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Point-of-Care Ultrasound

Chapter 493 | Part 20: Emerging Topics in Clinical Medicine · Parts 19-20 – Consultative & Emerging Topics

Detailed clinical reference synthesised from Harrison's Principles of Internal Medicine, 22nd Edition

🔑 Key Clinical Points

  1. 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.
  2. POCUS is distinct from consultative ultrasound where a sonographer acquires images and an imaging specialist interprets them.
  3. The goal of POCUS is to improve diagnostic and therapeutic decisions, not to replace high-resolution CT or MRI.
  4. Five core views for focused cardiac POCUS: parasternal long-axis, parasternal short-axis, apical four-chamber, subcostal four-chamber, and inferior vena cava.
  5. Lung ultrasound hallmarks: lung sliding, A-lines, and B-lines.
  6. A noncompressible vein is diagnostic of deep-vein thrombosis (DVT); visualization of intraluminal clot is not required.
  7. POCUS has high sensitivity and specificity for diagnosing abdominal aortic aneurysm (AAA).
  8. POCUS can detect as little as 100–500 mL of peritoneal free fluid.
  9. Training is a longitudinal process; currently, there is no widely accepted certification for POCUS.
  10. Credentialing is governed by hospital rules; some applications (e.g., CVC insertion) are core privileges, while others (e.g., nerve blocks) are add-on privileges.

📑 Table of Contents

📋 Figures in This Chapter

# Type Description
1 🖼 Figure Clinicians can use point-of-care ultrasound (POCUS) as part of a of patient’s...
2 🖼 Figure Workflow schematic comparing point-of-care ultrasound to physical examination and consultative ultrasound

1. DEFINITION & OVERVIEW

  • 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 imaging 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.
  • The goal of POCUS is not to replace the imaging specialist or the high-resolution data provided by computed tomography (CT) or magnetic resonance imaging (MRI), but rather to improve diagnostic and therapeutic decisions made by the treating clinician at the bedside.
  • Portable ultrasound machines are categorized as cart-based machines versus handheld devices with wired or wireless probes connected to a tablet or mobile phone.
  • Linear, curvilinear, and phased-array probes are commonly available, and multifunctional probes are emerging.
  • Linear high-frequency probes have excellent image resolution 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 ultrasound 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 resolution, screen size, probe types, imaging modes, battery life, disinfection, image archiving capability, and warranty.
  • POCUS became part of trauma care in emergency departments in the 1980s, and subsequently, many specialties began incorporating 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 dyspnea, abdominal pain, and shock, can be rapidly characterized using POCUS.
  • In internal medicine, there has been expanding interest in POCUS since the 2000s.
  • POCUS can enhance diagnostic accuracy, monitoring, and screening of patients, as well as improve patient and clinician confidence and procedural safety.

Table 1 — Table 493-1: Diagnostic Performance of POCUS vs Physical Examination vs Consultative Ultrasound

Condition POCUS Physical Examination Consultative Ultrasound
Pneumothorax Superior to chest x-ray Variable Superior to chest x-ray
Pleural Effusion Superior to chest x-ray Variable Superior to chest x-ray
Deep Vein Thrombosis (DVT) Similar to traditional duplex Variable Similar to traditional duplex
Abdominal Aortic Aneurysm (AAA) High sensitivity and specificity Variable High sensitivity and specificity
Small-Bowel Obstruction (SBO) Rapid and reliable Variable Rapid and reliable
Cellulitis Identifies subcutaneous edema Variable Identifies subcutaneous edema
Abscess Accurately distinguishes from cellulitis Variable Accurately distinguishes from cellulitis
Ascites Detects 100–500 mL Variable Detects 100–500 mL
Urinary Retention More reliable than automated scanners Variable More reliable than automated scanners
Hydronephrosis Detects and grades Variable Detects and grades

1.1 Cardiac POCUS

  • 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 papillary 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 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 normal, hyperdynamic, moderately reduced, or severely reduced.
  • Other findings detected by cardiac POCUS that can change immediate management include acute right ventricular failure, cardiac tamponade, and gross valvular abnormalities, including severe regurgitation of the tricuspid, mitral, and aortic valves, as well as large valvular vegetations.
  • Competence in basic cardiac POCUS has become a mandatory component of an increasing number of specialties, including emergency medicine, pulmonary medicine, critical care medicine, and anesthesiology.

