An esophageal rupture is going to cause a huge amount of local irritation. Combine that with extended intense vomiting (extreme fluctuations in intrathoracic pressure) and you have a highly agitated area that is going to be recruiting a lot of inflammatory agents. This is enough, in my eyes, to cause a pleural effusion. The question that arises is "Is the esophageal rupture due to extended vomiting or has the esophageal and surrounding connective tissue been compromised by tumor or abscess or whatever?" The patient has probably also aspirated during the episodes. That's just my thoughts.
