Pancreatic Pseudocysts

Pseudocysts are best defined as localized fluid collections that are rich in amylase and other pancreatic enzymes, that have a nonepithelialized wall consisting of fibrous and granulation tissue, and usually appears several weeks after the onset of pancreatitis.[1]

These characteristics contrast with those of acute fluid collections, which are more evanescent and are serosanguinous inflammatory reactions to acute pancreatitis. These collections are noted in moderate-to-severe pancreatitis. Acute fluid collections usually have an irregular shape and lack a well-defined wall. In general, they resolve in about 65% of cases.

Two other types of fluid collection should be considered. First, an organized necrosis is actually devitalized pancreatic tissue that appears cystlike on computed tomography (CT) scans, but it appears to be solid on other imaging modalities. Second, an abscess is an infected area of necrosis or fluid.

Acute or, rarely, chronic pancreatitis or abdominal trauma causes pseudocysts. If no history of pancreatitis or trauma exists, the diagnosis must be carefully confirmed.

Single or multiple fluid collections that look like cysts on pancreatic imaging are often observed during acute pancreatitis. Because of increasing sensitivity of imaging modalities and improvements in technology providing enhanced therapeutic abilities, the question arises as to when and whether drainage should be performed and what modality should be used to drain the cysts.[2] Strictly defining the type of fluid collection is very important when reviewing pancreatic fluid collections. The therapeutic approach is different depending on the type of collection.

Pancreatic pseudocysts can be single or multiple. Multiple cysts are more frequently observed in patients with alcoholism, and they can be multiple in about 15% of cases. Size varies from 2-30 cm. About one third of pseudocysts manifest in the head of the gland, and two thirds appear in the tail. The fluid in pseudocysts has been well characterized as clear or watery, or it can be xanthochromic. The fluid in pseudocysts usually contains very high amounts of amylase, lipase, and trypsin, though the amylase level may decrease over time.

The pathogenesis of pseudocysts seems to stem from disruptions of the pancreatic duct due to pancreatitis and extravasation of the enzymatic material. Two thirds of patients with pseudocysts have demonstrable connections to the pancreatic duct. In the other third, an inflammatory reaction is supposed to have sealed the connection so that it is not demonstrable. The cause of pseudocysts parallels the cause of acute pancreatitis; 75-85% of cases are caused by alcohol or gallstone disease–related pancreatitis. In children, pseudocysts and trauma are frequently associated.

Sex- and age-related demographics

The male predominance in the incidence of pseudocysts mirrors the male predominance in the incidence of pancreatitis.

Pseudocysts may occur after pancreatitis in any age group. In children, pseudocysts are most likely observed after abdominal trauma. In elderly persons, care should be taken not to confuse cystic neoplasms with pseudocysts.

Most pseudocysts resolve without interference, and patients do well without intervention. The outcome is much worse for patients who develop complications or who have the cyst drained. The presence of pancreatic necrosis is a poor prognostic sign.

The failure rate for drainage procedures is about 10%, the recurrence rate is about 15%, and the complication rate is 15-20%.

Complications

Bleeding is the most feared complication and is caused by the erosion of the pseudocyst into a vessel. Consider the possibility of bleeding in any patient who has a sudden increase in abdominal pain coupled with a drop in hematocrit level or a change in vital signs. Therapy is emergent surgery or angiography with embolization of the bleeding vessel.

Do not perform a percutaneous or endoscopic drainage procedure under any circumstances in patients with suspected bleeding into a pseudocyst. Consider the possibility of infection of the pseudocyst in patients who develop fever or an elevated WBC count. Treat infection with antibiotics and urgent drainage.

GI obstruction, manifesting as nausea and vomiting, is an indication for drainage.

The pseudocyst can also rupture. A controlled rupture into an enteric organ occasionally causes GI bleeding. On rare occasions, a profound rupture into the peritoneal cavity causes peritonitis and death.

Patients who are being managed expectantly must be educated about the warning signs for potential complications (eg, abdominal pain, fever), which may indicate bleeding, infection, or pseudocyst rupture.

For patient education resources, see the Digestive Disorders Center, as well as Pancreatitis and Abdominal Pain in Adults.

No specific set of symptoms is pathognomic of pseudocysts; however, consider the possibility of a pseudocyst in a patient who has persistent abdominal pain, anorexia, or an abdominal mass after an episode of pancreatitis.

Rarely, patients present with jaundice or sepsis from an infected pseudocyst.

Pleural effusion is also a common finding.

The sensitivity of physical examination findings is limited. Patients very frequently have a tender abdomen. Patients occasionally have a palpable mass in the abdomen.

Peritoneal signs suggest rupture of the cyst or infection.

Other possible findings include the following:

• Fever

• Scleral icterus

• Pleural effusion

Bleeding is the most feared complication and is caused by the erosion of the pseudocyst into a vessel. Consider the possibility of bleeding in any patient who has a sudden increase in abdominal pain coupled with a drop in hematocrit level or a change in vital signs. Therapy is emergent surgery or angiography with embolization of the bleeding vessel.

