assess gestational age.
- First trimester: crown-rump length (CRL)
- Second and third trimesters: biparietal diameter (BPD) [50]
- Note the presence or absence of fetal activity.
- Estimate amniotic fluid volume qualitatively or with the amniotic fluid index (AFI).
Technique
- Use a 3–5 MHz curvilinear probe.
- Position the patient supine (consider left uterine displacement in advanced pregnancy).
- Position the probe above the symphysis pubis or over the gravid uterus; transverse and/or longitudinal views may be used.
- Determine fetal heart rate. [49][51]
- Sweep and/or fan the probe to find the best view of fetal heart activity.
- Hold the probe in this position and change to M-mode (a sinusoidal wave pattern will be visible).
- Freeze the screen.
- Activate the built-in fetal heart rate calculator; a caliper will appear.
- Use the caliper to measure the peak-to-peak distance between waves.
- Record the machine-calculated heart rate.
- Consider adding components of first-trimester ultrasound or second-trimester ultrasound such as CRL, BPD, and AFI, as needed.
Focused cardiac ultrasound (FoCUS)![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
FoCUS is an adjunct to the physical examination that facilitates rapid diagnosis and decision-making in specific clinical situations; it is not a substitute for formal echocardiography. [52][53]
Indications [54]
- Chest trauma
- Dyspnea
- Hypotension
- Chest pain
- Cardiac arrest and resuscitation
- Syncope or presyncope
- Ultrasound-guided procedure (e.g., pericardiocentesis)
Assessment goals [54][55][56]
- Global LV size and function
- Global RV size and function
- Volume status
- Pericardial disease or effusion [57]
- Gross cardiac abnormalities
Findings are typically reported qualitatively (e.g., dilated vs. nondilated, hyperdynamic or hypodynamic vs. normal). [52][56]
Essential views [57][58]
All views are typically obtained using a phased array probe (1–5 MHz) with the patient in the supine position. Unlike most POCUS, the monitor indicator is usually on the right side of the screen for FoCUS.
Parasternal long axis view (PLAX)
- Definition: an ultrasound view of the heart along its long axis (i.e., base to apex) as seen from the left sternal border
-
Technique
- Place the probe to the left of the sternal border at the 3rd or 4th intercostal space (nipple line).
- Orient the probe indicator to the right shoulder.
-
Assessment goals
- RV and LV size
- LV systolic function
Parasternal short axis view (PSAX)
- Definition: an ultrasound view of the heart along its short axis (i.e., perpendicular to the long axis) as seen from the left sternal border
-
Technique
- From the PLAX view, rotate the probe 90° clockwise so that the probe indicator points to the left shoulder.
- Tilting the probe provides views of multiple structures including mid-LV, aortic valve, and mitral valve.
-
Assessment goals
- LV systolic function
- Relative size of the LV and RV
- Ventricular wall hypertrophy
Apical four-chamber view (A4CH)
- Definition: an ultrasound view of all four chambers of the heart as seen from the cardiac apex
-
Technique
- Palpate the point of maximum impulse.
- Place the probe over the point of maximum impulse.
- Orient the probe indicator to the patient's left.
- Point the probe cephalad with a shallow angle.
- Slide the probe until the intraventricular septum is at 12 o'clock.
-
Assessment goals
- RV size and systolic function
- Mitral and tricuspid regurgitation
- Pericardial effusion
Subcostal four-chamber view or subxiphoid view
- Definition: an ultrasound view of all four chambers of the heart as seen from the upper abdomen just inferior to the xiphoid process
- Technique: a phased array or curvilinear probe can be used; see “Subxiphoid view” in “FAST examination” for details.
- Assessment goal: pericardial effusion
The subcostal four-chamber view is useful if other views of the LV are suboptimal, particularly in mechanically ventilated patients. [59][60]
Subcostal inferior vena cava (SIVC)
- Definition: an ultrasound of the IVC as seen from the right subcostal region of the abdomen
- Technique: See “IVC ultrasound.”
- Assessment goal: volume status
Placing the patient in the left lateral decubitus position or putting pillows behind the right shoulder may improve visualization of cardiac structures. [58]
Findings
Global LV size and function [57]
- Best views: PLAX, PSAX, A4CH
-
Normal findings
- Ventricular walls thicken and nearly touch during systole.
- Anterior mitral valve leaflet moves freely and remains close to the septal wall during diastole (best seen on PLAX).
