A pancreatic pseudocyst is a fluid-filled collection encapsulated by a well-defined wall of fibrous and granulation tissue, arising as a complication of acute or chronic pancreatitis or following pancreatic trauma. Unlike true pancreatic cysts, a pseudocyst has no epithelial lining hence the prefix "pseudo" and its contents are rich in pancreatic enzymes, particularly amylase and lipase, which leak from disrupted pancreatic ducts. It is the most common cystic lesion of the pancreas, occurring in approximately 10–20% of cases of acute pancreatitis and up to 40% of cases of chronic pancreatitis. The majority develop in the body or tail of the pancreas and can range in size from a few centimetres to massive collections occupying a significant portion of the abdominal cavity. While many small pseudocysts resolve spontaneously, large or persistently symptomatic ones carry a risk of serious complications including infection, haemorrhage and rupture.
Symptoms
Small pancreatic pseudocysts may be entirely asymptomatic and discovered incidentally on imaging. When symptomatic, the most consistent feature is persistent or worsening upper abdominal pain radiating to the back reflecting ongoing ductal hypertension and local inflammatory irritation. A palpable epigastric mass may be detected on examination when the pseudocyst reaches a significant size. Compression of adjacent structures produces a characteristic constellation of symptoms: gastric compression causes early satiety, nausea and vomiting; biliary compression causes obstructive jaundice and duodenal compression causes gastric outlet obstruction. Systemic features including fever, malaise and weight loss raise concern for secondary infection of the pseudocyst a serious complication producing an infected pseudocyst or pancreatic abscess requiring urgent drainage.
Diagnosis
CT scan of the abdomen with contrast is the gold standard investigation, demonstrating a well-defined, thin-walled, homogeneous fluid collection typically of low attenuation adjacent to the pancreas, without internal solid components or septations that would raise suspicion for a cystic neoplasm. MRI with MRCP provides superior soft tissue characterisation and is particularly valuable in delineating the relationship between the pseudocyst and the main pancreatic duct critical information for planning drainage strategy. Endoscopic Ultrasound (EUS) with fine-needle aspiration of cyst fluid allows biochemical and cytological analysis; markedly elevated amylase in the aspirate confirms the diagnosis of pseudocyst and distinguishes it from mucinous cystic neoplasms, which carry malignant potential. Serum amylase and lipase are typically elevated during the acute phase but may normalise as the pseudocyst matures.
Treatment
Asymptomatic pseudocysts less than 6 cm in diameter are managed conservatively with clinical and radiological surveillance, as a substantial proportion particularly those following acute pancreatitis resolve spontaneously within 4–6 weeks. Intervention is indicated for pseudocysts that are symptomatic, enlarging, infected or failing to resolve after 6 weeks. Endoscopic Ultrasound-guided Transmural Drainage (EUS-TD) is now the preferred first-line interventional approach, in which the pseudocyst is accessed and drained endoscopically through the stomach (cystgastrostomy) or duodenum (cystduodenostomy) under EUS guidance, with placement of a stent to maintain the drainage tract. This minimally invasive technique achieves high success rates with low complication rates in experienced hands. Surgical internal drainage most commonly a cystgastrostomy or Roux-en-Y cystjejunostomy remains the definitive option when endoscopic drainage fails or is anatomically unfeasible, and continues to offer durable long-term results. Percutaneous CT-guided external drainage is reserved for infected pseudocysts or pancreatic abscesses where urgent source control is required, though it carries the risk of creating a persistent pancreatic fistula.