Pancreatic pseudocyst

Pancreatic pseudocysts are common sequelae of acute pancreatitis or chronic pancreatitis, and the most common cystic lesion of the pancreas. They are important both in terms of management and differentiation from other cystic processes or masses in this region.

The following are the latest terms according to the updated Atlanta classification to describe fluid collections associated with acute pancreatitis 10,11:

Pancreatic pseudocysts are frequently found on imaging follow-up of pancreatitis, and may in themselves be asymptomatic for some time. Presentations attributable to a pseudocyst include:

  • mass effect
    • biliary obstruction
    • gastric outlet obstruction
  • secondary infection

Pseudocysts occur from disruption of pancreatic duct structure with resulting leakage and accumulation of pancreatic juice resulting in haemorrhagic fat necrosis. A severe inflammatory reaction that is incited by this results in encapsulation of the cyst by fibrous tissue. This usually takes 4-6 weeks 8-9. In approximately 50% of cases the cyst retains a communication with the pancreatic duct 2. Such cysts are more problematic to treat, and are more likely to recur.

Aetiology

Pseudocysts are fluid filled oval or round collections with a relatively thick wall. They can be multiple and are most commonly located in the pancreatic bed. However, they can be found anywhere from the groin to the mediastinum and even in the neck, having ascended in the retroperitoneum via the diaphragmatic hiatuses into the mediastinum 5

It is not possible to reliably distinguish infected from non-infected pseudocysts on imaging alone 9.

Ultrasound

Hypoechoic or anechoic collections with low-level echoes are often seen dependently representing debris 8.

CT

Pseudocysts appear as well-circumscribed, usually round or oval peripancreatic fluid collections of homogeneously low attenuation, that are usually surrounded by a well-defined enhancing wall 10

According to the revised Atlanta classification, pseudocysts contain no non-liquefied components within the fluid collection 10.

MRI
  • T1
    • hypo-intense (fluid signal) centre
    • wall demonstrates mild early enhancement, which progressively becomes more intense 7
  • T2
    • hyperintense (fluid signal)
    • layering or dependent debris, highly specific 6

Treatment of pseudocysts depends on size and presence of superimposed infection, as well as local mass effect (usually related to size). If the cysts are small (less than 4-6 cm) they mostly resolve spontaneously. Approximately half of all pseudocysts resolve spontaneously 2,3. Indications for drainage include 1:

Treatment options include:

  • open surgical debridement, or cystenterostomy with a Roux-en-Y jejunal loop 3
  • endoscopic drainage into the stomach (or duodenum) 3
  • percutaneous drainage
    • remains somewhat controversial, although increasingly accepted 1-2
    • many centres report high safety and efficacy 1
    • critics raise concern regarding potential reaccumulation and fistula formation to the skin (especially in patients with severe pancreatitis) 4
  • Octreotide infusion: decreases amount of pancreatic secretions

Cysts that do not communicate with the pancreatic duct usually do not recur, and are unlikely to create fistulae 2.

General imaging differential considerations include:


Pancreatic pathology
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Article Information

rID: 6938
Section: Pathology
Synonyms or Alternate Spellings:
  • Pancreatic pseudocysts
  • Pancreatic pseudocyst
  • Pseudocysts of the pancreas
  • Pseudocyst of the pancreas
  • Pseudocysts of pancreas
  • Pseudocyst of pancreas

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