A Case of Recurrent Right-Sided Pleural Effusion Due to a Mediastinal Pancreatic Pseudocyst

Abstract

INTRODUCTION: The formation of a pancreatic pseudocyst in the mediastinum is an uncommon complication of alcoholic pancreatitis. The majority of documented cases have been associated with either a solitary left pleural effusion or bilateral effusions. Here we report the rare case of a recurrent right-sided pleural effusion resulting from a mediastinal pancreatic pseudocyst. CASE PRESENTATION: A 51-year-old African American male with a history of chronic alcoholic pancreatitis presented to the hospital with shortness of breath and right-sided chest discomfort. A non-contrast chest computed tomography (CT) revealed a large right pleural effusion causing complete collapse of the right middle and lower lobes. The pleural fluid was a mononuclear cell-rich exudate with an amylase level > 13,000 IU/L. The effusion rapidly recurred with symptomatic dyspnea despite multiple thoracenteses, therefore a 14-French chest tube was inserted. Three weeks after the initial CT, a contrast-enhanced chest CT showed a right pleural effusion in addition to a 5.3 × 2.4 × 5 cm mediastinal fluid collection surrounding the distal esophagus. An esophogram excluded an esophageal perforation. Magnetic resonance cholangiopancreatography (MRCP) highlighted a thin tract arising from a side branch of the main pancreatic duct and extending superiorly through the esophageal hiatus to connect with a septate pancreatic pseudocyst in the posterior mediastinum. An endoscopic retrograde cholangiopancreatography (ERCP) demonstrated marked dilation of the main pancreatic duct; pancreatic sphincterotomy was performed, followed by the placement of 2 pancreatic stents. Neither MRCP nor ERCP identified a pancreaticopleural fistula. CT imaging performed 4 weeks later revealed complete resolution of the mediastinal pseudocyst and the right pleural effusion. DISCUSSION: The differential diagnosis for an exudative pleural effusion with a high amylase level includes esophageal perforation, malignancy, tuberculous pleuritis, parapneumonic effusion, acute pancreatitis, and chronic pancreatitis with a mediastinal pseudocyst and/or pancreaticopleural fistula. It is extremely rare for a pseudocyst or fistula to manifest as a right-sided pleural effusion, as in this case. We suspect that our patient's mediastinal pseudocyst ruptured into the right pleural cavity and formed a pleural fistula. Although MRCP and/or ERCP are the most accurate modalities in demonstrating such a fistula, they fail to establish the diagnosis in 20% of cases. CONCLUSIONS: Pancreatic pathology should always be considered when evaluating a patient with a large, recurring, amylase-rich right-sided pleural effusion.