What is the significance of the wedge sign in pulmonary embolism (PE)?

From the Guidelines

The "wedge sign" is a significant radiographic finding in pulmonary embolism (PE), indicating a wedge-shaped area of lung infarction on computed tomography (CT) scans, typically with a base oriented towards the pleura and an apex pointing towards the hilum 1.

Characteristics of the Wedge Sign

• The wedge shape is characteristic due to the anatomical distribution of the pulmonary arteries and the resulting area of infarction.
• This sign is indicative of a pulmonary embolism, where a blood clot obstructs a pulmonary artery, resulting in ischemia and infarction of the downstream lung tissue.

Diagnostic Value

• The presence of a wedge sign is closely associated with PE, and was present in 15% to 45% of patients in the PISAPED study 1.
• However, the practical value of this sign in other settings remains to be demonstrated, as the chest X-rays in the PISAPED study were interpreted by experts in the field of PE diagnosis 1.

Clinical Context

• The wedge sign is one of several radiographic findings that can be used to diagnose PE, including oligemia and a pleural-based wedge-shaped infiltrate 1.
• The interpretation of lung scans may be difficult or misleading in several situations, and alternative imaging investigations are often more rewarding, such as in cases of previous pulmonary embolism, left heart failure, or chronic obstructive airways disease 1.

Key Points

• The wedge sign is a significant radiographic finding in PE, indicating a wedge-shaped area of lung infarction on CT scans.
• The presence of a wedge sign is closely associated with PE, but its practical value in other settings remains to be demonstrated.
• The interpretation of lung scans should be done in conjunction with clinical features and a current good quality chest radiograph, and direct communication between the reporter and the requesting clinician is likely to improve the value of the test 1.

From the Research

Significance of the Wedge Sign in Pulmonary Embolism (PE)

The wedge sign is a lung ultrasound finding that has been studied as a potential diagnostic tool for pulmonary embolism (PE). The significance of the wedge sign in PE can be understood through its association with pulmonary infarction and peripheral PE.

• The wedge sign is described as a possible lung ultrasound sign for pulmonary thromboembolism, consistent with pulmonary infarction and peripheral PE 2.
• Studies have investigated the role of the wedge sign, along with other lung ultrasound findings such as B-lines and pleural effusion, in the diagnosis of PE 3.
• The wedge sign has been found to be effective in the diagnosis of PE, with a moderately positive correlation with computed tomography angiography (CTA) findings 3.
• The use of lung ultrasound, including the wedge sign, has been proposed as a possible first-line approach for suspecting canine PE, due to its advantages of availability, rapidity, and lack of radiation and contrast medium 2.
• The wedge sign is also mentioned as a sign of consolidation in dogs and cats, specifically indicating pulmonary infarction, and is part of a visual lung language used in Vet BLUE, a standardized rapid lung ultrasound examination 4.

Diagnostic Accuracy of Lung Ultrasound for PE

The diagnostic accuracy of lung ultrasound for PE, including the wedge sign, has been evaluated in several studies.

• A systematic review and meta-analysis found that lung ultrasound had a bivariate weighted mean sensitivity of 87.0% and specificity of 81.8% for PE diagnosis 5.
• However, the quality of the primary studies was limited, and further well-designed accuracy studies are necessary to confirm the diagnostic value of lung ultrasound for PE 5.
• Another study found that the wedge sign, along with B-lines, was effective in the diagnosis of PE, but the sensitivity, specificity, and predictive values of lung ultrasound findings alone were low 3.