The main pathology underlying these fistulae is a persistent chronic inflammatory process of the pancreas, most often attributed to alcoholic pancreatitis [14]. PPF occurs secondary to either pancreatic duct leakage or an incomplete or ruptured pseudocyst, with pancreatic enzymes eroding the fascial planes posteriorly [15,17]. These enzymes erode into the mediastinum via the esophageal or aortic hiatus, resulting into fistula or pseudocyst communicating with the pleural cavity upon rupture [17]. An anterior pancreatic disruption is more likely to lead to ascites but can also cause a PPF [17,18]. A hydrothorax more commonly develops on the left but right or bilateral hydrothoraces have been documented [15,16,17,18].

The pleural effusion in pancreatic diseases can be either reactionary or pathological due to the fistula.  Reactionary effusions are usually small, left-sided (or may be bilateral), with amylase levels < 1000 U/L and low protein content < 3 g/dl, mostly seen in acute pancreatitis and resolve spontaneously. Effusions due to fistulae are usually large, commonly left-sided, with amylase levels >1000 u/l and high protein content > 3 g/dl, mainly  seen in  pseudocysts and chronic pancreatitis and require intervention for control.  A significantly raised pleural fluid amylase is the most important and confirmatory diagnostic test. Acute pancreatitis, pneumonia, malignancy, oesophageal perforation and pulmonary tuberculosis are also associated with raised pleural fluid amylase levels. There is no documented threshold amylase levels in the literature but a level above 50 000 IU/L, is highly suggestive of PPF. Both our patients presented with chest symptoms with high pleural fluid amylase levels i.e. 25,000 U/L and 7522 U/L respectively against a background of chronic pancreatitis suggesting the diagnosis of PPF.

The most common symptom of PPF is dyspnoea (65–76%) followed by abdominal pain, cough, chest pain, and fever [17]. These symptoms can be confused for other acute thoracic pathology, making a diagnosis and treatment challenging. Pre-disposing factors include male sex, fifth decade of life, and chronic pancreatitis secondary to alcohol, trauma, and choledocholithiasis [15,16].

The triad of previous pancreatitis, disturbance of the pancreatic duct with pleural effusion on imaging, and pleural exudate showing high amylase levels has been thought to be diagnostic of a pancreatico-pleural fistula [18].

Amylase rich pleural fluid has been documented to be black in color, prompting the consideration of diagnosis of PPF [16,19].

Diagnostic work up includes a chest radiograph followed by a CT scan to evaluate for pancreatitis and associated complications; however, the sensitivity of CT visualization is 47–63% [15]. Magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) allow for advanced visualization and therapeutic intervention respectively with sensitivity of 80% and 78% respectively [15,19]. MRI with MRCP has been found to be superior to ERCP because it provides an image of the whole pancreas as well as a possible pseudocyst. It is also able to delineate the duct of Wirsung distal to the site of obstruction.

There are no specific guidelines or approach for PF management because the data is limited. Conservative management with hemodynamic monitoring has resulted in resolution in 30-60% cases [16,20]. Conservative treatment includes complete bowel rest, total parenteral nutrition, and broad-spectrum antibiotics [16,17]. Octreotide has been used to decrease pancreatic fistula output and reduce the closing time [17]. Both therapeutic and diagnostic, thoracentesis or tube thoracostomy can measure amylase and drain symptomatic pleural effusions [18].

Medical management is usually with octreotide alone used at an initial dosage of 50 mcg TDS increasing to 250 mcg TDS. A long course of treatment for about 2 to 3 weeks is usually required and there is a low success rate of between 30 and 65% as well as needing a longer hospital stay. It is mostly useful in patients without any ductal disruption or obstruction [22]. In the setting of failed medical management or stricture, an ERCP with stent placement or sphincterotomy is warranted [15,16,17,20].

ERCP can identify the presence of a ductal stricture and the site of ductal disruption. Pancreatic stent placement provides a low resistance path for the flow of pancreatic secretions and allows mechanical closure of the site of the fistula. The duration of therapy and success rate is highly variable. A strategy of repeated ERCP every 6-8 weeks to assess fistula closure has been used by some authors [23]. Conservative management can be successful in patients with pancreatic ductal single stricture with just pancreatic stent placement, whereas patients of multiple strictures, complete duct disruption, large cysts or impacted ductal calculi are managed with surgery.

Due to inflammatory reaction around pancreas, retroperitoneal space, large vessels and surrounding organs, surgical interventions can result in severe complications including death.

In the early stage of diagnosis, it is advisable to minimize the initial surgery and total excision of the fistula may not be initially possible. The first intervention may involve drainage followed by staged surgeries when the acute inflammation resolves.

Goals of management are to restore normal anatomy and decreasing pancreatic secretions leakage, which often requires definitive surgical treatment [15,17,18,20].

Successful medical conservative management can provide resolution of fistula in 30-60% with a 15% risk of recurrence. Recommended duration of continuing conservative management is 2-3 weeks [21]. Endoscopic therapy with stent placement in the pancreatic duct is used to restore ductal anatomic continuity; it is used in cases of disruption of the pancreatic duct in the body and distal stenosis to the disruption site [21].