Department of Surgical Gastroenterology and Liver transplant, Sir Gangaram Hospital, New Delhi.

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Pancreatic fistula is a rare complication of acute pancreatitis, chronic pancreatitis and pancreatic trauma. It develops because of pancreatic ductal disruption or rupture of a pseudocyst. Pancreatic ascites develops due to free secretion of pancreatic juice into peritoneal cavity. Pancreatico-pleural fistula formation is a very rare complication of chronic pancreatitis and even more rarely seen in acute pancreatitis [1,2]. Its challenging to diagnose this rare complication and even more challenging to treat it adequately [3-5]. Left pleura is the most common location for pancreatic fistula followed by right pleura and both pleural cavities [6]. Such exudative pleural effusions can cause chest pain and dyspnoea, like any emergent thoracic pathology e.g., aortic dissection; as a result, this diagnosis is challenging to identify. Pancreaticopleural fistula occurs in 0.4% of patients with acute pancreatitis [7,8], in 4.5% of patients with pancreatic pseudocyst and in 20-30% cases of untreated chronic pancreatitis [9,10]. The pleural effusion associated with pancreaticopleural fistula is typically refractory to drainage and tends to accumulate rapidly [7]. Thoracocentesis with measurement of amylase in pleural fluid is the most important diagnostic procedure followed by MRCP or CT for the anatomy of fistulous tract [11]. The management is based on three lines of treatment: the first is the conservative medical management which includes suspension of the oral intake, initiation of total parenteral nutrition and administration of somatostatin analogues; the second line is based on endoscopic management by placing a stent in the pancreatic duct, and the third line is the surgical option, consisting of surgical resection (distal pancreatectomy) and enteric shunts (pancreatojejunostomy or cystojejunostomy) [12]. In this article, we delve into the clinical narratives of two distinct cases that shine a spotlight on the complexities of pancreatico-pleural fistulas. These cases not only underscore the clinical heterogeneity associated with this condition but also emphasize the importance of a comprehensive evaluation and a patient-tailored therapeutic strategy.

A 37 years old male presented with history of cough with expectoration for 5 months and dyspnea for 3 months which gradually increased over last 4 weeks. Patient was diagnosed to have chronic calcific pancreatitis for 5 years and he was on oral pancreatic enzyme supplementations and oral analgesics for pain relief. Patient was not a smoker and not an alcoholic. Patient was hemodynamically stable and was admitted under thoracic unit. His vital parameters were stable and was maintaining room air saturation 98%. Blood evaluation was unremarkable. His chest X-ray [Fig.1] was suggestive of left sided pleural effusion. Intravenous contrast enhanced CT chest and abdomen [Fig.2,3] showed atrophic pancreas with intra-pancreatic calcification, dilated main pancreatic duct (maximum diameter 10 mm) throughout pancreas and left sided pleural effusion. There was a fistulous tract of size 5 mm diameter and 15 mm length between pancreatic body and left pleural cavity. Left intercostal drainage tube was inserted and the fluid analysis showed high amylase value (25000 U/L). Referral was sought of department of surgical gastroenterology for management of pancreatico-pleural fistula. After thorough counseling about risks and benefits of intervention with family members of the patient, patient underwent laparotomy. Intra-operatively fistulous tract was seen arising from body of pancreas [Fig.4]. Hence division of fistulous tract with Roux-en-Y fistulo-jejunostomy with externalization of anastomotic stent was performed [Fig.5]. Post-operative period was uneventful. Repeat ICD drain fluid amylase was found to be undetected. Patient recovered well and was discharged on day 10 with an anastomotic external stent which was removed after 6 weeks. Patient is doing well on 5 years of follow up.

A 35 years old male patient presented with right sided chest pain for 1 month and dyspnea for 1 week. Patient had history of recurrent upper abdominal pain for past 2 years. He was diagnosed to have chronic calcific pancreatitis and was managed conservatively by oral analgesics and pancreatic enzyme supplementation. Patient was a chronic smoker for 10 years and he used to consume alcohol daily for 7 years. Patient was admitted at local hospital where chest X-ray [Fig.6] was suggestive of right sided pleural effusion and hence right sided intercostal drainage tube was placed and he was referred to our center. Patient had stable vital parameters and normal room air saturation on admission. On blood evaluation, patient had severe hypoalbuminemia (1.6 gm/dL) with raised serum amylase (370 U/L) and raised serum lipase (158 U/L). Rest of the laboratory tests were normal. IV contrast enhanced CT chest and abdomen [Fig.7-9] showed calcifications in head of pancreas, dilated MPD, peri-pancreatic region collection without MPD communication and right sided intra-thoracic fistulous extension causing right pleural effusion with collapse of underlying lung parenchyma suggestive of chronic calcific pancreatitis with pancreatico-pleural fistula. Drain fluid amylase was 7522 U/L. After detailed counseling, patient underwent Frey’s procedure [Fig.10], drainage of peri-pancreatic fluid collection and division of fistulous tract. Post-operative period was uneventful and patient recovered well. ICD tube was removed on day 5 once drain fluid analysis showed undetectable amylase level. Patient is doing well on 4 years of follow up.

The main pathology underlying these fistulae is a persistent chronic inflammatory process of the pancreas, most often attributed to alcoholic pancreatitis [13,14]. PPF occurs secondary to either pancreatic duct leakage or an incomplete or ruptured pseudocyst, with pancreatic enzymes eroding the fascial planes posteriorly [15,16]. These enzymes erode into the mediastinum via the esophageal or aortic hiatus, resulting into fistula or pseudocyst communicating with the pleural cavity upon rupture [16]. An anterior pancreatic disruption is more likely to lead to ascites but can also cause a PPF [16,17]. A hydrothorax more commonly develops on the left but right or bilateral hydrothoraces have been documented [15-17]. 

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 [16]. 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 [7,10]. 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 [14]. Amylase rich pleural fluid has been documented to be black in color, prompting the consideration of diagnosis of PPF [10,15]. 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% [7]. Magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) allow for advanced visualization and therapeutic intervention respectively with sensitivity of 80% and 78% respectively [7,15]. 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.

A pancreatico-pleural fistula is a rare complication and a challenging diagnosis in patients with chronic pancreatitis and requires thorough evaluation in patients presenting with recurrent respiratory symptoms in the background of pancreatitis. Significantly raised pleural fluid amylase levels with MRCP to delineate the pancreatic ductal anatomy are useful in making the diagnosis and deciding the further management. Conservative medical management by somatostatin analogues and endoscopic stenting have a low success rate and surgical intervention often offers the best chance of cure. 

Contributors: NS: manuscript writing, patient management; NM: chief operating surgeon case 1 and manuscript editing; VM: chief operating surgeon case 1 and manuscript editing; RJ: radiological and intraoperative details; SN: critical inputs into the manuscript. NS will act as a study guarantor. All authors approved the final version of this manuscript and are responsible for all aspects of this study.

Funding: None; Competing interests: None stated.