Cystic Diseases

A. Pancreatic pseudocysts

It is important to distinguish pseudocysts from tumors and other fluid collections. An acute pancreatic fluid collection follows in approximately 25% of patients with acute pancreatitis. It is characterized by acute inflammation, cloudy fluid, a poorly defined cyst wall, and necrotic but sterile debris. This may resolve spontaneously, and in fact most “pseudocysts” that resolve are likely of this type. By definition, a fluid collection in the first 4 weeks is an acute fluid collection; after 4 weeks, it becomes an acute pseudocyst.

• Causes. Pseudocysts develop after disruption of the pancreatic duct with or without proximal obstruction; they usually occur after an episode of acute pancreatitis. In children, most pseudocysts arise as a complication of blunt abdominal trauma.

• Diagnosis

1. Clinical presentation. The most common complaint is recurrent or persistent upper abdominal pain. Other symptoms include nausea, vomiting, early satiety, anorexia, weight loss, and jaundice. Physical examination is significant for upper abdominal tenderness and occasionally reveals an abdominal mass.

2.  Laboratory tests

• Amylase. Serum concentrations are elevated in approximately one half of cases.

• Liver function tests occasionally are elevated and therefore are not of diagnostic use.

• Cystic fluid analysis is discussed in Section V.B.2.

3.  Radiologic studies

• CT is the radiographic study of choice for initial evaluation of pancreatic pseudocysts and is twice as sensitive as ultrasonography in detection of pseudocysts. CT scan findings that determine prognosis include the following:

Pseudocysts smaller than 4 cm usually resolve spontaneously.

Pseudocysts with wall calcifications generally do not resolve.

Pseudocysts with thick walls are resistant to spontaneous resolutio

•  Ultrasonography detects approximately 85% of pseudocysts. Its use is limited by obesity and bowel gases, but it may be used in follow-up studies once a pseudocyst has been identified by CT scan.

4. ERCP allows for the determination of pancreatic duct anatomy and   influences therapeutic intervention. Approximately one half of pseudocysts have ductal abnormalities identified by ERCP, such as proximal obstruction, stricture, or communications with the pseudocyst. ERCP itself risks superinfection of a communicating pseudocyst.

• Complications

1.Infection is reported in 5% to 20% of pseudocysts and requires external drainage.

2.Hemorrhage results from erosion into surrounding visceral vessels and occurs in approximately 7% of cases. The most common arteries are the splenic (45%), gastroduodenal (18%), and pancreaticoduodenal (18%) arteries. Immediate angiography has emerged as the initial treatment of choice.

3.Obstruction. Compression can occur anywhere from the stomach to the colon. The arteriovenous system also can be subject to compression, including the vena caval and portal venous system. Hydronephrosis can result from obstruction of the ureters. Biliary obstruction can present as jaundice, cholangitis, and biliary cirrhosis.

4.Rupture occurs in fewer than 3% of cases. Approximately one half of patients can be treated nonsurgically, with total parenteral nutrition and symptomatic paracentesis or thoracentesis. Rupture is occasionally associated with severe abdominal pain and presents as a surgical emergency.

• Treatment depends on symptoms, age, pseudocyst size, and the presence of complications. for less than Pseudocysts smaller than 6 cm and present 6 weeks have low complication rates. The chance of spontaneous resolution after 6 weeks is low, and the risk of complications rises significantly after 6 weeks.

1.Nonoperative. If the pseudocyst is new, asymptomatic, and without complications, the patient can be followed with serial CT scans or ultrasonography to evaluate size and maturation of the pseudocyst. The majority of pseudocysts larger than 6 cm require surgery.

2.Percutaneous drainage can be considered for patients in whom the pseudocyst does not communicate with the pancreatic duct and for those who cannot tolerate surgery. External drainage is indicated when the pseudocyst is infected and without a mature wall. Simple aspiration is the least effective of the percutaneous interventions. The duration of drainage ranges from several days to several months (usually 3 to 4 weeks). The results are variable, and the rate of complications (e.g., fistulas) may be high.

3.Excision may be necessary in patients with symptomatic immature pseudocysts associated with complications or in those with mature distal pancreatic pseudocysts. Resection can require a Whipple procedure (pancreaticoduodenectomy) for pseudocysts at the head of the pancreas (rarely indicated) or distal pancreatectomy for pseudocysts in the body or tail of the pancreas.

