# 01 - 493 Point-of-Care Ultrasound

## 493 Point-of-Care Ultrasound

Emerging Topics in Clinical Medicine
PART 20
Wilma Chan, Nilam J. Soni, Paul H. Mayo

Point-of-Care Ultrasound
DEFINITION
Point-of-care ultrasound (POCUS) is defined as the acquisition, 
interpretation, and clinical integration of ultrasonographic views by a 
treating clinician in real time at the patient’s bedside. POCUS is distinct 
from consultative ultrasound where a clinician orders an ultrasound 
exam, a sonographer acquires a comprehensive set of images, an imag­
ing specialist (most often a radiologist or cardiologist) interprets the 
images, and the ordering clinician receives an ultrasound report and 
integrates findings into clinical decision-making (Fig. 493-1). The 
goal of POCUS is not to replace the imaging specialist or the highresolution data provided by computed tomography (CT) or magnetic 
resonance imaging (MRI), but rather to improve diagnostic and thera­
peutic decisions made by the treating clinician at the bedside.
POCUS became part of trauma care in emergency departments 
in the 1980s, and subsequently, many specialties began incorporat­
ing POCUS into patient care. The 1999 House of Delegates from the 
American Medical Association passed a resolution (AMA HR. 802) 
enabling each specialty to define its own scope and appropriate use of 
POCUS. Specialty-based guidelines emerged supporting credentialing 
processes and defining standard scanning protocols to answer focused 
diagnostic questions. Common clinical scenarios, such as acute dys­
pnea, abdominal pain, and shock, can be rapidly characterized using 
POCUS (Table 493-1).
In internal medicine, there has been expanding interest in POCUS 
since the 2000s. POCUS can enhance diagnostic accuracy, treatment, 
monitoring, and screening of patients, as well as improve patient and 
clinician confidence and procedural safety (Fig. 493-2).
Physical
Examination
Point-of-Care
Consultative
Ultrasound
Ultrasound
ask
select
acquire
interpret
act
Bedside Clinician
Sonographer
Radiologist or Cardiologist
FIGURE 493-1  Workflow schematic comparing point-of-care ultrasound to physical 
examination and consultative ultrasound. Medical decision-making begins with 
asking a targeted question, selecting the diagnostic modalities, acquiring and 
interpreting images or other data, and ultimately, acting to incorporate the new 
findings into the patient’s care. The three different shapes represent various 
personnel in this process, and curved arrows demonstrate the exchange of 
information among providers across different stages. (Reproduced with permission 
from NJ Soni, BP Lucas: Diagnostic point-of-care ultrasound for hospitalists. J Hosp 
Med 10, 2014.)

Portable ultrasound machines are categorized as cart-based 
machines versus handheld devices with wired or wireless probes con­
nected to a tablet or mobile phone. Linear, curvilinear, and phasedarray probes are commonly available, and multifunctional probes are 
emerging. Linear high-frequency probes have excellent image resolu­
tion but limited penetration, so they are used primarily to examine 
superficial structures. Deeper structures are visualized with curvilinear 
or phased-array probes, which have a lower frequency. Portable ultra­
sound devices offer two-dimensional or gray-scale imaging, and color 
flow and spectral Doppler imaging. Important considerations when 
purchasing an ultrasound machine include portability, image resolu­
tion, screen size, probe types, imaging modes, battery life, disinfection, 
image archiving capability, and warranty.
COMMON APPLICATIONS
■
■CARDIAC
In the 1990s, clinicians began to perform focused cardiac POCUS 
exams to guide immediate management, especially for urgent and 
life-threatening conditions. In intensive care units and emergency 
departments, cardiac POCUS is routinely used to rapidly categorize 
shock states and acute respiratory failure. In outpatient settings, it is 
often used for serial monitoring of stable patients with chronic forms 
of heart disease.
A limited or focused cardiac POCUS exam includes five core views: 
parasternal long-axis, parasternal short-axis (mid-ventricular or papil­
lary muscle level), apical four-chamber, subcostal four-chamber, and 
inferior vena cava views. Clinicians with comprehensive training in 
echocardiography, including cardiologists and intensivists certified 
by the National Board of Echocardiography, may perform advanced 
Doppler measurements of cardiac pressures and function. Cardiac 
POCUS and consultative echocardiography are complementary tech­
niques where the clinical situation and operator skill determine which 
approach is most appropriate.
Cardiac POCUS exams can guide immediate and ongoing clinical 
decision-making when performed serially. To categorize shock states, 
left ventricular systolic function can be qualitatively categorized as nor­
mal (Video 493-1), hyperdynamic (Video 493-2), moderately reduced 
(Video 493-3), or severely reduced (Video 493-4). Other findings 
detected by cardiac POCUS that can change immediate management 
include acute right ventricular failure (Video 493-5), cardiac tampon­
ade (Video 493-6), and gross valvular abnormalities, including severe 
regurgitation of the tricuspid (Video 493-7), mitral (Video 493-8), 
and aortic (Video 493-9) valves, as well as large valvular vegetations 
(Video 493-10).
Competence in basic cardiac POCUS has become a mandatory 
component of an increasing number of specialties, including emer­
gency medicine, pulmonary medicine, critical care medicine, and 
anesthesiology.
■
■LUNG AND PLEURA
Historically, thoracic ultrasonography, comprised of lung and pleural 
ultrasound, was established by clinicians specialized in critical care, 
pulmonary, and emergency medicine. The pleural surface can be 
imaged through the intercostal spaces using high-frequency probes, 
while low-frequency probes penetrate deeper, allowing visualization 
of structures in the thorax. Ultrasound is superior to chest x-ray for 
detection of pneumothorax, early interstitial processes, and small pleu­
ral effusions and is superior to chest CT for characterization of early 
complex pleural effusions.
Pleural fluid is seen as a relatively hypoechoic space bounded by 
the diaphragm, chest wall, and atelectatic lung (Video 493-11). Pleural 
effusions are quantified as small (Video 493-12), moderate (Video 
493-13), or large (Video 493-14), and qualitatively assessed as simple, 
homogeneously echogenic, complex nonseptated (Video 493-15), or 
complex septated (Video 493-16). Ultrasound guidance to identify an

