Pancreatic pseudocysts most commonly form in the setting of acute and chronic pancreatitis. The pathophysiology is key to understanding treatment strategy and options.
Acute pancreatitis is most often secondary to a gallstone or acute alcohol etiology. In this setting, the pancreatic duct is usually fairly normal and non-diseased before the inciting insult.
Accordingly, because the duct has minimal disruption other than the immediate injury, the damage to the duct that allowed pancreatic fluid to leak and form the pseudocyst is likely to heal spontaneously with a gradual resorption of the cyst fluid.
Almost universally in the setting of acute pancreatitis, experienced surgeons will adopt a period of watchful waiting in pancreatic pseudocysts before planning intervention. In fact, consensus guidelines do not even classify a pancreatic fluid collection as a pseudocyst unless a fibrous wall and fluid collection is present for 4 weeks.
In chronic pancreatitis, pseudocysts tend to be more symptomatic and cause abdominal pain, satiety, and a feeling of “fullness.”
Treatment strategies are multiple but all center on draining or surgically removing the cyst via invasive procedure. There is no medical treatment per se.
Cysts are drained using endoscopic techniques if possible. Procedures performed are transmural endoscopic drainage and transpapillary drainage.
Transmural drainage is appropriate if one of the walls of the pseudocyst abuts the stomach, duodenum, or small bowel. In this procedure, a needle is used to puncture the wall of the viscus and pseudocyst simultaneously, thus creating an internal drainage conduit for the cyst fluid. This technique is not used if there is infection present in the pseudocyst.
Transpapillary drainage requires the cyst to communicate or be in proximity to a pancreatic duct and uses the same puncture technique as in transmural drainage after the duct has been cannulated. A contraindication for this approach is extensive necrosis present in the pancreas or pseudocyst.
Pseudocysts can also be drained percutaneously, although the recurrence rate is 30% with this technique. This technique is particularly useful with large infected pseudocysts and in patients that are too ill to undergo endoscopy.
Although surgery has somewhat fallen out of favor, the most common surgical procedures used to drain pancreatic pseudocysts are cystgastrostomy, cystduodenostomy, and cystjejunostomy. For tail of pancreas collections, distal pancreatectomy has also been described.
Regardless of how the cyst is drained, a key treatment principle is fashioning dependent drainage of the pseudocyst fluid.
When diagnosing and treating pancreatic pseudocysts, care must be taken to differentiate them from both benign and malignant cystic neoplasms of the pancreas.
Cystic neoplasms are generally not seen in the setting of a previous bout of pancreatitis. However, the septa and calcium deposits sometimes seen in these lesions are not universally present and further work-up is needed.
Fine needle aspiration of pseudocyst is most consistent with a low carcinoembryonic antigen (CEA) level and a high CA 19-9. In addition, pseudocyst fluid contains a high level of amylase, low viscosity, the absence of mucin and the absence of cells or cellular debris.