Lung ultrasound findings in pulmonary oedema

Pulmonology · Radiology

Acute pulmonary oedema is a potentially life-threatening condition characterised by fluid accumulation in the pulmonary interstitium and alveolar spaces, resulting in impaired gas exchange, reduced lung compliance, and respiratory distress. It commonly occurs secondary to cardiac dysfunction, myocardial ischaemia, arrhythmias, valvular abnormalities, or fluid overload. Prompt diagnosis and management are essential to prevent respiratory deterioration and adverse clinical outcomes. Lung ultrasound (LUS) has emerged as a valuable bedside imaging modality for the rapid assessment of pulmonary oedema, particularly in critically ill patients and those with acute respiratory failure. It enables real-time evaluation of lung aeration and interstitial involvement without ionising radiation. Recognition of characteristic findings, particularly B-lines, pleural line abnormalities, and their distribution, can support the diagnosis and assessment of pulmonary oedema when interpreted alongside clinical findings and other investigations.[1]Characteristic lung ultrasound findingsB-lines: B-lines are vertical, hyperechoic artifacts that arise from the pleural line, extend to the bottom of the ultrasound screen, and move synchronously with lung sliding. Multiple B-lines indicate increased pulmonary interstitial density and are commonly observed in pulmonary edemaDiffuse B-line pattern: Cardiogenic pulmonary edema typically produces multiple bilateral B-lines distributed across several lung zones, reflecting widespread interstitial fluid accumulationPleural line abnormalities: The pleural line may appear irregular or thickened in inflammatory or noncardiogenic pulmonary edema, whereas it is often relatively smooth in uncomplicated cardiogenic pulmonary edemaWhite lung appearance: When B-lines become numerous and confluent, they may produce a white lung appearance, indicating substantial loss of normal pulmonary aerationPleural effusion: Anechoic or hypoechoic fluid may be visualized in the pleural space, particularly in patients with cardiogenic pulmonary edemaDifferentiating cardiogenic and noncardiogenic pulmonary edemaCardiogenic pulmonary edema generally demonstrates bilateral, relatively symmetrical B-lines with a smooth pleural line and a homogeneous distributionNoncardiogenic pulmonary edema, including acute respiratory distress syndrome (ARDS), may demonstrate patchy B-lines, spared areas, an irregular pleural line, and subpleural consolidationsThe presence of pleural effusions may support cardiogenic pulmonary edema, although effusions are not exclusive to cardiac causesLUS findings should be interpreted alongside cardiac function, clinical history, oxygenation status, and other diagnostic investigations because B-lines are not specific to pulmonary edemaFig: Septal pattern of early Cardiogenic pulmonary edema. The pleural line is regular. B-lines are separated, laser like artefacts, spreading from the pleural line to the bottom of the screen and they show an internal sequence of alternating horizontal bands (convex probe, fundamental imaging, 6 MHz)[2]LUS examination and clinical assessmentA systematic examination should include anterior, lateral, and posterior lung regions whenever patient positioning permitsBilateral assessment helps identify the distribution and extent of interstitial abnormalitiesThe number and distribution of B-lines can be documented to assess pulmonary congestion and monitor changes over timeSerial LUS examinations may help evaluate the response to treatment and identify persistent or worsening pulmonary congestionClinical interpretation of important ultrasound patternsUltrasound patternPotential clinical significanceIsolated B-linesMay occur in normal dependent lung regions or early interstitial abnormalities.Bilateral diffuse B-linesSuggest widespread interstitial involvement, including pulmonary edema.Confluent B-linesIndicate marked reduction in lung aeration.Irregular pleural lineMay suggest inflammatory or noncardiogenic lung injury.Subpleural consolidationMay indicate focal alveolar involvement, including ARDS or infection.Pleural effusionMay accompany cardiogenic pulmonary edema or other pleural conditions.ConclusionLung ultrasound is a useful bedside tool for identifying pulmonary interstitial involvement and assessing pulmonary edema. Bilateral diffuse B-lines, their distribution, pleural line characteristics, and associated pleural effusions provide important diagnostic information. Differentiating cardiogenic from noncardiogenic patterns requires integration of ultrasound findings with clinical assessment and cardiac evaluation. Serial examinations can further support monitoring of pulmonary congestion and treatment response, making LUS a valuable component of bedside respiratory assessment.[2]Reference(s):1. Purvey M, Allen G. Managing acute pulmonary oedema. Aust Prescr. 2017;40(2):59-63. doi:10.18773/austprescr.2017.012. https://pmc.ncbi.nlm.nih.gov/articles/PMC5408000/2. Soldati G, Demi M, Demi L. Ultrasound patterns of pulmonary edema. Ann Transl Med. 2019;7(Suppl 1):S16. doi:10.21037/atm.2019.01.49. https://pmc.ncbi.nlm.nih.gov/articles/PMC6462619/