Pleural effusion
Dullness to percussion

4.8
0.1
Visualization of pleural fluid

0.07
Pulmonary edema
Crackles
19–64
82–94
3.4
NS
Bilateral B-lines

10.4
0.06
Pneumonia
Bronchial breath sounds

3.3
NS
Consolidation pattern
94–95
90–96
13.5
0.06
Elevated CVP (>8 cmH20)
Neck vein inspection
47–92
93–96
9.7
0.3
CVP >10 mmHg (IVC size >2 cm)

4.9
0.32
Reduced ejection fraction
3rd heart sound (S3)
11–51
85–98
3.4
0.7
LV systolic dysfunction
84–91
85–88
6.5
0.14
 
FINDING
SENSITIVITY (%)
SPECIFICITY (%)
LR+
LR–
FINDING
SENSITIVITY (%)
SPECIFICITY (%)
LR+
LR–
Elevated LV pressure
4th heart sound (S4)
37–71
50–70
NS
NS
PCWP 17 if IVC >2.0

4.4
0.3
Pulmonary
 
 
 
 
 
 
 
 
 
 
Cardiac
 
 
 
 
 
 
 
 
 
 
PATHOLOGY
PHYSICAL EXAMINATION
POINT-OF-CARE ULTRASOUND
PART 20
Emerging Topics in Clinical Medicine
TABLE 493-1  Comparison of Physical Examination Versus Point-of-Care Ultrasound Findings for Common Pathologies
Egophony
4–16
96–99
4.1
NS
Decreased breath sounds

5.2
0.1
Crackles
19–67
36–94
1.8
0.8

Congestive heart failure
Rales
12–23
88–96
NS
NS
Bilateral B-lines

19.4
0.03
Abdominojugular test
55–84
83–98
8.0
0.3
CVP >10 mmHg (IVC size >2 cm)

4.9
0.32
Ascites
Bulging flanks
73–93
44–70
1.9
0.4
Visualized ascites

0.04
Urinary retention (>400 mL)
Palpation

1.9
0.3
Bladder volume (>600 mL)

3.84
0.05
Lower extremity DVT
Calf swelling >2 cm
61–67
69–71
2.1
0.5
Compression venous ultrasonography

0.04
Abbreviations: CVP, central venous pressure; DVT, deep-venous thrombosis; IVC, inferior vena cava; JVP, jugular venous pulse; LE, lower extremity; LR, likelihood ratio; LV, left ventricle or left ventricular; NA, not applicable; NS, not 
Abdomen
 
 
 
 
 
 
 
 
 
 
Source: Reproduced with permission from A Bhagra et al: Point-of-care ultrasonography for primary care physicians and general internists. Mayo Clin Proc 91:1811, 2016.
probability)
38–87
71–99
6.3
NA
Elevated JVP
10–58
96–97
3.9
NS
LE edema