-
Abnormal findings [57][61]
- Hyperdynamic LV suggests:
- Hypovolemic shock (especially if LV is small)
- Sepsis
- Obstructive shock
- Hypodynamic LV suggests:
- Decompensated chronic heart failure, e.g., large atrial volumes and/or ventricular volumes, hypertrophied LV walls
- Myocardial infarction
- Sepsis-induced cardiac dysfunction
- Hyperdynamic LV suggests:
Global RV size and function [57][61]
- Best views: PSAX, A4CH
-
Normal findings
- RV ∼ 60% of LV size [57]
- Ventricular walls contract symmetrically.
- LV appears round on PSAX (septal wall not flattened by RV).
-
Abnormal findings
- Enlarged RV (RV volume ≥ LV volume)
- Acute: suggests pulmonary embolism or LV dysfunction with fluid overload
- Chronic: suggests pulmonary hypertension and/or chronic lung disease
- Hypokinesis
- D-sign (bowed or flattened LV septum): typically indicates acute RV strain
- RV wall hypertrophy ± RA enlargement: typically indicates chronic disease, e.g., COPD, pulmonary hypertension
- Enlarged RV (RV volume ≥ LV volume)
RV dilation and septal flattening in patients with acute hypotension and/or chest pain should raise concern for pulmonary embolism; further workup, including complete echocardiography, should be obtained urgently. [52]
Volume status [52][58]
- Best view: SIVC
- Findings: See “IVC ultrasound.”
Pericardial effusion and cardiac tamponade [57][62]
- Best views
-
Normal findings
- No or small anechoic space between the myocardium and pericardium
- Anechoic space is seen only in systole.
- The RA remains open during systole and the RV remains open during diastole.
-
Abnormal findings
-
Pericardial effusion
- Anechoic space between the myocardium and pericardium
- See “Ultrasound findings suggestive of pericardial effusion” for details.
-
Cardiac tamponade
- RA collapse in systole and/or RV collapse in diastole
- See “Echocardiographic findings suggestive of cardiac tamponade” for details.
-
Pericardial effusion
Gross cardiac abnormalities
- Severe regurgitant valve disorders
- Color Doppler imaging is added to A4CH, PLAX, and PSAX views. [58]
- Qualities of the regurgitant jet (e.g., area, volume) may be used for grading. [63][64]
- Ventricular hypertrophy
- Intracardiac mass
Condition-specific clinical applications
Lung POCUS![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
The basic lung ultrasound in emergency (BLUE) protocol is used in conjunction with the physical examination to rapidly narrow the differential diagnosis of respiratory failure. [67]
Indications [67]
- Dyspnea
- Tachypnea
- Increased work of breathing
- Chest trauma
- Ultrasound-guided procedure (e.g., thoracentesis)
Assessment goals
- Evaluation for the following causes of respiratory failure: [67]
- Pneumonia
- Congestive heart failure
- Pleural effusion
- Alveolar-interstitial syndrome
- Identification of the following complications of trauma: [68][69]
- Pneumothorax (large)
- Hemothorax [70]
- Pulmonary contusion
Technique [71]
Initial steps
- Patient position: supine or semirecumbent
- Transducer: 3–6 MHz curvilinear probe (preferred), 5–10 MHz linear transducer
- Initial probe orientation: perpendicular to ribs
- Depth: 12–18 cm
- Filters: off
Landmarks [71]
-
Upper BLUE point
- Location: anterior chest between the clavicle and 4th rib
- Utility: identification of pneumothorax and pulmonary edema
-
Lower BLUE point
- Location: anterior chest below the 4th rib
- Utility: identification of pneumothorax and pulmonary edema
-
Posterolateral alveolar and/or pleural syndrome (PLAPS) point
- Location: posterior axillary line at the level of the lower BLUE point
- Utility: identification of lung consolidation and pleural effusion
Sequence
- Perform the following steps at the upper and lower BLUE points bilaterally:
- Identify the pleural line.
- Look for lung sliding.
- Look for lung point.
- Evaluate the aeration of the lung tissue.
- Evaluate for the following at each PLAPS point:
- Lung consolidation (e.g., Shred sign, tissue-like sign)
- Pleural effusion
Findings [70][72]
These are the basic signs used to distinguish normal lung tissue from a pathological condition.
-
Pleural line (Bat sign)
- A hyperechoic line extending between the ribs distal to the intercostal muscles
- Normal finding of the visceral and parietal pleural interface
- Best seen with the probe in a longitudinal position across two ribs
-
Lung sliding: a normal finding during respiration showing back-and-forth sliding of the visceral and parietal pleura within the pleural line
-
Seashore sign: normal finding seen in M-mode during respiration
- Proximal to pleural line: Stationary parietal pleura and chest wall appear as horizontal lines (“waves”).
- Distal to pleural line: Moving visceral pleura appears granular (“sand”).
