30 years old male patient came to chest OPD with pain in right side of chest and cough for past 3 weeks. On examination, decreased breath sounds were heard in basal segment of right lung. Chest x-ray revealed obscuration of bilateral CP angle. Subsequently CECT chest was done . Most probable diagnosis is?

The split pleura sign is seen with pleural empyemas and is considered the most reliable CT sign helping to distinguish empyemas from noninfectious pleural effusions. The sign results from fibrin coating of both the parietal and visceral surface of the pleura with resulting in growth of blood vessels. Following IV contrast injection CT shows a loculated fluid collection and thickened pleural layers with accompanying enhancement. Both layers of the pleura can then be visualized as linear regions of enhancement that divide around a less dense empyema or in other words come together at the margins of the collection.