93–96
NS
NS
Homan’s sign
10–54
39–89
NS
NS
Flank dullness
80–94
29–69
NS
0.3
Shifting dullness
60–87
56–90
2.3
0.4
Fluid wave
50–80
82–92
5.0
0.5
significant; PCWP, pulmonary capillary wedge pressure.
Wells’ score (high 
Soft Tissue and Musculoskeletal

History &
Physical Exam
diagnostic
procedure
POCUS
diagnose
Consultative
imaging
Diagnosis
Labs
therapeutic
procedure
Treatment
treat
POCUS
POCUS
monitor
No improvement
Improvement
POCUS
screen
Follow-up
FIGURE 493-2  Clinicians can use point-of-care ultrasound (POCUS) as part of a 
patient’s diagnosis, treatment, monitoring, and screening. A patient encounter 
begins with the history and physical examination, followed by a focused bedside 
ultrasound exam to narrow the differential diagnosis and guide workup. Treatment 
plans can include bedside procedures that are performed with ultrasound guidance. 
Serial POCUS exams can monitor disease processes and guide ongoing treatment 
decisions. Screening POCUS exams can detect asymptomatic, potentially treatable 
conditions. (Reproduced with permission from NJ Soni, BP Lucas: Diagnostic pointof-care ultrasound for hospitalists. J Hosp Med 10:120, 2015.)
optimal site for pleural drainage reduces the risk of pneumothorax and 
bleeding complications.
Normal air-filled lung tissue reflects sound waves, thereby pre­
venting visualization of aerated lung parenchyma. Two hallmarks of 
normal aeration of lung on ultrasound include lung sliding (Video 
493-17), which results from respirophasic movement of the parietal 
and visceral pleural interface, and A-lines, which are horizontally ori­
entated reverberation artifacts seen deep to the pleural line of air-filled 
lungs (Video 493-18). Interstitial abnormalities manifest as B-lines, 
which are vertically orientated hyperechoic lines emanating from the 
pleural line to the bottom of the screen (Video 493-19). Depending 
on their density and distribution, B-lines can support a diagnosis of 
cardiogenic pulmonary edema, pneumonitis, acute respiratory distress 
syndrome, or interstitial lung diseases. Consolidation results in lung 
that is tissue dense on ultrasound. Mobile air bronchograms and blood 
flow detected by color flow Doppler are associated with pneumonia 
when seen in an area of consolidation (Video 493-20). Similar to chest 
x-ray and chest CT, identification of consolidation by lung ultrasound 
does not specify a diagnosis of pneumonia, and clinical correlation is 
required.
■
■ABDOMEN
Evaluation of peritoneal free fluid is a common abdominal POCUS 
application. POCUS cannot specify the type of fluid (i.e., ascites, blood, 
urine, bile, chyme) but can detect as little as 100–500 mL of peritoneal 
free fluid. When ascites is present (Video 493-21), POCUS can identify 
a safe site for paracentesis, improving procedural success and compli­
cation rates compared to landmark-based techniques. POCUS elimi­
nates attempts at paracentesis when an insufficient volume of ascites 
is present (Video 493-22). The best site, depth, and angle for needle 
insertion is determined using the ultrasound probe followed by color 
flow Doppler examination of the proposed trajectory of needle inser­
tion to avoid injury to abdominal wall blood vessels (Video 493-23).
POCUS is used in the initial evaluation of acute renal failure and 
decreased urine output. Bladder ultrasound can rapidly identify 
presence or absence of urine in the bladder and confirm appropriate 
placement and function of a urinary catheter (Videos 493-24 and 
493-25). Bladder ultrasound is more reliable than automated bladder 

scanners for urinary retention, as bladder scanners can falsely report 
pelvic free fluid (i.e., ascites, cysts, small bowel obstruction) as elevated 
bladder volume. POCUS is effective to evaluate kidney size and echo­
genicity; identify renal cysts, large stones, and masses; and detect and 
grade hydronephrosis (Videos 493-26 to 493-28), thereby identifying 
obstructive uropathy.