Do not perform a percutaneous or endoscopic drainage procedure under any circumstances in patients with suspected bleeding into a pseudocyst.

Consider the possibility of infection of the pseudocyst in patients who develop fever or an elevated WBC count. Treat infection with antibiotics and urgent drainage.

GI obstruction, manifesting as nausea and vomiting, is an indication for drainage.

The pseudocyst can also rupture. A controlled rupture into an enteric organ occasionally causes GI bleeding. On rare occasions, a profound rupture into the peritoneal cavity causes peritonitis and death.

Serum tests have limited use. Amylase and lipase levels are often elevated but may be within the reference ranges. Bilirubin and liver function test (LFT) findings may be elevated if the biliary tree is involved.

Analysis of the cyst fluid may help differentiate pseudocysts from tumors. An attempt should be made to exclude tumors in any patient who does not have a clear history of pancreatitis. Note the following:

• Carcinoembryonic antigen (CEA) and carcinoembryonic antigen-125 (CEA-125) tumor marker levels are low in pseudocysts and elevated in tumors.

• Fluid viscosity is low in pseudocysts and elevated in tumors.

• Amylase levels are usually high in pseudocysts and low in tumors.

• Cytology is occasionally helpful in diagnosing tumors, but a negative result does not exclude tumors.

• A CEA level of greater than 400 ng/mL within the cyst fluid strongly suggests malignancy.

Abdominal ultrasonography

Abdominal ultrasonography may be used to visualize cystic fluid collections in and around the pancreas. However, the technique is limited by the operator’s skill, the patient's habitus, and any overlying bowel gas. As such, ultrasonography is not the study of choice to establish a diagnosis.

Endoscopic ultrasonography

Endoscopic ultrasonography (EUS) is not necessary to establish a diagnosis but is very important in planning therapy, particularly if endoscopic drainage is contemplated.

A gastric wall thickness greater than 1 cm next to the cyst tends to predict a poor outcome with endoscopic drainage.

EUS may also be helpful in detecting small portal collaterals from otherwise undetected portal hypertension that may increase bleeding risks with transmural drainage.

Transmural drainage may be performed only when a symptomatic pseudocyst is positioned next to the gut wall. See the image below.

Three views of a pancreatic pseudocyst noted during endoscopic ultrasound. The concentric rings in the center of the images are produced by the ultrasound transducer in the stomach. The cyst is observed as the large hypoechoic structure adjacent to the transducer.

Abdominal computed tomography (CT) scanning is the imaging criterion standard for pancreatic pseudocysts. It has a sensitivity of 90-100% and is not operator dependent. Note the following:

• The usual finding on CT scan is a large cyst cavity in and around the pancreas.

• Multiple cysts may be present.

• The pancreas may appear irregular or have calcifications.

• Pseudoaneurysms of the splenic artery, bleeding into a pseudocyst, biliary and enteric obstruction, and other complications may be noted on CT scan.

• The CT scan provides a very good appreciation of the wall thickness of the pseudocyst, which is useful in planning therapy.

Endoscopic retrograde cholangiopancreatography (ERCP) is not necessary in diagnosing pseudocysts; however, it is useful in planning drainage strategy.

A study by Neil et al investigated the use of ERCP and the treatment of pseudocysts and acute pancreatitis and reported that a change in management occurred 35% of the time after the ERCP findings in pseudocysts were evaluated. Therefore, many authors recommend performing an ERCP before contemplated drainage procedures.

Magnetic resonance imaging (MRI) is not necessary to establish a diagnosis of pseudocysts; however, it is useful in detecting a solid component in the cyst and in differentiating between organized necrosis and a pseudocyst.

A solid component makes catheter drainage difficult; therefore, in the setting of acute necrotizing pancreatitis with resultant pseudocyst, an MRI may be very important before a planned catheter drainage procedure.

Histologic findings vary with age because older cysts have thicker walls with more collagen. The etiology of the cyst does not change the histology. Note the following zone features:

• Zone 1 - Hemosiderin pigment and loose connective tissue

• Zone 2 - Inflammatory cells and capillary-rich fibrous tissue

• Zone 3 - Hyalinized acellular connective tissue

• Zone 4 - Capillary-rich fibrous stroma

The goal of therapy is avoidance of complications. Note the following:

• About 10% of pseudocysts become infected.

• Pseudocysts can also rupture. A controlled rupture into an enteric organ can sometimes cause GI bleeding. A free rupture into the peritoneal cavity produces abdominal pain and, rarely, peritonitis or even death.

• Most pseudocysts resolve without interference and only require supportive care.

• Several studies have indicated that the size of the cyst and the length of time the cyst has been present are poor predictors of complications. In general, larger cysts are more likely to become symptomatic or cause complications. However, some patients with larger collections do well; therefore, the size of the pseudocyst alone is not an indication for drainage.