4.Internal drainage. Cystoenteric drainage is the procedure of choice in uncomplicated pseudocysts requiring surgical treatment. Options include Roux-en-Y cystojejunostomy, loop cystojejunostomy, cystogastrostomy, and cystoduodenostomy. A biopsy of the cyst wall should be obtained to rule out cystic neoplasm. The recurrence rate after these procedures is approximately 10%. Endoscopic cystogastrostomy or cystoenterostomy has been performed in some centers. There is an increased risk of perforation with this procedure and an increased risk of recurrence due to inadequate drainage. At our institution, we favor the Roux-en-Y cystojejunostomy or cystogastrostomy in most patients.

B. True pancreatic cysts

1.Histopathologic classification. Although several different histologic types of cystic pancreatic neoplasms (CPNs) have been described, the following are most common..

•  Serous cystadenoma are benign lesions and are usually asymptomatic. They are more common in women (65%), are located in the head of the pancreas, and account for 30% of all CPNs.

• Mucinous cystic neoplasms (MCNs) are considered premalignant lesions and account for 35% of all CPNs. At presentation they can be symptomatic, are twice as likely to present in women, and anatomically are more commonly located in the body or tail. The cystic lesions do not communicate with the pancreatic ductal system.

• Intraductal papillary mucinous tumors (IPMTs) account for 25% of all CPNs and have a slight male predominance. They can be symptomatic and do communicate with the pancreatitic ductal system. IPMTs carry a very high malignant potential, up to 40% in some series. They are more commonly located in the head of the pancreas and can involve the ampulla of Vater.

• Other rare cystic pancreatic neoplasms (remaining 10%) include cystadenocarcinoma, acinar cell cystadenocarcinoma, cystic choriocarcinoma, cystic teratoma, and angiomatous neoplasms.

2.When a cystic pancreatic lesion has been identified by imaging, cyst fluid analysis is an essential part of the diagnostic workup. The most important finding is the presence of mucin. During ERCP, mucin egress from the bulging papilla can be highly suggestive of IPMT. If mucin is present on ERCP or cyst fluid analysis, the lesions is either premalignant or malignant and therefore requires resection. Analysis for the following may also prove useful:

• Carcinoembryonic antigen is elevated in both MCNs and IPMTs but most markedly in MCNs. It is low in serous cysts and pseudocysts.

• CA 19-9 can be elevated in malignant cyst neoplasms.

• CA 72-4 is low in pseudocysts and serous tumors. Levels are elevated in benign mucinous cystadenomas and very high in the setting of cystic malignancy.

• Amylase and lipase generally are high in pseudocysts and low in cystic tumors.

• Fluid viscosity is elevated in mucinous tumors and low in pseudocysts and serous cystic tumors.

• Percutaneous cytology is useful in determining malignant tumors but limited in discriminating between pseudocysts and serous cystadenoma.

• Percutaneous wall biopsy allows for discrimination between pseudocysts (which lack epithelial lining) and cystic neoplasms. It also can discriminate between serous (cuboidal epithelium) and mucinous (tall columnar epithelium and goblet cells). However, neoplastic cysts may have areas of cyst wall denuded of epithelium, which mimic pseudocysts.

3.Treatment

• Serous cystic neoplasms are benign lesions for which radiographic observation is sufficient. Indications for operative management are lesions that are symptomatic or distal disease for which there is some diagnostic uncertainty.

• Mucinous cystic neoplasms have malignant potential, and therefore surgical resection is warranted. However, lesions less than 2 cm in size rarely have malignant foci and can be followed. With curative resection, patients with mucinous cystadenocarcinoma have 5-year survival rates over 95%.

• IPMT warrants resection. The type of resection is dictated by the anatomic location of the lesion and its relation to the pancreatic ductal system. So-called “branched duct disease,” typically involving the head, requires a localized resection, most commonly a pylorus-sparing Whipple procedure. However, in “main duct disease,” the process can be either localized or multifocal. Traditionally, the approach to this disease pattern was to perform a distal pancreatectomy with immediate frozen-section analysis of the proximal ductal margin. More recently, a consensus statement established that histologic interpretation of frozen section margins is not as straightforward as had been previously believed. IPMT requires long-term follow-up and carries a 75% 5-year survival rate.