A pancreatic pseudocyst is a circumscribed collection of fluid rich in pancreatic enzymes, blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

, and necrotic tissue, typically located in the lesser sac

Lesser sac

The lesser sac, also known as the omental bursa, is the cavity in the abdomen that is formed by the lesser and greater omentum. Usually found in mammals, it is connected with the greater sac via the epiploic foramen...

 of the abdomen.

Pancreatic pseudocysts are usually complications of pancreatitis

Pancreatitis

Pancreatitis is inflammation of the pancreas. It occurs when pancreatic enzymes that digest food are activated in the pancreas instead of the small intestine. It may be acute – beginning suddenly and lasting a few days, or chronic – occurring over many years...

, although in children they frequently occur following abdominal trauma

Physical trauma

Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...

. Pancreatic pseudocysts account for approximately 75% of all pancreatic masses. The prefix pseudo- (Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 for "false") distinguishes them from true cyst

Cyst

A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...

s, which are lined by epithelium

Epithelium

Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

; pseudocyst

Pseudocyst

Pseudocysts are like cysts, but lack epithelial or endothelial cells. Initial management consists of general supportive care. Symptoms and complications caused by pseudocysts require surgery. CT scans are used for initial imaging of cysts, and endoscopic ultrasounds are used in differentiating...

s are lined with granulation tissue

Granulation tissue

Granulation tissue is the perfused, fibrous connective tissue that replaces a fibrin clot in healing wounds. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size it heals...

.

Pathophysiology

Acute pancreatitis results, amongst other things, in the disruption of pancreatic parenchyma and the ductal system. This results in extravasation of pancreatic enzymes which in turn digest the adjoining tissues. This results in a collection of fluid containing pancreatic enzymes, hemolysed blood and necrotic debris around the pancreas. The lesser sac

Lesser sac

The lesser sac, also known as the omental bursa, is the cavity in the abdomen that is formed by the lesser and greater omentum. Usually found in mammals, it is connected with the greater sac via the epiploic foramen...

 being a potential space, the fluid collects here preferentially. This is called an acute pancreatic collection. Some of these collections resolve on their own as the patient recovers from the acute episode. However, others become more organized and get walled-off within a thick wall of granulation tissue and fibrosis. This takes several weeks to occur and results in a pancreatic pseudocyst.

Diagnosis

The questions that need to be answered are:

• where, how big and how many?
• is there a communication with the pancreatic ductal system? Draining such a pseudocyst carries an increased risk of pancreatic fistula.

The most useful imaging tools are

• Ultrasonography - The role of ultrasonography in imaging the pancreas is limited by patient habitus, operator experience and the fact that the pancreas lies behind the stomach (and so a gas-filled stomach will obscure the pancreas).
• Computerized tomography - This is the gold standard for initial assessment and follow-up
• Magnetic resonance cholangiopancreatography
  Magnetic resonance cholangiopancreatography
  Magnetic resonance cholangiopancreatography is a medical imaging technique that uses magnetic resonance imaging to visualise the biliary and pancreatic ducts in a non-invasive manner...
  
   (MRCP) - to establish the relationship of the pseudocyst to the pancreatic ducts

Treatment

A small pseudocyst that is not causing any symptoms may be managed conservatively. However, a large proportion of them will need some form of treatment, The interventions available are:

• Endoscopic trans-gastric drainage
• Imaging guided percutaneous drainage
• Laparoscopic/open cystogastrostomy or cystojejunostomy

Complications

Complication of pancreatic pseudocyst include infection, hemorrhage, obstruction and rupture. For obstruction, it can cause compression in the GI tract from the stomach to colon, compression in urinary system, biliary system, and arteriovenous system.