Indications for drainage include the following:

• Complications

• Symptoms

• Concern about possible malignancy

Consultations

Management of pseudocysts requires a team approach. Gastroenterologists, surgeons, and invasive radiologists must work together to determine the necessity, timing, and method of intervention. If nonsurgical drainage is contemplated, it is important to elucidate the anatomy of the pancreatic duct beforehand. This may be done via endoscopic retrograde cholangiopancreatography (ERCP) or magnetic resonance imaging (MRI). A large number of patients who fail or have complications with nonsurgical drainage have disruption or stenosis of the pancreatic duct.

Diet and activity

Patients may eat a low-fat diet as tolerated. Patients in whom eating causes abdominal pain need parenteral or enteral nutrition through a percutaneously or endoscopically placed jejunal tube.

Patients may engage in activities as tolerated.

Outpatient monitoring

Patients who have endoscopically placed stents must be monitored via serial computed tomography (CT) scans to observe resolution of the cyst. Stents may then be endoscopically removed after resolution.

Closely monitor patients with percutaneous drains for pain, infection, or catheter migration. Remove the drain when drainage ceases.

Drainage options are outlined below.

Catheter drainage

Percutaneous aspiration is useful only to establish a diagnosis or as a temporizing measure. It has a 54% failure rate and a 63% recurrence rate. This technique has a relatively high risk of infecting the pseudocyst. Percutaneous drainage may have a higher complication rate and inpatient mortality rate than surgical drainage.

Percutaneous catheter drainage is the procedure of choice for treating infected pseudocysts, allowing for rapid drainage of the cyst and identification of any microbial organism. A high recurrence and failure rate exist, but catheter drainage may be a good temporizing measure.

Percutaneous catheter drainage is contraindicated in patients who are poorly compliant and cannot manage a catheter at home. It is also contraindicated in patients with strictures of the main pancreatic duct and in patients with cysts containing bloody or solid material.

Endoscopic drainage

Endoscopic drainage may be either transpapillary (via endoscopic retrograde cholangiopancreatography [ERCP]) or transmural. Both modalities require careful patient selection to ensure success and safety.

Transpapillary drainage

Transpapillary drainage, while safer and more effective than transmural drainage, requires cyst communication with the pancreatic duct. This technique may be technically challenging because it requires wire passage and stenting through the pancreatic duct to the pseudocyst. The success rate is about 80%. The recurrence rate is 10-14%, and, in most series, the complication rate (mainly pancreatitis) is approximately 13%.[4] See the image below.

These photographs show the endoscopic view of transpapillary pseudocyst drainage in a patient with pancreas divisum and a pseudocyst that communicates with the pancreatic duct. The image on the left shows the ampullary area. The middle image shows a wire placed in the minor papilla into the dorsal pancreatic duct. The right image shows a stent in place in the minor papilla.

Transmural drainage

Endoscopic transmural drainage is also possible.[5] This involves performing an endoscopy and finding a bulge into the lumen of the stomach or duodenum caused by compression of the pseudocyst. The cyst is generally entered using a needle knife to cut through the gastric or duodenum wall, and a series of pigtail stents are placed through the resulting communication. Some have adapted the technique to avoid diathermy, thus decreasing possible complications. The method has an 82-89% success rate in very experienced hands. The recurrent rate is 6-18%. The complication rate is 20%, with the most feared complication being bleeding.

One report suggested that the complication rate decreases and the efficacy increases with experience. Weckman reported an approximately 86% success rate with endoscopic drainage with a 10% complication rate and a 14% failure rate.[6] There appeared to be about a 15% recurrence rate. There was no real difference in outcome in patients treated with a transpapillary or transmural approach.

In December 2013, the FDA approved marketing of the AXIOS Stent and Delivery System for the treatment of pancreatic pseudocysts.[7] Approval of the stent, which creates a new temporary opening between the pancreas and the gastrointestinal tract, was based on a study of 33 patients with pancreatic pseudocysts at least 6 cm in diameter.[7] In this study, stents were successfully placed 90.9% of the time, 97% of the successfully implanted stents stayed in place for the duration of treatment, 93% of the stents remained open to allow drainage for the duration of treatment, and 86% of the treated pseudocysts decreased in size by at least 50%.[7]

Surgical drainage

Surgical drainage is the criterion standard against which all therapies are measured.

Internal drainage is the procedure of choice. A laparoscopic approach has been used in some cases with good results.[8]

In most series, the mortality rate is 3%, and the complication rate is approximately 24%. The success rate is 85-90%.

Relatively recent studies have suggested that a laparoscopic approach to drainage has a high success rate and a low morbidity rate.[9, 10]

No medications are specific to the treatment of pancreatic pseudocysts. Antibiotics are an adjunct to drainage of infected pseudocysts. Octreotide can be useful as an adjunct to catheter drainage.

Class Summary

Used to reduce pancreatic exocrine secretion.

Octreotide (Sandostatin)

Acts primarily on somatostatin receptor subtypes II and V. Inhibits growth hormone (GH) secretion and has a multitude of other endocrine and nonendocrine effects, including inhibition of glucagon, VIP, and GI peptides.