Pancreatic Pseudocyst (and Pancreatic ductal disruption)

Definition
A collection of pancreatic juice enclosed by an fibrous inflammatory wall.
- pseudo because it is not lined by epithelium.
- cause symptoms if: 1) compress adjacent structures; ii) get infected; iii) rupture

Epidemiology
Up to 16-50% of acute pancreatitis

Aetiology
Pancreatitis
Or pancreatic trauma
--> arise from disruption of major or minor pancreatic ducts following inflammation or injury.
Chronic pancreatitis
- chronic fibrosis, duct irregularity, duct obstruction and dilation --> duct disruption, producing the pseudocyst
- diagnostic problem as difficult to know if problem is the pseudocyst or necrosis / ductal obstruction.

Pathophysiology
(As per Revised Atlanta Criteria)
Majority of pancreatic collections resolve
- some fail to; enzymes incite a local inflammatory response
--> walled off with fibroblasts accumulating and laying down a thick capsule
May be intra-pancreatic, but usually extra, occupying the lesser sac.
- may also involve small bowel mesentery, transverse mesocolon, or behind right and left colons.
Traditionally stated that it takes 4-6 weeks at least to appear from onset of pancreatitis
- with modern imaging, if can identify a clear wall earlier, then it is a pseudocyst not an acute fluid collection.
Leakage or rupture --> pancreatic ascites
- can be branch, main duct, or if severe disease, a whole necrotic pancreatic tail disruption.
- may cause a pancreaticopleural fistula
- if infected = pancreatic abscess
Most communicated with the duct and contain watery fluid rich in enzymes
- most have persistent elevations of enzymes in serum.
May occur singly, or as small multiple cysts.
If >6cm, symptoms more likely (tender, mass effect)
- gastric outlet obstruction may occur, or compress stomach with early satiety.
- obstructive jaundice may similarly occur.
- can rupture

'Pancreatic Ductal Disruption'
Another state where pancreatic ascites or pleural effusions follow enzyme-rich fluid spilling beyond pancreas.
In general, where there is a duct disruption, the duct should be addressed.
- pancreatic fluid collections; may be trivial leak from ductules or persisting leak from a major duct.
- pseudocysts (most common complication of duct disruption)
- organized pancreatic necrosis (after nec. panc.).
- pancreatic fistula, often a complication of pancreatic resections or damage; can be persistent drainage
- pancreatic ascites; generally causes peritonitis; initial collection is in the lesser sac.
- pancreatic pleural effusions; enzyme rich fluid may traverse foramina to cause thoracic sequelae
Anatomy
Duct anatomy is important for management, whether there is stricturing, obstruction, disruption or leak.
- will help guide conservative vs transpapillary stenting etc.
Location: more common in head (50%) vs body (30%) and tail (20%) but this doesn't change management much.
Presentation
Most will show acute +/- persisting fluid collections in context of their underlying disease
But some will present with recurrent pancreatitis and recurrent pain.
Management of ductal disruptions
Supportive measures as per cause, and intervene for complications or symptoms.
Endoscopic, surgical and percutaneous approaches used, as discussed further below re pseudocysts.

Manifestations
Mass effect
Abdominal pain
Nausea and vomiting
Early satiety
Possibly weight loss from obstruction
Occasionally jaundice
Even lower extremity oedema from IVC obstruction.
Infection
Systemic upset.
Other
portal, SM or splenic vein thrombosis
Rupture
Severe abdominal pain (from pancreatic ascites)
Haemorrhage
from erosion into GI tract mucosa or vessels

Investigations
US
Cheap and effective
Can show the cystic mass but poor for anatomy of relationships.
CT
Primary means of imaging
Rounded, fluid-filled mass, defined wall of uniform thickness.
Evaluate pancreas for pathology; necrosis, atrophy, calcification, dilatation.
Though difficult to see duct status from CT
MRI
Helpful to differentiate pseudocyst and cystic neoplasm.
Excellent soft-tissue contrast capability; may show cyst wall irregularities and septations suggestive of neoplasms.
- internal dependent debris is highly specific for pseudocyst.
If concern for neoplastic cyst, then need aspiration and analysis, e.g. via EUS-FNA.
- analyze fluid for tumor and genetic markers, mucin, enzymes and cells, gram stain and culture
MRCP / ERCP
Can show connections between main ducts and pseudocysts.
Don't want to introduce infection though; MRCP reduces this risk vs ERCP.

Management
Conservative
Many can be managed conservatively.
- 40% resolve within 6 weeks
- those that don't continue to resolve over up to a year, and complication rate is low <10cm.
- even large cysts can be safely observed, despite lower invasiveness of modern interventions.
- less likely to resolve if >5cm
Perform serial imaging (e.g. 6 weekly or 3 monthly); those that are enlarging may require intervention

MRCP / ERCP
Prior to intervention to define anatomy and exclude strictures preventing resolution

Interventions

If symptomatic, enlarging, or causing complications, may need therapy
Various options, eg cystjejunostomy, distal pancreatectomy...
But pseudocyst drainage is now the usual pathway
- percutaneous catheter drainage in poor candidates, but introduces infection and morbidity, plus external fistula formation is slow to resolve.
- no evidence for benefit of octreotide.

Internal drainage now preferable:
- 85% success
- endoscopically via transpapillary drainage (esp for head cysts, but can lead to infection), cyst-gastrostomy or cyst-duodenostomy
--> USS, avoid vessels, aspirate to confirm diagnosis, then drain by incising through wall of stomach / duodenum, place a stent
- in some instances, endoscopic dilation with a balloon catheter can help to widen the opening and to facilitate drainage.
Transpapillary drainage aims to stent across the duct, excluding the communication to the cyst, permitting healing without drainage.
Surgically treated via cyst-gastrostomy, cyst-duodenostomy or Roux-en-Y cyst-jejunostomy.

Treatment Suggestions
1. Pseudocyst after pancreatitis
- persistent communication with ductal system should be suspected.
Transpapillary approach for those in proximity with main duct
Else cyst-gastrostomy (endoscopic)
For ones that are difficult to drain due to anatomical location
- perform MRCP to determine ductal communication.
- if isolated --> drain percutaneously
- if communication --> Roux-en-Y cystojejunostomy
If septic, drain externally.

2. Pseudocysts with pancreatic necrosis.
- usually associated with significant ductal disruption and thick contents.
Image to determine quantity and nature of debris (MRI)
Intervention tailored to indications
- drain infection
internal drainage if possible.

3. Chronic pancreatitis
- structured ducts, difficult to separate symptoms
Transpapillary approaches in a specialist unit.

Method: Open Cyst-gastrostomy
longitudinal anterior gastrostomy
Needle aspiration to locate pseudocyst if not obvious.
Open gastric wall and cyst cavity
Send a section of the wall for histological analysis.
Running locking suture (2-0 PDS joining cyst wall to stomach wall.
When not directly adherent to stomach, can do Roux drainage.
If concerned re malignancy, surgical resection.