What is the anatomy and management of a pancreatic pseudocyst?

Pancreatic Pseudocyst: Anatomy and Management

Anatomic Definition

A pancreatic pseudocyst is a collection of pancreatic juice enclosed by a wall of fibrous or granulation tissue that arises following an attack of acute pancreatitis, requiring four or more weeks from onset to form. 1

Key Anatomic Features

• Wall composition: The pseudocyst wall consists of fibrous or granulation tissue, distinguishing it from acute fluid collections which lack this organized wall structure 1
• Contents: Fluid rich in amylase and pancreatic enzymes 2
• Location: Typically located in or near the pancreas, though can extend to involve adjacent structures including the gastric wall (intramural location) 3
• Timing: By definition, cannot be diagnosed before 4 weeks after the onset of acute pancreatitis 1, 4

Distinction from Other Collections

• Acute fluid collections occur early in pancreatitis and always lack a wall of granulation or fibrous tissue 1
• Pancreatic abscess contains pus with little or no pancreatic necrosis 1
• Infected necrosis involves non-viable pancreatic parenchyma with infection, tripling mortality risk 1

Important caveat: All localized collections following necrotizing pancreatitis should be considered localized necrosis until proven otherwise with definite imaging evidence of fluid rather than necrotic tissue 1

Diagnostic Approach

Imaging Modalities

• CT scanning is the most common diagnostic tool, though cannot reliably distinguish pseudocyst from other peripancreatic collections alone 1, 5
• Ultrasound or MRI should be obtained to confirm fluid (as opposed to necrotic tissue) before diagnosing pseudocyst 1
• CT attenuation values of 59 Hounsfield units indicate high protein or blood content within the pseudocyst 3
• MRI characteristics: Hemorrhagic cysts show heterogeneous hyperintensity on both T1 and T2-weighted sequences 3
• Endoscopic ultrasound with cyst fluid analysis can be performed in cases of diagnostic uncertainty 4

Management Strategy

Observation vs Intervention

More than half of acute fluid collections resolve spontaneously, and in otherwise stable patients they do not require treatment. 1

Indications for Intervention

• Symptomatic pseudocysts with persistent abdominal pain 4
• Complications: biliary obstruction, gastric outlet obstruction, hemorrhage, infection, or rupture 4
• Giant pseudocysts (>10 cm) are associated with significantly higher morbidity (65%) and mortality (18%) compared to smaller pseudocysts 6
• Patients with high Ranson scores are at significant risk for giant pseudocyst formation and may benefit from earlier external drainage before clinical deterioration 6

Treatment Modalities

Endoscopic drainage should be the first-line approach when anatomically feasible, given high success rates and lower complication/mortality rates compared to surgery. 7, 2

Endoscopic Options

• Transpapillary drainage or transmural drainage depending on anatomy and topography 5, 7
• EUS-guided drainage decreases risks associated with conventional endoscopic drainage 2
• Provides high success and low complication rates when feasible 5, 7

Percutaneous Drainage

• Used primarily for infected pseudocysts 5, 7
• Usefulness in chronic pancreatitis-associated pseudocysts is questionable 5, 7
• Risk of introducing infection with unnecessary percutaneous procedures 1

Surgical Intervention

• Reserved for cases where endoscopic approaches fail or are not feasible 2
• Internal drainage (cystogastrostomy) for mature pseudocysts 6
• External drainage for urgent situations or immature pseudocysts 6
• Pseudocyst resection in selected cases 5
• Higher morbidity and mortality compared to endoscopic intervention 5, 7

Size-Based Considerations

• Small pseudocysts (<10 cm): Internal drainage associated with 10% mortality and 10% morbidity 6
• Giant pseudocysts (>10 cm): Expectant management associated with 65% morbidity and 18% mortality; earlier external drainage before clinical deterioration may be beneficial 6
• Comparisons of treatment outcomes must account for pseudocyst size to be accurate 6

Timing of Intervention

• Traditional approach advocated observation to allow cyst maturation 6
• Current evidence suggests selective approach with earlier intervention for giant pseudocysts or those with high-risk features 6
• Repeat CT scanning every two weeks in severe cases to monitor for complications 1

Complications Requiring Urgent Management

• Hemorrhage: CT attenuation values >50 HU suggest blood content 3
• Infection: Indicated by sudden high fever, though unremitting low-grade fever is common in necrotizing pancreatitis without necessarily indicating infection 1
• Rupture: Free gas in retroperitoneum on plain films is a late sign of infection with gas-forming organisms 1
• Biliary or gastric outlet obstruction: Epigastric mass with vomiting suggests persistent fluid collection 1

Management in Specialist Units

Patients with extensive necrotizing pancreatitis or complications should be managed in or referred to specialist units with multidisciplinary expertise, full intensive care facilities, emergency ERCP capability, and expert radiological support for percutaneous procedures 1