1.2 Lung and Pleura POCUS

  • 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 pleural 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.
  • Pleural effusions are quantified as small, moderate, or large, and qualitatively assessed as simple, homogeneously echogenic, complex nonseptated, or complex septated.
  • Normal air-filled lung tissue reflects sound waves, thereby preventing visualization of aerated lung parenchyma.
  • Two hallmarks of normal aeration of lung on ultrasound include lung sliding, which results from respirophasic movement of the parietal and visceral pleural interface, and A-lines, which are horizontally oriented reverberation artifacts seen deep to the pleural line of air-filled lungs.
  • Interstitial abnormalities manifest as B-lines, which are vertically oriented hyperechoic lines emanating from the pleural line to the bottom of the screen.
  • 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.
  • 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.

1.3 Abdomen POCUS

  • 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, POCUS can identify a safe site for paracentesis, improving procedural success and complication rates compared to landmark-based techniques.
  • POCUS eliminates attempts at paracentesis when an insufficient volume of ascites is present.
  • 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 insertion to avoid injury to abdominal wall blood vessels.
  • POCUS is used in the initial evaluation of acute renal failure and in the 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.
  • 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 echogenicity; identify renal cysts, large stones, and masses; and detect and grade hydronephrosis, thereby identifying obstructive uropathy.
  • POCUS can diagnose an abdominal aortic aneurysm (AAA) with high sensitivity and specificity.
  • A protocol 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, permitting visualization of the bowel walls.
  • Diagnostic criteria for SBO by ultrasound include dilation of the bowel (diameter >2.5 cm), fluid-filled small-bowel loops (confirmed by appearance of plicae circularis at the perimeter), and hyperactive to-and-fro peristalsis within loops of small bowel.
  • Combining patient history, physical examination, and a systematic survey of all four quadrants by ultrasound, 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.

1.4 Lower Extremity and Vascular POCUS

  • Two-dimensional compression ultrasound is a rapid and accurate diagnostic technique for deep-vein thrombosis (DVT) that clinicians can learn after brief training programs.
  • A point-of-care lower extremity compression ultrasound exam yields similar diagnostic accuracy for detection 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, and visualization of intraluminal clot is not required to diagnose a DVT.
  • POCUS allows rapid differentiation between skin and soft tissue infections (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 subcutaneous edema described as 'cobblestoning'.
  • Abscesses appear as irregular, enclosed areas superficially with compressible material and absent central flow on color Doppler.
  • 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 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.

1.5 Skin and Soft Tissue POCUS

  • POCUS allows rapid differentiation between skin and soft tissue infections (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 subcutaneous edema described as 'cobblestoning'.
  • Abscesses appear as irregular, enclosed areas superficially with compressible material and absent central flow on color Doppler.

2. EPIDEMIOLOGY

  • POCUS became part of trauma care in emergency departments in the 1980s.
  • Subsequently, many specialties began incorporating 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.
  • In internal medicine, there has been expanding interest in POCUS since the 2000s.
  • POCUS can enhance diagnostic accuracy, monitoring, and screening of patients, as well as improve patient and clinician confidence and procedural safety.
  • Increasing POCUS use in internal medicine requires development of effective training programs during residency training and for internists in-practice.

3. ETIOLOGY & PATHOPHYSIOLOGY

  • POCUS is a technique rather than a disease process; therefore, etiology and pathophysiology are not applicable.
  • The chapter focuses on technical principles, probe types, and clinical applications.

4. CLINICAL FEATURES

  • POCUS can enhance diagnostic accuracy, treatment, monitoring, and screening of patients.
  • POCUS can improve patient and clinician confidence and procedural safety.
  • Cardiac POCUS findings include acute right ventricular failure, cardiac tamponade, and gross valvular abnormalities.
  • Lung POCUS findings include lung sliding, A-lines, B-lines, and consolidation.
  • Abdominal POCUS findings include ascites, AAA, SBO, and urinary retention.
  • Vascular POCUS findings include DVT and vascular access guidance.
  • Skin and Soft Tissue POCUS findings include cellulitis, abscess, and necrotizing fasciitis.

5. DIFFERENTIAL DIAGNOSIS

  • POCUS is used to narrow the differential diagnosis and guide workup.
  • 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.

6. INVESTIGATIONS & DIAGNOSIS

  • POCUS procedure diagnosis involves acquisition, interpretation, and clinical integration of ultrasonographic views.
  • Cardiac POCUS: Five core views (parasternal long-axis, parasternal short-axis, apical four-chamber, subcostal four-chamber, inferior vena cava).
  • Lung POCUS: Lung sliding, A-lines, B-lines, consolidation, pleural effusion quantification.
  • Abdominal POCUS: Ascites detection (100–500 mL), AAA visualization, SBO criteria (dilation >2.5 cm, fluid-filled loops, hyperactive peristalsis), urinary retention.
  • Vascular POCUS: DVT diagnosis (noncompressible vein), vascular access guidance.
  • Skin/Soft Tissue POCUS: Cellulitis (cobblestoning), abscess (irregular, enclosed areas, absent central flow).
  • Table 493-1 summarizes diagnostic performance of POCUS vs Physical Examination vs Consultative Ultrasound.

