Examples of Pitfalls Confusing pericardial effusion with pleural effusion Improperly measuring RV dilation Misinterpreting IVC collapse Misdiagnosing mirror artifact as lung consolidation Misdiagnosing stomach as free peritoneal fluid Over-diagnosis of acute cholecystitis Misdiagnosing rouleaux formation as DVT

Tips for Pericardial vs. Pleural Effusions Pericardial effusions will track anterior to descending aorta in parasternal long axis and apical 4-chamber views Parasternal long axis view. -Pericardial effusion (asterisks) tracks anterior to the descending aorta (da); Apical 4-chamber view. -Pericardial effusion (asterisk) tracks anterior to the descending aorta (da) -Pleural effusion (white star) tracks posterior and lateral to the da. -black arrows indicate pericardial delineation from pleura -L indicates lung consolidation

Other Tips for distinguishing Pericardial Effusion Fluid (PEF) PEF can show echotexture when it contains clots, pus or fibrin. PEF is always present in dependent segments (posterior wall, lateral wall, inferior wall) Diastolic collapse of cardiac chambers is a sign of hemodynamically significant PEF Left sided pleural effusion appears posterior and lateral to the descending aorta Ascites would appear invariably in subcostal views, anterior to the right cardiac chambers. Epicardial fat is slightly isoechoic and best observed in systole (obliterates completely in diastole) and exists exclusively in anterior regions

Epicardial fat is seen anteriorly and has echogenicity within it, while pericardial effusion is seen posteriorly or inferiorly and is anechoic, but can travel anteriorly if large enough to become a circumferential pericardial fluid collection https://www.acep.org/content.aspx?id=91918

Properly assessing RV dilation Use end diastolic measurements Assess for systolic intervetricular septum flattening and D-shaped systolic RV Always consider acute vs. chronic differential and correlate clinically (e.g. PE vs. chronic valve insuffiency, old RV infarct, chronic pulmonary HTN) RV wall thickness >5mm suggests chronically increased RV pressures

Example of D-shaped LV http://www.em.emory.edu/ultrasound/ImageWeek/Cardiac/enlarged%20rv.html

Properly Assessing IVC collapse In long axis, always anchor to avoid shifting the plane of the probe away from point of maximum vessel diameter. You can also correlate with addition of short axis views. Be aware of certain circumstances that alter the relationship between IVC measurements and volume status Examples include: Acute RV infarction Pericardial Tamponade Acute PE Asthma/COPD exacerbations Shallow respiratory effort Mechanically ventilated patients Severe tricuspid regurgitation

Mirror Artifact vs. Lung Consolidation Occurs most commonly on R side of patient due to mirror artifact of liver across diaphragm Sonographic air bronchograms, pleural fluid, and lung consolidations are not seen in mirror artifact Always correlate clinically

Peritoneal Free Fluid vs. Stomach Depending on gastric contents, sonographic imaging of the stomach can vary greatly and may be mistaken for free fluid or collection In difficult cases, ask patient to drink water or insert NG tube and observe bubbles

Avoiding misdiagnosis of Acute Cholecystitis Be aware that gallbladder distention and wall thickening are important signs of acute cholecystitis, but when found in isolation, they are not diagnostic. If you cannot visualize stones, further imaging is necessary to confirm a diagnosis of acute cholecystitis Other conditions in which gall bladder distention and wall thickening occur are listed below:

Example of wall thickening without stones in patient with heart failure

Rouleaux Formation versus DVT Rouleaux formation (also known as “sludge sign”) is the accumluation of erythrocytes overlying venous valves. On ultrasound, this appears as echogenic blood flow within the vessel that can be misdiagnosed as DVT. In contrast to thrombosis, veins with rouleaux formation are compressible In additon, compression of the distal vein clears the formation, whereas a thrombosis will not clear Doppler will show normal phasic venous wave form in rouleaux formation. If abnormal waveform is detected, correlate further with more views or other diagnostic studies.

Conclusions Always correlate clinically

References Blanco, Volpacelli. Common pitfalls in point-of-care ultrasound: a practical guide for emergency and critical care physicians. Critical Ultrasound Journal. (2016) 8:15. DOI 10.1186/s13089-016-0052-x