Pleural effusion and ventilation/perfusion scan interpretation for acute pulmonary embolus

Area of Science:

• Radiology
• Pulmonary Medicine
• Diagnostic Imaging

Background:

• Pleural effusions are common findings in patients with suspected pulmonary embolism (PE).
• Ventilation/perfusion (V/Q) scans are a key diagnostic tool for PE.
• The interpretation of V/Q scans can be affected by the presence and size of pleural effusions.

Purpose of the Study:

• To investigate whether the size of pleural effusions influences the interpretation of V/Q scans for diagnosing acute PE.
• To determine if current V/Q scan interpretation criteria require modification based on effusion size.

Main Methods:

• Retrospective analysis of 163 patients who underwent pulmonary angiography for PE and had radiographic pleural effusion.
• V/Q scans were analyzed in 94 patients using original Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) criteria.
• Pleural effusions were categorized as small, large, and/or bilateral, and compared with V/Q scan and angiography findings.

Main Results:

• Patients with large pleural effusions had a higher incidence of PE compared to those with small effusions or clear lungs (p < 0.05).
• V/Q-matched defects corresponding to effusion size were found in 45% of patients with PE.
• Matched V/Q defects in the presence of pleural effusions were associated with an intermediate probability of PE.

Conclusions:

• Pulmonary emboli are associated with pleural effusions of all sizes.
• V/Q scan interpretation criteria do not require revision based on pleural effusion size.
• Matched V/Q defects in pleural effusions represent an intermediate probability for PE.