Table 2 — Table 493-1: Diagnostic Performance of POCUS vs Physical Examination vs Consultative Ultrasound

Condition POCUS Physical Examination Consultative Ultrasound
Pneumothorax Superior to chest x-ray Variable Superior to chest x-ray
Pleural Effusion Superior to chest x-ray Variable Superior to chest x-ray
Deep Vein Thrombosis (DVT) Similar to traditional duplex Variable Similar to traditional duplex
Abdominal Aortic Aneurysm (AAA) High sensitivity and specificity Variable High sensitivity and specificity
Small-Bowel Obstruction (SBO) Rapid and reliable Variable Rapid and reliable
Cellulitis Identifies subcutaneous edema Variable Identifies subcutaneous edema
Abscess Accurately distinguishes from cellulitis Variable Accurately distinguishes from cellulitis
Ascites Detects 100–500 mL Variable Detects 100–500 mL
Urinary Retention More reliable than automated scanners Variable More reliable than automated scanners
Hydronephrosis Detects and grades Variable Detects and grades

6.1 Cardiac Investigations

  • A limited or focused cardiac POCUS exam includes five core views: parasternal long-axis, parasternal short-axis (mid-ventricular or papillary muscle level), apical four-chamber, subcostal four-chamber, and inferior vena cava views.
  • 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 normal, hyperdynamic, moderately reduced, or severely reduced.
  • Other findings detected by cardiac POCUS that can change immediate management include acute right ventricular failure, cardiac tamponade, and gross valvular abnormalities, including severe regurgitation of the tricuspid, mitral, and aortic valves, as well as large valvular vegetations.

6.2 Lung and Pleura Investigations

  • Normal air-filled lung tissue reflects sound waves, thereby preventing visualization of aerated lung parenchyma.
  • Two hallmarks of normal aeration of lung on ultrasound include lung sliding, which results from respirophasic movement of the parietal and visceral pleural interface, and A-lines, which are horizontally oriented reverberation artifacts seen deep to the pleural line of air-filled lungs.
  • Interstitial abnormalities manifest as B-lines, which are vertically oriented hyperechoic lines emanating from the pleural line to the bottom of the screen.
  • 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.
  • 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.
  • Pleural fluid is seen as a relatively hypoechoic space bounded by the diaphragm, chest wall, and atelectatic lung.
  • Pleural effusions are quantified as small, moderate, or large, and qualitatively assessed as simple, homogeneously echogenic, complex nonseptated, or complex septated.

6.3 Abdominal Investigations

  • 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, POCUS can identify a safe site for paracentesis, improving procedural success and complication rates compared to landmark-based techniques.
  • POCUS eliminates attempts at paracentesis when an insufficient volume of ascites is present.
  • 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 insertion to avoid injury to abdominal wall blood vessels.
  • POCUS is used in the initial evaluation of acute renal failure and in the 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.
  • 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 echogenicity; identify renal cysts, large stones, and masses; and detect and grade hydronephrosis, thereby identifying obstructive uropathy.
  • POCUS can diagnose an abdominal aortic aneurysm (AAA) with high sensitivity and specificity.
  • A protocol 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, permitting visualization of the bowel walls.
  • Diagnostic criteria for SBO by ultrasound include dilation of the bowel (diameter >2.5 cm), fluid-filled small-bowel loops (confirmed by appearance of plicae circularis at the perimeter), and hyperactive to-and-fro peristalsis within loops of small bowel.
  • Combining patient history, physical examination, and a systematic survey of all four quadrants by ultrasound, 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.

6.4 Vascular and Soft Tissue Investigations

  • Two-dimensional compression ultrasound is a rapid and accurate diagnostic technique for deep-vein thrombosis (DVT) that clinicians can learn after brief training programs.
  • A point-of-care lower extremity compression ultrasound exam yields similar diagnostic accuracy for detection 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, and visualization of intraluminal clot is not required to diagnose a DVT.
  • POCUS allows rapid differentiation between skin and soft tissue infections (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 subcutaneous edema described as 'cobblestoning'.
  • Abscesses appear as irregular, enclosed areas superficially with compressible material and absent central flow on color Doppler.

