Pancreatic pseudocyst: These are the most common cystic lesions of the pancreas, accounting for approximately 75% of all pancreatic masses. Pancreatic pseudocysts are defined as localized amylase-rich fluid collections in or adjacent to the pancreas and surrounded by a fibrous wall that does not possess an epithelial lining. Hence, they are pseudocysts as opposed to true cysts. Postinflammatory pseudocysts are the most common cystic masses of the pancreas. They most commonly develop after acute or chronic pancreatitis, but they may also form after surgery and trauma, particularly in children. Pancreatic pseudocysts are typically solitary, but they are multiple in about 15% of patients. Two thirds of these lesions form in the tail of the pancreas. In rare cases, the collections can occur in the pelvis and even in the mediastinum. About 80% of cases are caused by alcohol or gallstone disease–related pancreatitis.

In acute pancreatitis, pseudocysts form because of ductal disruption secondary to pancreatic necrosis (postnecrotic pseudocyst) and subsequent ductal leakage that results in the extravasation of enzyme-rich pancreatic secretions and their loculation in potential spaces, including the lesser peritoneal sac and the anterior pararenal space. Most fluid collections associated with acute pancreatitis resolve spontaneously. However, those that persist for >4 weeks become encased in a fibrous capsule. Even cysts that persist >6 weeks may be followed up conservatively as long as they are <6 cm in diameter. A diameter of >6 cm usually indicates a low likelihood of complete spontaneous resolution. These relatively large cysts are associated with substantially increased morbidity rates and should be drained.

In contrast, patients with chronic pancreatitis develop pseudocysts because of elevated pressures in the pancreatic duct resulting from strictures, ductal calculi, or other causes. The elevated pressure in the duct leads to a small ductal disruption that is frequently retained in the parenchyma of the gland (retention cyst). In fact, chronic pancreatitis is the most common cause of pancreatic pseudocysts. Patients with chronic pancreatitis usually present with vague abdominal pain, early satiety, and sometimes nausea and vomiting.

The differential diagnosis of localized peripancreatic fluid collections includes cystic neoplasms (serous or mucinous cystadenomas or cystadenocarcinomas), acute pancreatic fluid collections (within 3-4 wk of acute illness), and organized pancreatic necrosis. (Patients with organized pancreatic necrosis are more ill than others.)

CT scanning is the diagnostic modality of choice and has a sensitivity of >90%. Ultrasonography and MRI are also used. Most pseudocysts resolve with expectant treatment. However, complications can occur and include infection with abscess formation, rupture into the peritoneum producing ascites, bleeding due to erosion of adjacent blood vessels, mass effect on the bile ducts that causes jaundice, and pyloric obstruction.

Drainage of pseudocysts is indicated when complications develop or when the patient becomes symptomatic. Drainage can be performed in 1 of 3 ways: surgically, percutaneously, or endoscopically by means of transmural or transpyloric approach. Surgical internal drainage (cystogastrostomy) is the criterion standard. This patient was referred to a gastroenterologist for possible endoscopic transmural drainage.