Excerpt from Pancreatic Pseudocysts

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Background

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 questions of when and whether drainage should be performed and what modality should be used to drain the cysts are often asked. 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.

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

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, organized necrosis is actually devitalized pancreatic tissue that appears cystlike on CT scan, but it appears to be solid on other imaging modalities. Second, an abscess is an infected area of necrosis or fluid.

Pathophysiology

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 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

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

Age

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

Please click here to view the full topic text: Pancreatic Pseudocysts