POCUS can diagnose an abdominal aortic aneurysm (AAA) with 
high sensitivity and specificity (Videos 493-29 and 493-30). A pro­
tocol that emphasizes complete visualization of the abdominal aorta 
from celiac trunk through the iliac bifurcation in both transverse 
and longitudinal planes can provide a reliable evaluation of the aorta. 
POCUS use for AAA screening may reduce morbidity and mortality 
among high-risk patients.
POCUS has utility for evaluation of small-bowel function. Normally, 
the small bowel is partially filled with air that obscures visualization 
due to scattering of sound waves. When a small-bowel obstruction 
(SBO) develops, the air-filled loops of bowel become fluid-filled, per­
mitting visualization of the bowel walls. Diagnostic criteria for SBO 
by ultrasound include dilation of the bowel (diameter >2.5 cm), fluidfilled small-bowel loops (confirmed by appearance of plicae circularis 
at the perimeter), and hyperactive to-and-fro peristalsis within loops 
of small bowel (Video 493-31). Combining patient history, physical 
examination, and a systematic survey of all four quadrants by ultra­
sound, clinicians can diagnose SBO rapidly and reliably. For a new 
diagnosis of SBO, POCUS can expedite early intervention and surgical 
consultation. For recurrent SBO, POCUS can reduce repeat radiation 
exposure by CT scans and expedite initiation of medical management.
CHAPTER 493
■
■LOWER EXTREMITY DEEP-VEIN THROMBOSIS
Two-dimensional compression ultrasound is a rapid and accurate diag­
nostic technique for deep-vein thrombosis (DVT) that clinicians can 
learn after brief training programs. A point-of-care lower extremity com­
pression ultrasound exam yields similar diagnostic accuracy for detec­
tion of DVTs as traditional duplex or triplex ultrasound exams. DVTs 
commonly form at venous junctions because of high turbulence, and 
hence, compression ultrasound is performed at major branchpoints of 
the venous system. A perpendicular compression technique is required 
to ensure complete venous compression with wall-to-wall touching. A 
noncompressible vein is diagnostic of DVT (Video 493-32), and visual­
ization of intraluminal clot is not required to diagnose a DVT.
Point-of-Care Ultrasound
■
■SKIN AND SOFT TISSUE
POCUS allows rapid differentiation between skin and soft tissue infec­
tions (SSTIs) and reactive lymph nodes, seromas, hematomas, hernias, 
thrombophlebitis, DVT, cysts, and bursitis. For SSTIs, POCUS can 
reduce unnecessary attempts at incision and drainage and avoid delays 
in surgical intervention. SSTIs range from cellulitis to phlegmon, 
abscess, and necrotizing fasciitis. POCUS can accurately distinguish 
abscess from cellulitis, but diagnostic accuracy is more variable for 
necrotizing fasciitis. To diagnose cellulitis, POCUS identifies subcuta­
neous edema described as “cobblestoning” (Video 493-33). Abscesses 
appear as irregular, enclosed areas superficially with compressible 
material and absent central flow on color Doppler (Video 493-34).
■
■VASCULAR ACCESS
Current evidence supports use of ultrasound guidance for insertion of 
central venous catheters (CVCs) in the femoral, internal jugular, and 
axillary veins. Ultrasound guidance for insertion of internal jugular 
CVCs improves procedure success rates and reduces complications, 
particularly pneumothorax and arterial punctures. A preprocedure 
ultrasound survey identifies potential vessels to cannulate and can 
reveal unsuspected venous thrombosis, atypical anatomy, and venous 
stenosis. During insertion, real-time visualization of the needle tip 
reduces procedure attempts and needle redirections, which reduces 
the risk of complications. Sonographic confirmation of the guidewire 
in the target vein provides a safety check prior to venous dilation and 
insertion of the CVC.
For peripheral intravenous (PIV) catheter insertion, ultrasound 
can increase cannulation success rates while reducing puncture 
attempts, time to cannulation, and trauma to surrounding structures,

particularly in patients with anticipated difficult PIV placement or 
after failed attempts using standard techniques. Ultrasound identifies 
peripheral veins that are large, linear, and superficial, and real-time 
ultrasound guidance allows visualization of the needle tip entering the 
vessel lumen.