7. MANAGEMENT & TREATMENT

  • POCUS therapeutic procedure involves bedside procedures that are performed with ultrasound guidance.
  • POCUS use for AAA screening may reduce morbidity and mortality among high-risk patients.
  • POCUS can guide immediate and ongoing clinical decision-making when performed serially.
  • 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 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.
  • POCUS can identify a safe site for paracentesis, improving procedural success and complication rates compared to landmark-based techniques.
  • POCUS eliminates attempts at paracentesis when an insufficient volume of ascites is present.
  • 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 insertion to avoid injury to abdominal wall blood vessels.

7.1 Procedural Guidance

  • 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 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.
  • POCUS can identify a safe site for paracentesis, improving procedural success and complication rates compared to landmark-based techniques.
  • POCUS eliminates attempts at paracentesis when an insufficient volume of ascites is present.
  • 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 insertion to avoid injury to abdominal wall blood vessels.

7.2 Monitoring and Screening

  • Serial POCUS exams can monitor disease processes and guide ongoing treatment decisions.
  • Screening POCUS exams can detect asymptomatic, potentially treatable conditions.
  • Cardiac POCUS exams can guide immediate and ongoing clinical decision-making when performed serially.
  • In outpatient settings, cardiac POCUS is often used for serial monitoring of stable patients with chronic forms of heart disease.
  • POCUS can enhance diagnostic accuracy, monitoring, and screening of patients, as well as improve patient and clinician confidence and procedural safety.

8. PROGNOSIS & COMPLICATIONS

  • POCUS use for AAA screening may reduce morbidity and mortality among high-risk patients.
  • 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.
  • Ultrasound guidance for insertion of internal jugular CVCs improves procedure success rates and reduces complications, particularly pneumothorax and arterial punctures.
  • During insertion, real-time visualization of the needle tip reduces procedure attempts and needle redirections, which reduces the risk of complications.
  • POCUS can identify a safe site for paracentesis, improving procedural success and complication rates compared to landmark-based techniques.

9. SPECIAL CONSIDERATIONS

  • 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 acquisition and interpretation skills are learned at varying rates and require deliberate practice.
  • 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 residency 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 professional societies have developed POCUS training courses.
  • Clinical privileges are governed by the rules and regulations of individual 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 hospitals 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.
  • The increasing portability and affordability of ultrasound devices have allowed internal medicine clinicians to incorporate POCUS into frontline 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.

9.1 Training and Education

  • 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 acquisition and interpretation skills are learned at varying rates and require deliberate practice.
  • 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 residency 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 professional societies have developed POCUS training courses.

9.2 Credentialing and Privileges

  • Clinical privileges are governed by the rules and regulations of individual 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 hospitals 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.

9.3 Future Directions

  • The increasing portability and affordability of ultrasound devices have allowed internal medicine clinicians to incorporate POCUS into frontline 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.

10. KEY PEARLS & CLINICAL TRAPS

  • POCUS is distinct from consultative ultrasound where a clinician orders an ultrasound exam, a sonographer acquires a comprehensive set of images, an imaging 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.
  • The goal of POCUS is not to replace the imaging specialist or the high-resolution data provided by computed tomography (CT) or magnetic resonance imaging (MRI), but rather to improve diagnostic and therapeutic decisions made by the treating clinician at the bedside.
  • A noncompressible vein is diagnostic of DVT; visualization of intraluminal clot is not required to diagnose a DVT.
  • 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.
  • Identification of consolidation by lung ultrasound does not specify a diagnosis of pneumonia, and clinical correlation is required.
  • POCUS can accurately distinguish abscess from cellulitis, but diagnostic accuracy is more variable for necrotizing fasciitis.
  • POCUS use for AAA screening may reduce morbidity and mortality among high-risk patients.
  • 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.

Figures & Illustrations

Reproduced from Harrison's 22nd Edition.

Figure 1

Clinicians can use point-of-care ultrasound (POCUS) as part of a...

Caption: FIGURE 493-2 Clinicians can use point-of-care ultrasound (POCUS) as part of a of 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 point- of-care ultrasound for hospitalists. J Hosp Med 10:120, 2015.) — Figure 493-1: Workflow schematic comparing point-of-care ultrasound to physical examination and consultative ultrasound. The diagram illustrates the three different shapes representing various personnel (Bedside Clinician, Sonographer, Radiologist or Cardiologist) and curved arrows demonstrating the exchange of information among providers across different stages.

Figure 2

Workflow schematic comparing point-of-care ultrasound to physical examination and consultative...

Caption: 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.) — Figure 493-2: Clinicians can use point-of-care ultrasound (POCUS) as part of a patient's diagnosis, treatment, monitoring, and screening. The image depicts the integration of POCUS into the patient encounter workflow, beginning with history and physical, followed by focused ultrasound to narrow the differential, and guiding treatment plans and serial monitoring.

Generated from Harrison's Principles of Internal Medicine, 22nd Edition.