Mediastinal Pancreatic Pseudocyst-A Case Report and Review of the Literature

Ruchi Gupta, MD; Juan C. Munoz, MD; Praveen Garg, MD; Ghania Masri, MD; Norris S. Nahman, Jr., MD; Louis R. Lambiase, MD

Disclosures

April 11, 2007

Discussion

We report an unusual case of a large mediastinal pseudocyst causing compression of cardiac chambers as well as the esophagus and presenting with a triad of dysphagia, chest pain and dyspnea. The interesting features about our case were the delayed onset, large size, and successful drainage of the pseudocyst using EUS-guided transesophageal approach.

Pseudocyst formation is a common complication of both acute and chronic pancreatitis. Most pseudocysts occur in peripancreatic area and very rarely do they reach the mediastinum. Pancreatic pseudocysts are cystic cavities encased by reactive granulation or fibrous tissue, in or around the pancreas. The presence of a well-defined wall distinguishes a pseudocyst from an acute fluid collection seen in acute pancreatitis. The Atlanta classification is widely used to distinguish acute fluid collection from acute and chronic pseudocysts. Acute fluid collection appears early in the course of acute pancreatitis and lacks a wall of inflammatory tissue while acute pseudocysts are composed of pancreatic fluid enclosed by a wall of inflammatory tissue and occur as a result of acute pancreatitis or trauma to the pancreas. Chronic pseudocysts, although also composed of pancreatic fluid enclosed by a wall of inflammatory tissue, occurs only as a consequence of chronic pancreatitis without any attack of preceding acute pancreatitis.[1]

Pancreatic ductal obstruction due to stricture or stones leading to an elevated intraductal pressure, results in pseudocyst formation. Pseudocyst can complicate 7% to 15% of episodes of acute pancreatitis and 20% to 25% of cases of chronic pancreatitis.[2] Spontaneous resolution occurs in more than 50% of cases but complications can occur in up to 5% to 40% of cases as reported in various studies.[3] Common complications include infection, intracystic hemorrhage, enlargement, and mass effect causing bile duct or bowel obstruction and formation of internal or external fistula.[3] The natural history, etiology, complications, and definitive treatment of mediastinal pseudocysts is still evolving due to their rare occurrence. To our knowledge, there have been about 50 case reports in world literature of mediastinal extension of pancreatic pseudocyst.[4]

It is postulated that mediastinal pseudocysts are caused by rupture of the pancreatic duct posteriorly into the retroperitoneal space. The pancreatic fluid then tracks through the diaphragmatic hiatuses into the mediastinum. Diaphragmatic openings for the esophagus and aorta are the most common sites of entry into the posterior mediastinum.[5] Symptoms are primarily the result of compression or invasion of mediastinal structures and patients may present with dysphagia, pseudoachlasia, odynophagia, dyspnea, weight loss, and/or chest pain.[6]

The diagnosis of mediastinal pseudocyst should be suspected in a patient presenting with any of the above symptoms with a history of acute or chronic pancreatitis. A chest radiograph may be nondiagnostic but can show retrocardiac opacity as in our case. Definitive diagnosis was made in our case by a CT scan showing a thin-walled low attenuation cystic mass extending from the body of pancreas into the mediastinum. Contrast-enhanced CT scan has a very high sensitivity and can provide the details regarding the location as well as the anatomic relation of the pseudocyst to the surrounding structures. Magnetic resonance imaging and magnetic resonance cholangiopancreatography (MRCP) can help identify the connection between the mediastinal and abdominal pseudocyst in cases where it is not so evident on CT scan. MRCP has similar sensitivity to ERCP and has the advantage of providing images of the ducts in their natural state because it does not involve the distension of the ducts by the injected contrast media.[7] EUS is increasingly being used in evaluating cystic lesions of the pancreas given its advantages in delineating intracystic contents and wall structures.[8] An elevated amylase level in the aspirated fluid from a mediastinal pseudocyst confirms the diagnosis.[9]

It would be interesting to speculate the cause of mediastinal pseudocyst formation in our patient. She had presented a year earlier with alcoholic pancreatitis and was discharged after an uncomplicated course. Because there was no evidence of pancreatic calcification on CT and the ERCP did not show any ductal irregularities, we assume pseudocyst formation occurred as a complication of acute pancreatitis. It would have occurred after the first episode with which she presented or during one of the episodes of self-limiting pain that could possibly have been an episode of acute pancreatitis. The slowly progressive fluid collection may have delayed the onset of symptoms and hence the delay in seeking medical attention by our patient.

Complications due to mediastinal pancreatic pseudocyst can occur due to compression, invasion, or rupture of pseudocyst into surrounding structures besides infection and hemorrhage.[6] Lymphatic interstitial edema due to compression of lymphatic flow from lungs, with obstruction of the trachea or major bronchus resulting in respiratory compromise, and retrocardiac compression leading to elevated filling pressures causing congestive cardiac failure by the enlarging pseudocyst has been described in a few case reports.[10,11] A case of mediastinal pseudocyst eroding into the pericardial sac and presenting as life-threatening tamponade has also been reported in literature.[12]

Spontaneous regression of mediastinal pseudocysts is rare.[13,14] The treatment options for this entity are dictated by the severity of symptoms, the size of the pseudocyst, the ductal anatomy, and the surgical expertise available. Medical management is supportive and includes bowel rest, nutritional support, and stomatostatin analogues. Yasuda and colleagues reported complete resolution of pleural effusion and mediastinal pseudocyst with the use of octreotide.[15]The drug acts by inhibiting pancreatic secretions and thus facilitates closure of pancreatic fistula. In most of the cases before the year 2000, surgical drainage using open laparotomy or percutaneous drainage were the chosen treatment options.[4,11,16,17] Transcutaneous external drainage can be combined with CT-guided stent placement. Complications of external drainage include bleeding, infection, clogging of catheters, permanent fistula formation, and cyst recurrence. These drainage modalities for pseudocysts limited to the abdomen, in general, have a recurrence rate of 20% and a complication rate of 15%.[11] With the advancement in endoscopic techniques, endoscopic drainage is becoming the standard of care. Endoscopic internal drainage options available are ERCP with transpapillary duct drainage combined with endoscopic stent placement or transmural drainage. All endoscopic procedures for the treatment of pancreatic pseudocysts have recurrence of less than 5% and complication rate of 10%.[11] ERCP with transpapillary stent placement can be used only when the mediastinal pseudocyst communicates with the pancreatic duct. The concept behind this is the drainage of high pressure abdominal component helps in regression of the thoracic component. Transmural drainage can be achieved by transgastric, transesophageal, or transenteric approaches. Endoscopic ultrasound is increasingly being used to guide transmural internal drainage of mediastinal pseudocyst. It helps to identify wall thickness, the site to be punctured in a nonbulging pseudocyst as well as help avoid major vessels. As per our literature search, transpapillary approach for mediastinal pseudocyst drainage has been described in approximately 5 cases and transgastric drainage in 2 cases so far.[5,9,18,19,20,21]

To our knowledge, the transesophageal approach has only been described once before in world literature.[22] Thus this may be the second time that the successful use of the transesophageal approach is being reported. Open surgical drainage should be reserved for patients in whom pancreatic necrosis, abscess, hemorrhage, or rupture of pseudocyst occurs.[11] Various drainage approaches include cystogastrostomy or cystojejunostomy, Roux en Y pancreaticoduodenostomy, and pancreaticojejunostomy should be reserved for complicated cases.

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