Mediastinal Pancreatic Pseudocyst Diagnosed Based on Black Pleural Effusion

Mediastinal pancreatic pseudocysts are rare complications of pancreatitis associated with alcohol consumption. Here, we report a case of mediastinal pancreatic pseudocyst. A 61-year-old Japanese woman presented to our hospital with epigastric pain and dyspnea. A chest radiograph revealed right-sided massive pleural effusion. Thoracentesis retrieved black pleural fluid with remarkably high fluid amylase levels were. Thoracic computed tomography (CT) after drainage revealed encapsulated fluid. Magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) were performed because abdominal CT and ultrasonography did not reveal any pancreatic problems. MRCP showed cystic masses and pancreatic tail cysts extending to the stomach and lower oesophagus. ERCP confirmed leakage of contrast medium from the pancreatic tail into the retroperitoneum. We diagnosed the patient with a pancreatic pseudocyst extending to the mediastinum. A mediastinal pancreatic pseudocyst should be considered a differential diagnosis in patients with black pleural fluid with a high amylase level.