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.

Terminology

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

• fluid collections in interstitial edematous pancreatitis
  • acute peripancreatic fluid collections (APFC): in the first 4 weeks: non-encapsulated peripancreatic fluid collections
  • pseudocysts: develop after 4 weeks; encapsulated peripancreatic or remote fluid collections
• fluid collections in necrotizing pancreatitis
  • acute necrotic collection (ANC): in the first 4 weeks; non-encapsulated heterogeneous non-liquefied material
  • walled-off necrosis (WON/WOPN): develop after 4 weeks; encapsulated heterogeneous non-liquefied material  

Clinical presentation

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

Pathology

Pseudocysts occur from disruption of pancreatic duct structure with resulting leakage and accumulation of pancreatic juice resulting in hemorrhagic fat necrosis. They are not lined by epithelium (thus, “pseudocysts”), rather a severe inflammatory reaction results in encapsulation of the cyst by fibrosed granulation tissue. This usually takes 4-6 weeks . In approximately 50% of cases the cyst retains a communication with the pancreatic duct . Such cysts are more problematic to treat, and are more likely to recur.

Etiology

• acute or chronic pancreatitis (most common)
• pancreatic trauma
• iatrogenic, e.g. post partial gastrectomy

Radiographic features

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 .

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

Plain radiograph

Abdominal radiographs are often not sensitive in the workup for a pancreatic pseudocyst. However, if the cyst is large, it may demonstrate a gastrocolic separation sign which suggests fluid at the peripancreatic region and into the lesser sac .

Ultrasound

Hypoechoic or anechoic collections, with dependent low-level echoes representing debris, are often seen .

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 .

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

MRI

• T1
  • hypointense (fluid signal) center
  • wall demonstrates mild early enhancement, which progressively becomes more intense
• T2
  • hyperintense (fluid signal)
  • layering or dependent debris, highly specific

Treatment and prognosis

Although pancreatic pseudocyst may regress on its own and requires no further treatment, interventions are required in selected cases, particularly those complicated with infections, large size causing mass effect symptoms such as gastric outlet obstruction, bowel obstruction, hydronephrosis and biliary obstruction, diameter increasing in size or greater than 5 cm, recurrence following previous resection or aspiration, and persistent symptoms .

Treatment options include:

• open surgical debridement, or cystenterostomy with a Roux-en-Y jejunal loop
• endoscopic drainage into the stomach (or duodenum) termed a cyst-gastrostomy
• percutaneous drainage
  • remains somewhat controversial, although increasingly accepted
  • many centers report high safety and efficacy
  • critics raise concern regarding potential reaccumulation and fistula formation to the skin (especially in patients with severe pancreatitis) 
• 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 .

Differential diagnosis

General imaging differential considerations include:

• cystic lesions of the pancreas
  • do not usually have internal debris
  • may be microcystic in the case of serous cystadenoma
  • dilated duct communicating with a side branch may represent an IPMN
  • often requires endoscopic FNA for definitive diagnosis
• choledochal cyst (especially for ultrasound)
• mesenteric duplication cysts
  • very thin walls
• peripancreatic collection of acute pancreatitis
  • will not be round, but rather take on the contours of the space in which they are located
  • pseudocysts take ~4 weeks to form
• gastric duplication cyst

Siehe auch:

• Choledochuszyste
• eingeblutete Pankreaspseudozyste
• Akute Pankreatitis
• intraduktale papillär muzinöse Neoplasie
• pseudocyst
• zystische Pankreasläsionen
• seröses Zystadenom
• Walled-off-Nekrosen (WON)
• Pankreaszysten
• Pankreasabszess

und weiter:

• Bronchogene Zyste
• Pankreatitis
• zystische Läsionen der Milz
• Duplikationszyste des Magens
• Hot AXIOS Stent
• Chronische Pankreatitis
• seröses Zystadenom des Pankreas
• muzinöses Zystadenom des Pankreas
• duodenal filling defects
• nekrotisierende Pankreatitis
• Pankreaszyste
• intrapulmonary bronchogenic cyst
• antral pad sign
• splenic epidermoidcyst
• pancreatic cystadenoma
• retroperitoneale zystische Veränderungen
• Formen der akuten Pankreatitis
• intraabdominelle Liquorzele bei VP-Shunt
• Thrombose der Vena lienalis
• Duplikationszyste des Duodenums
• Pankreasruptur mit Pseudozystenbildung
• chronic pancreatitis and pseudocysts
• widened duodenal sweep by pancreatic pseudocyst
• pancreatic pseudocyst with splenic vein compression
• mikrozystisches seröres Zystadenom des Pankreas