-
Stratosphere sign: abnormal finding seen in M-mode
- Horizontal lines are seen throughout the entire field; the granular pattern from moving visceral pleura is absent.
- Seen in the absence of lung sliding, e.g., pneumothorax
-
Seashore sign: normal finding seen in M-mode during respiration
-
Pulmonary A-lines
- Hyperechoic lines parallel to and at equal intervals below the pleural line
- Line intensity fades with increasing distance from the probe.
- Normal finding caused by reverberation of aerated lung tissue
-
Pulmonary B-lines
- Hyperechoic vertical lines arising perpendicular to the pleural line
- Move with respiration, do not fade with depth, and obscure pulmonary A-lines
- ≥ 3 lines indicate increased tissue density, e.g., pulmonary edema, atelectasis.
- Correlate with Kerley B lines on chest x-ray
-
Quad sign (sinusoid sign)
- Parallel horizontal hyperechoic lines between the vertical hyperechoic lines of adjoining rib cortices
- M-mode: A sinusoid pattern is seen as the distance between the parietal and visceral pleura varies with respiration.
- Caused by fluid separating the visceral and parietal pleura
- Indicates pleural effusion
-
Shred sign (fractal sign) and tissue-like sign
- Ragged or irregular hyperechoic line distal to the pleural line
- Tissue distal to the shred sign is dense and appears similar to hepatic tissue.
- Sensitive indicator of lung consolidation, e.g., in pneumonia, pulmonary contusion, alveolar-interstitial syndrome
-
Lung point
- Visible lung sliding adjacent to an area without visible lung sliding
- M-mode: appears as alternating seashore and stratosphere signs
- Pathognomonic for pneumothorax but not always seen, especially in large pneumothorax
-
Pleural effusion findings
- Hypoechoic or anechoic spaces in the lower margins of the pleural cavity
- See “Ultrasound findings suggestive of pleural effusion” for details.
Interpretation [70]
-
Rapid rules of thumb
- No lung sliding and/or visible lung point: pneumothorax
- Lung sliding with multiple pulmonary B-lines: pulmonary edema
- Lung sliding with pulmonary A-lines: COPD or asthma exacerbation, pulmonary embolism
- Signs of consolidation ± lung sliding: pneumonia
- Hypoechoic or anechoic space in the lower margins of the pleural cavity and/or quad sign: pleural effusion, hemothorax
-
Detailed condition-specific findings
- See “Thoracic ultrasound for pleural effusion.”
- See “POCUS in acute heart failure.”
- See “POCUS for VTE.”
- See “POCUS for pneumothorax.”
Consider adding POCUS for DVT and FoCUS in patients with dyspnea and a normal lung POCUS to assess for pulmonary embolism. [70]
Deep vein thrombosis![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
- Indication: suspected DVT if formal lower extremity venous ultrasound cannot be promptly obtained [73]
- Patient position: supine; leg rotated laterally at the hip and knee bent at ∼ 30º [74]
- Probe: linear [74]
-
Landmarks
-
Veins
- Common femoral vein (CFV)
- Great saphenous vein (GSV)
- Deep femoral vein (DFV)
- Femoral vein (FV)
- Popliteal vein (PV)
-
Arteries
- Common femoral artery (CFA)
- Femoral artery (FA)
- Popliteal artery (PA)
-
Veins
-
Technique [74]
- Compression technique: Holding the probe perpendicular to the skin, apply enough downward pressure to slightly compress the pulsatile artery.
- 3-point protocol steps
- Locate the CFV and CFA at the branch point of the GSV from the CFV and apply compression.
- Move the transducer distally along the CFV just past the branch point of the FV and DFV where the FA is superficial to the FV, and apply compression.
- Reposition the probe behind the knee and locate the PV superficial to the PA and apply compression.
-
Interpretation [74]
- Normal: The pressure needed to slightly compress the artery should completely collapse a nonthrombosed vein.
- Abnormal
- A noncollapsible vein is highly suggestive of DVT.
- Direct visualization of an intraluminal hyperechoic mass confirms the diagnosis.
- See “Supportive ultrasound findings of DVT” for details.
Additional POCUS examinations![toggle arrow icon](https://manus-media.amboss.com/icons/chevron_up.svg)
Genitourinary POCUS [75][76]
Bladder POCUS [75]
- Indication: suspected urinary retention
- Patient position: supine
- Probe: 2–5 MHz curvilinear probe
-
Technique
- Place the probe in the midline above the pubic symphysis.
- Identify the bladder (an anechoic space surrounded by hyperechoic walls).
- Measure the bladder dimensions in sagittal and transverse planes between the inner walls.
