ACR Codes: 7.2
Pancreatic pseudocysts are non-epithelial lined cystic fluid collections that arise from disruption of a pancreatic duct, with leakage of amylase-rich pancreatic juice into the surrounding peripancreatic tissues. Pancreatic pseudocysts are one of four cystic lesions of the pancreas but accounts for 75% of all pancreatic cysts. The other three lesions include 1) benign and malignant cystic neoplasms (10%), 2) congenital cysts (5%), and 3) retention cysts (10%). Although pancreatic pseudocysts are the most common cystic lesion, neoplastic cysts must always be considered, particularly when contemplating nonsurgical treatment of a pancreatic cyst, since no diagnostic test or method is definitive or sensitive enough to distinguish the two.
-Etiology and Pathogenesis:
Pseudocysts form after rupture of a pancreatic duct with extravasation of amylase-rich fluid and failure of reabsorption of this secretion. The extravasated fluid forms an encapsulated collection that is bound by surrounding viscera, that is, the stomach, spleen, liver, and transverse mesocolon. The fluid collections initially communicate with the ruptured pancreatic duct. Endoscopic studies have shown that pancreatic pseudocysts communicate with the pancreatic duct in 80% of cases. Pseudocysts are preceded by pancreatitis in 90% of cases and by trauma in 10%. Approximately 85% are located in the body or tail of the pancreas and 15% in the head. Some patients have two or more pseudocysts. Abdominal pain, with or without radiation to the back, is the usual presenting complaint. A palpable, tender mass may be found in the middle or left upper abdomen. The serum amylase level is elevated in 75% of patients at some point during their illness and may fluctuate markedly
-Epidemiology:
Axial imaging in acute pancreatitis has demonstrated peripancreatic fluid collections in as many as 80% of studies. Pseudocysts occur less frequently than do acute fluid collections and require more time to form with prevalence ranging from 5% to 70% depending on the severity of the attack and the depth of investigation. There is no gender preference.
-Clinical Manifestations:
Pseudocysts usually require at least 4 or more weeks to evolve, following an episode of acute pancreatitis. However, the natural history and clinical relevance of pancreatic pseudocysts have been challenging due to lack of unified methods of dectection. Cysts have indeterminate age and most are stable on follow-up examinations. Symptomatic cysts may manifest as persistent abdominal pain with or without radiating to back, abdominal mass, gastric outlet obstruction, and biliary obstruction. Infection is suspected in septic patients and, unless air bubbles produced gas-forming bacteria are present, the diagnosis should be confirmed with FNA. A pseudocyst that does not resolve spontaneously may lead to serious complications, such as (1) pain caused by expansion of the lesion and pressure on other viscera, (2) rupture, (3) hemorrhage, and (4) abscess. Rupture of a pancreatic pseudocyst is a particularly serious complication. Shock almost always supervenes. Mortality rates range from 14%, if the rupture is not associated with hemorrhage, to over 60% if hemorrhage has occurred. Rupture and hemorrhage are the prime causes of death from pancreatic pseudocyst. A triad of findings: (1) increase in the size of the mass, (2) a localized bruit over the mass, and (3) a sudden decrease in hemoglobin level and hematocrit without obvious external blood loss, should alert one to the possibility of hemorrhage from a pseudocyst.
-Treatment:
In studies with sonography, pseudocysts were seen to resolve in 25 to 40% of patients. Pseudocysts that are greater than 5 cm in diameter and that persist for longer than 6 weeks should be considered for drainage. Recent natural history studies have suggested that noninterventional, expectant management is the best course in selected patients with minimal symptoms and no evidence of active alcohol use in whom the pseudocyst appears mature by radiography and does not resemble a cystic neoplasm. A significant number of these pseudocysts resolve spontaneously more than 6 weeks after their formation. Also, these studies demonstrate that large pseudocyst size is not an absolute indication for interventional therapy and that many peripancreatic fluid collections detected on CT in cases of acute pancreatitis resolve spontaneously. In patients who are stable and free of complications, and in whom serial ultrasound studies show that the pseudocyst is shrinking, conservative therapy is indicated. Conversely, if the pseudocyst is expanding and is complicated by rupture, hemorrhage, or abscess, the patient should be operated on. With ultrasound or CT guidance, sterile chronic pseudocysts can be treated safely with single or repeated needle aspiration or more prolonged catheter drainage with a success rate of 45 to 75%. The success rate of these techniques for infected pseudocysts is considerably less (40 to 50%). Patients who do not respond to drainage require surgical therapy for internal or external drainage of the cyst.
Reference(s): 1. Avram M. Cooperman. An overview of Pancreatic Pseudocysts. Surgical Clinics of North America, volume 81, number 2, April 2001
2. Balthazar, Emil J. Complications of acute pancreatitis: clinical and CT evaluation. Radiologic Clinics of North America, volume 40, number 6, December 2002
3. Harrison's Principles of Internal Medicine, 15th edition
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