TRAINING
■
■PATHWAYS
Ultrasound training is a longitudinal process for clinicians as they 
progress through medical school, residency, and fellowship and enter 
clinical practice. Training recommendations for POCUS have been 
developed for different stages of medical education but with varying 
definitions of competence. Regardless of the clinical rank of the learner, 
competence in POCUS requires mastery of ultrasound knowledge 
(e.g., clinical indications, applications, limitations, artifacts), image 
acquisition, image interpretation, and clinical integration. Image acqui­
sition and interpretation skills are learned at varying rates and require 
deliberate practice.
■
■CERTIFICATION
Currently, there is no widely accepted certification for POCUS. Some 
residency and fellowship training programs, such as critical care and 
emergency medicine, require comprehensive training in POCUS, and 
hospitals generally grant POCUS privileges to physicians with board 
certification in these specialties. In contrast, internal medicine resi­
dency training does not require comprehensive POCUS training, and 
board certification in internal medicine does not imply competence 
in POCUS. Several internal medicine residency programs and profes­
sional societies have developed POCUS training courses.
PART 20
Emerging Topics in Clinical Medicine
■
■CREDENTIALING AND PRIVILEGES
Clinical privileges are governed by the rules and regulations of indi­
vidual hospitals. A hospital’s credentialing and privileging committee 
is responsible for developing criteria for granting privileges for POCUS 
use, which may be guided by specialty-specific guidelines. Some hos­
pitals will designate a local POCUS expert to assess competence in 
POCUS prior to granting privileges for POCUS use in patient care. 
Hospital credentialing and privileging bodies may designate POCUS 
as a core privilege of a specialty (e.g., emergency medicine privileges 
include POCUS use) or as add-on privileges separate from the primary 
specialty’s skills. Some well-established POCUS applications, such as 
ultrasound-guided CVC insertion, are commonly designated as core 
privileges when use of ultrasound guidance is standard of care. In 
contrast, less common POCUS applications, such as peripheral nerve 
blocks, may be designated as add-on privileges.
FUTURE DIRECTIONS
The increasing portability and affordability of ultrasound devices have 
allowed internal medicine clinicians to incorporate POCUS into front­
line patient care. Increasing POCUS use in internal medicine requires 
development of effective training programs during residency training 
and for internists in-practice. Tele-ultrasound has shown promise for 
training clinicians and delivering patient care remotely. In the coming 
years, artificial intelligence will facilitate both POCUS training and use 
in clinical care, and remote serial monitoring of common conditions 
like heart failure may be possible with patients’ use of POCUS.
■
■FURTHER READING
American College of Emergency Physicians Ultrasound 
Guidelines: Emergency, point-of-care, and clinical ultrasound 
guidelines in medicine. Available at: https://www.acep.org/siteassets/
new-pdfs/policy-statements/ultrasound-guidelines--emergency-pointof-care-and-clinical-ultrasound-guidelines-in-medicine.pdf. Accessed 
December 3, 2024.
Mayo PH et al: American College of Chest Physicians/La Societe de 
Reanimation de Langue Francaise statement on competence in criti­
cal care ultrasonography. Chest 135:1050, 2009.
Qaseem A et al: Appropriate use of point-of-care ultrasonography in 
patients with acute dyspnea in emergency department or inpatient 

settings: A clinical guideline from the American College of Physicians. 
Ann Intern Med 174:985, 2021.
Soni NJ et al: Point-of-care ultrasound for hospitalists: A position 
statement of the Society of Hospital Medicine. J Hosp Med 14:E1, 
2019.
Soni NJ, Arntfield R, Kory PD: Point-of-Care Ultrasound, 2nd ed. 
Philadelphia, Elsevier/Saunders, 2019.
Spencer KT et al: Focused cardiac ultrasound: recommendations from 
the American Society of Echocardiography. J Am Soc Echocardiogr 
26:567, 2013.
VIDEO 493-1  Normal cardiac function.
VIDEO 493-2  Hyperdynamic cardiac function.
VIDEO 493-3  Reduced cardiac function.
VIDEO 493-4  Severely reduced cardiac function.
VIDEO 493-5  Acute right heart failure.
VIDEO 493-6  Cardiac tamponade.
VIDEO 493-7  Tricuspid valve regurgitation.
VIDEO 493-8  Mitral valve regurgitation.
VIDEO 493-9  Aortic valve regurgitation.
VIDEO 493-10  Tricuspid valve vegetation.
VIDEO 493-11  Lung atelectasis.
VIDEO 493-12  Small pleural effusion.
VIDEO 493-13  Moderate pleural effusion.
VIDEO 493-14  Large pleural effusion.
VIDEO 493-15  Homogenous pleural effusion.
VIDEO 493-16  Loculated pleural effusion.
VIDEO 493-17  Pleural sliding.
VIDEO 493-18  A-Line artifact.
VIDEO 493-19  B-Line artifact.
VIDEO 493-20  Lung consolidation.
VIDEO 493-21  Large-volume ascites.
VIDEO 493-22  Small-volume ascites.
VIDEO 493-23  Abdominal wall vessels with color Doppler.
VIDEO 493-24  Urinary catheter balloon in empty bladder.
VIDEO 493-25  Malfunctioning urinary catheter.
VIDEO 493-26  Mild hydronephrosis.
VIDEO 493-27  Moderate hydronephrosis.
VIDEO 493-28  Severe hydronephrosis.
VIDEO 493-29  Abdominal aortic aneurysm.
VIDEO 493-30  Abdominal aortic aneurysm.
VIDEO 493-31  Small-bowel obstruction.
VIDEO 493-32  Deep-vein thrombosis.
VIDEO 493-33  Cellulitis.
VIDEO 493-34  Simple abscess.