- Calculate bladder volume: 0.52 × depth × width × height.
-
Findings
- Postvoid residual > 50 mL (or > 100 mL in patients aged > 65 years) indicates urinary retention. [77]
- Incidental findings: UVJ or bladder stones, free fluid outside of the bladder wall
Renal POCUS [75][76]
- Indication: renal colic
- Patient position: supine or lateral decubitus
- Probe: 2–5 MHz curvilinear probe
-
Technique
- Orient the probe longitudinally (cephalad to caudal orientation) with the indicator toward the head.
- Place the probe in the midaxillary line.
- Right side: Begin at the 10th or 11th intercostal space.
- Left side: Begin at the 8th to 10th intercostal space.
- Rotate and/or fan the probe to obtain the best view.
-
Findings
- Dilation of the collecting system [78]
- Mild hydronephrosis: dilation of the renal pelvis and/or major calyces
- Moderate hydronephrosis: dilation includes minor calyces
- Severe hydronephrosis: dilation accompanied by parenchymal thinning
- Hyperechoic and/or twinkling objects that cast shadows indicate renal calculi.
- Dilation of the collecting system [78]
Bowel POCUS [79][80]
-
Indication
- Abdominal pain
- Abdominal distension
- Ultrasound-guided procedure (e.g., paracentesis)
- Patient position: supine
- Probe: linear phased array or curvilinear probe [79]
-
Technique
- Examine the entire abdomen systematically. [80]
- Scan the RUQ for air. [79]
- Evaluate the Morison pouch, perisplenic space, and the pelvis for free intraperitoneal fluid.
- Locate the site of obstruction after the global examination is complete.
- See also “FAST.”
-
Findings
- Thickened peritoneal stripe and reverberation artifacts: free intraperitoneal air
- Large anechoic or hypoechoic spaces: free intraperitoneal fluid
- Dilated small bowel (> 2.5 cm), thickened bowel wall (> 3 mm), or abnormal peristalsis: small bowel obstruction
- Visualization of the plicae circulares (keyboard sign): small bowel obstruction
- Noncompressible appendix > 6 mm in diameter: acute appendicitis
Soft tissue and musculoskeletal POCUS [81][82]
-
Indication
- Suspected injury or infection
- Ultrasound-guided procedure (e.g., abscess incision and drainage, arthrocentesis)
- Probe: 7–12 MHz linear array probe for superficial structures, low-frequency curvilinear probe for deep structures
-
Technique
- Begin the examination a short distance from the injury to visualize normal anatomy.
- Slowly slide the probe into the area of interest and obtain both longitudinal and transverse images.
- Consider comparing to the unaffected contralateral limb.
-
Findings
- Cellulitis: increased echogenicity and cobblestone appearance of subcutaneous tissue
-
Abscess
- An isoechoic or hypoechoic circular area surrounded by a hyperechoic ring
- Posterior acoustic enhancement [83]
- Compression of the skin with the probe causes movement of the contents in the hypoechoic area (Squish sign).
- Foreign body
- Reverberation artifacts from smooth items, e.g., metal
- Acoustic shadow from irregular items, e.g., wood splinter
- Hypoechoic halo around the object (inflammatory response if the foreign body has been present for > 24 hours)
- Necrotizing fascitis
- Subcutaneous thickening
- Hypoechoic collections (caused by fluid)
- Highly echogenic areas with posterior shadowing (caused by gas)
- Joint effusions: anechoic fluid collection within the joint
Ocular POCUS [84][85]
- Indications
- Probe: 7–14 MHz linear array probe
-
Technique
- Maneuver the patient into the supine or head-up position.
- Consider placing Tegaderm over the closed eyelid.
- Apply a large quantity of gel over the Tegaderm or closed eyelid.
- Place the probe in the gel but do not apply pressure to the globe.
- Steady the hand by resting a finger against the nose or temple.
- Obtain transverse and/or sagittal images.
- Instruct the patient to move the eye to help visualize the whole globe and/or differentiate artifacts from pathological findings.
-
Findings and possible causes
- Echogenic material in the globe: foreign body
- Anechoic fluid behind the eye and distortion of the globe: retrobulbar hematoma
- Cloudy, hyperechoic posterior chamber: vitreous hemorrhage
- Lens in the anterior or posterior chamber: lens dislocation
- Mobile, hyperechoic band anterior to the choroid: retinal detachment
- Decreased globe size, anterior chamber collapse, and/or haziness of the posterior chamber: ruptured globe
Do not perform ocular POCUS if an open globe injury is suspected; stop the examination immediately if a foreign body or features of a ruptured globe are seen. [84]