Rare case of internal pancreatic fistula in a young adult presenting with massive bilateral pleural effusion

Abstract

Pancreatic pleural fistula is a rare sequel of acute or chronic pancreatitis. The diagnosis is usually delayed due to low index of suspicion and the need for advanced diagnostic tools. The clinical presentation is often misleading because respiratory rather than abdominal symptoms predominate. The majority of reported cases of pancreatic pleural fistula present as unilateral pleural effusion; presentation as bilateral pleural effusion is extremely rare. We report a case of a 16-year-old boy with traumatic acute pancreatitis who presented with a massive bilateral pleural effusion caused by pancreatico-pleural fistula.

BACKGROUND

Internal pancreatic fistula is an uncommon complication of acute pancreatitis and commonly presents as unilateral pleural effusion. Presentation as bilateral pleural effusion is rare. This is a unique case of an internal pancreatic fistula which presented as bilateral pleural effusion and was managed without the need for surgery.

CASE PRESENTATION

A 16-year-old boy presented with a 1 month history of breathlessness and continuous dull aching pain in the upper abdomen. He was treated conservatively for acute pancreatitis due to blunt trauma 6 months ago and developed bilateral massive pleural effusion on follow-up visits 1 month after discharge. The child was referred to our hospital for dyspnoea. On presentation the patient was emaciated, anaemic and dyspnoeic with a respiratory rate of 30/min with use of accessory muscles for respiration. There was bilateral reduced air entry in the chest. Examination of the abdomen revealed tenderness in the epigastrium without any palpable lump or free fluid.

INVESTIGATIONS

Biochemical investigations revealed raised serum amylase (1300 mIU/l). The remaining blood investigations were normal. Chest radiograph revealed massive bilateral pleural effusion. Urgent bilateral intercostal chest tube insertion was performed with drainage of approximately 4 litres (2 litres on either side) of hemorrhagic pleural fluid. Pleural fluid was found to be exudative in nature with full red blood cell count and lymphocytes on cytological examination. Estimation of pleural fluid amylase was 1848 mIU/l. Magnetic resonance cholangiopancreatography (MRCP) was performed, which showed a fistulous tract extending from the main pancreatic duct towards the central portion of the diaphragm with peripancreatic fluid collection (fig 1). Endoscopic retrograde cholangiopancreatography (ERCP) showed a dilated main pancreatic duct (MPD).

Figure 1.

Magnetic resonance cholangiopancreatography showing internal pancreatic fistula (arrow).

TREATMENT

A diagnosis of pleural effusion due to pancreatic fistula was considered. The patient was started on an infusion of octreotide 200 μg every 8 h to suppress the pancreatic secretions, and was kept nil by mouth and started on total parental nutrition. Output from the chest tubes reduced from 400 ml per day to 100 ml per day, but did not stop completely even after 2 weeks. As the fistula persisted, a 5 French 7 cm stent was put in the MPD and output from the chest tubes subsequently stopped after 2 days.

OUTCOME AND FOLLOW-UP

The patient was discharged after 3 weeks. On discharge his amylase had returned to normal. He was asymptomatic without recurrence of pleural effusion at 1 year follow-up.

DISCUSSION

Pleuropulmonary complications of pancreatitis are well described. Small pleural effusions, typically left sided, occur in 3–17% of patients with acute pancreatitis and is thought to be due to chemically mediated inflammation of the diaphragm and pleura by sub-diaphragmatic collection. Pancreatic amylase concentration in the pleural fluid in these cases is either normal or mildly elevated and the effusion resolves along with the pancreatitis. Internal pancreatic fistula results from posterior disruption of the pancreatic duct into the retroperitoneal space, leading to the formation of a fistulous tract between the pancreas and the mediastinum through the aortic or oesophageal hiatus¹ where it forms a pseudo cyst. A pseudo cyst in the posterior mediastinum can rupture in one or both pleural cavities, giving rise to a large pleural effusion. A large pleural effusion rich in amylase characterises internal pancreatic fistula.

The pleural fluid amylase is usually much higher than serum amylase in cases of internal pancreatic fistula.²

In this case, disruption of the main pancreatic duct was the reason for the formation of the pancreatic pleural fistula. Other mechanisms could be the proximal pancreatic ductal stricture. The fistula develops either by direct passage of a pseudo cyst through a natural diaphragmatic hiatus or by direct fistulation through the dome of diaphragm.

Pleural effusion in these conditions is usually unilateral and left sided. Bilateral pleural effusion due to pancreatitis is extremely uncommon and so far only 20 cases have been reported.² Pleural effusion and non-specific thoracic symptoms such as pain, dyspnoea, cough, sputum production, etc, may predominate the symptomatology of the patient, whereas the abdominal symptoms are only mild. The condition is therefore often elusive, as respiratory rather than abdominal symptoms usually predominate.³ Biochemical analysis of pleural fluid is an important diagnostic tool. The amylase is always notably elevated.

Diagnosis of this complication is often delayed as the patient may have predominant chest symptoms. The first clue to pancreatic disease may be the finding of a high pleural fluid amylase concentration. MRCP can demonstrate pancreatic pathology and the fistula. It is a non-invasive alternative to ERCP and is useful when ERCP fails to give adequate information. ERCP and MRCP will identify the actual fistulous tract in 70% of cases.¹ The most definitive investigation in our view is ERCP as it has both a diagnostic as well as a therapeutic role in the management of pancreatic pleural fistula.

Initial treatment of the patient with a pancreatic pleural fistula is aimed at suppressing pancreatic activity to promote resolution of the pleural effusion and closure of the fistula.

In the past, treatment in most cases was surgical, until encouraging results were obtained with somatostatin and its analogues. Initial treatment should be directed towards control of the pleural effusion. Intercostal tube drainage, parenteral nutrition and treatment with the somatostatin analogue octreotide achieved a 48% fistula closure rate over a 2–3 week period.^3–6 Pancreatic duct stenting should be considered if the fistula fails to heal within 2–3 weeks.

LEARNING POINTS

• Massive pleural effusion after pancreatitis can be due to internal pancreatic fistula.

• Diagnosis is confirmed by very high contents of amylase in pleural fluid.

• Patients are treated by intercostal tube drainage and intravenous octreotide infusion to suppress pancreatic secretions; stenting of the main pancreatic duct should be considered if the fistula does not subside after 2–3 weeks of medical management. Surgery should be the last resort.