Case Presentation: Here, we present a rare case of large bilateral pleural effusions arising from a pancreaticopleural fistula (PPF) with a complicated course of trapped lung. Our patient is a 41 year old woman with a history of chronic pancreatitis who presented to the emergency department with a 3-day history of dyspnea on exertion and orthopnea. Chest x-ray demonstrated large pleural effusions with predominantly perihilar alveolar opacities (Figure 1). Therapeutic thoracentesis revealed serosanguinous pleural fluid with an amylase of 630 U/L and lipase of 805 U/L. CT abdomen was notable for enlargement of the pancreatic duct and a stable pancreatic pseudocyst. Chest x-ray after left pigtail catheter placement demonstrated re-expansion of the right pleural effusion and new left hydropneumothorax concerning for persistent trapped lung with ex vacuo findings (Figure 2). Left lung video assisted thoracoscopic surgery (VATS) decortication for the treatment of trapped lung was performed. ERCP was performed to evaluate for a pancreatic source of the pleural effusions and demonstrated a dilated pancreatic duct and leakage at the tail or upstream body, likely representing a fistula to the pleura. Sphincterotomy with stent placement was performed to promote flow of pancreatic secretions internally and facilitate PPF closure.

Discussion: PPF is a rare complication of acute or chronic pancreatitis that typically occurs in the setting of a pseudocyst that communicates with the pleural cavity, or through a channel between the pancreatic duct and pleura [1]. It commonly presents as a recurrent left-sided pleural effusion that is diagnostically positive for amylase or lipase [2,3]. As the most common presenting clinical symptoms of dyspnea, cough, and chest pain more commonly point towards a pulmonary or cardiac etiology, diagnosis of PPF is often delayed and allows for the development of complications such as lung entrapment. In the case of our patient, the pleural fluid amylase level of 630 U/L was significantly lower than typically found in PPFs which are usually greater than 1,000 U/L and can reach greater than 6,000 U/L. Further, our patient presented with bilateral pleural effusions which only occurs in approximately 14-16% of PPF cases [4]. Before we could perform a diagnostic ERCP to determine a pancreatic etiology of our patient’s bilateral pleural effusions, the clinical course of our patient became complicated by the development of trapped lung. Trapped lung usually presents as a pleural effusion that is unable to be completely drained, or as a post-thoracentesis hydropneumothorax as in the case of our patient [5]. Trapped lung occurring in the setting of a PPF is extremely rare with only a few reported cases resulting from a unilateral pleural effusion [2,6,7]. Surgical treatment with decortication was successfully utilized in one of these cases, as in our patient who presented with bilateral pleural effusions [7].

Conclusions: To our knowledge, this is the first documented case of PPF leading to bilateral pleural effusions with resultant development of a trapped lung. Although a rare occurrence, it is essential that PPFs be included in the differential diagnoses when presented with an inpatient case of persistent bilateral pleural effusions if the patient has a history of pancreatitis as early diagnosis may prevent complications such as trapped lung. Detection of amylase or lipase in the pleural fluid along with diagnostic imaging via ERCP or MRCP is imperative to confirming the diagnosis.

IMAGE 1: Chest x-ray obtained in emergency department demonstrating large left pleural effusion and moderate-to-large right pleural effusion.

IMAGE 2: Chest x-ray demonstrating loculated left pneumothorax with concern for trapped lung.