Residency · Residency · Internal Medicine
Point-of-Care Ultrasound (POCUS) in Internal Medicine
Introduction
Point-of-care ultrasound (POCUS) is a focused, bedside imaging modality performed and interpreted by the treating clinician to answer specific clinical questions. In internal medicine, POCUS has transformed the physical examination by enabling real-time visualization of anatomy and physiology, improving diagnostic accuracy, and guiding procedures.
Core POCUS Applications in Internal Medicine
Cardiac Ultrasound
- Parasternal long axis (PLAX): assess LV function, pericardial effusion, mitral and aortic valves
- Parasternal short axis (PSAX): evaluate RV strain (D-sign), regional wall motion
- Apical four-chamber: compare RV and LV size, assess global function
- Subxiphoid: best view for pericardial effusion; evaluate IVC for volume assessment
- Qualitative LV ejection fraction (hyperdynamic, normal, reduced, severely reduced) is reliable with training
Lung Ultrasound
| Finding | Appearance | Clinical Significance |
|---|---|---|
| A-lines | Horizontal reverberation artifacts | Normal aeration (or pneumothorax if no sliding) |
| B-lines (≥3/zone) | Vertical laser-like artifacts | Interstitial syndrome (edema, ILD) |
| Lung sliding present | Shimmering at pleural line | Rules out pneumothorax at that location |
| Lung sliding absent + barcode sign | No shimmering; M-mode stratospheric | Pneumothorax |
| Anechoic space above diaphragm | Dark fluid collection | Pleural effusion |
| Hepatization / tissue sign | Lung looks like liver | Consolidation / atelectasis |
- A-lines: horizontal reverberation artifacts indicating normal aeration or pneumothorax
- B-lines: vertical laser-like artifacts from pleural line; 3+ per intercostal space indicates interstitial syndrome (pulmonary edema, interstitial lung disease)
- Lung sliding: rules out pneumothorax at that location; absent sliding with barcode sign on M-mode suggests pneumothorax
- Pleural effusion: anechoic fluid above the diaphragm; estimate size and guide thoracentesis
- The BLUE protocol rapidly differentiates causes of acute dyspnea
Abdominal Ultrasound
- FAST exam (Focused Assessment with Sonography for Trauma): detects free fluid in Morrison's pouch, splenorenal recess, and pelvis
- Aorta: screen for abdominal aortic aneurysm; measure AP diameter at three levels
- Renal: identify hydronephrosis; assess bladder volume to guide catheterization
- Gallbladder: detect gallstones, wall thickening, pericholecystic fluid, sonographic Murphy sign
Vascular Ultrasound
- IVC assessment: IVC diameter and collapsibility index to estimate volume status
- IVC < 2.1 cm with > 50% collapse suggests low CVP; IVC > 2.1 cm with < 50% collapse suggests elevated CVP
- DVT assessment: two-point compression at common femoral and popliteal veins; non-compressibility indicates thrombus
- Peripheral IV access: ultrasound-guided peripheral IV placement increases first-attempt success
Volume Status Assessment: The Integrated Approach
- No single POCUS finding should be used in isolation to determine volume status
- Combine IVC assessment, lung B-lines, LV function, and pleural effusion for a comprehensive picture
- The VExUS score (Venous Excess Ultrasound Score) evaluates venous congestion through hepatic vein, portal vein, and renal vein Doppler
- Integrate POCUS findings with clinical assessment, vital signs, and laboratory data
Procedural Guidance
- Central venous catheterization: real-time ultrasound guidance is standard of care; reduces complications and improves success
- Thoracentesis: ultrasound marking or real-time guidance reduces pneumothorax risk
- Paracentesis: identify optimal entry site and avoid inferior epigastric vessels
- Arthrocentesis: improves accuracy particularly for small or difficult joints
- Lumbar puncture: identify midline, interspace level, and depth to posterior complex
Training and Competency
- The Society of Hospital Medicine (SHM) POCUS certificate program includes cardiac, lung, abdominal, vascular, and procedural modules
- Minimum recommended training: 25-50 supervised scans per application for basic competency
- Image archival and quality assurance programs should be established
- POCUS does not replace comprehensive imaging but answers focused clinical questions
- Document findings in the medical record including images
Limitations and Pitfalls
- Operator-dependent: quality varies with training and experience
- Body habitus: obesity and subcutaneous emphysema limit image quality
- Overconfidence: POCUS answers binary questions; complex pathology requires formal imaging
- Incidental findings: must be followed up with appropriate confirmatory studies
- Cannot replace echocardiography for valvular quantification or diastolic function assessment
Key Clinical Pearls
- POCUS transforms the physical examination by adding real-time visual data to clinical assessment.
- Lung ultrasound is more sensitive than chest X-ray for detecting pleural effusion, pneumothorax, and pulmonary edema.
- IVC assessment should be integrated with other POCUS findings rather than used in isolation for volume assessment.
- Ultrasound-guided procedures are standard of care for central lines and strongly recommended for thoracentesis and paracentesis.
- Competency requires structured training, supervised scanning, and ongoing quality assurance.
References
- Defined the Core Point-of-Care Ultrasound Competencies. Society of Hospital Medicine Position Statement on POCUS. Journal of Hospital Medicine. 2019;14:E1-E6.
- Lichtenstein DA, Meziere GA. Relevance of Lung Ultrasound in the Diagnosis of Acute Respiratory Failure: The BLUE Protocol. Chest. 2008;134(1):117-125.
- Defined the Core Competencies for Internal Medicine Residency. Soni NJ, Arntfield R, Kory P. Point-of-Care Ultrasound. 2nd ed. Philadelphia: Elsevier; 2019.
- Defined the Core Competencies. Franco-Sadud R, Schnobrich D, Engel D, et al. A Focused Cardiac Ultrasound Curriculum for Internal Medicine Residents. Journal of Graduate Medical Education. 2021;13(4):474-482.