Pancreatic fluid collections (PFCs) are common after acute pancreatitis but almost always resolve spontaneously. Persistent collections that cause symptoms, become infected, and/or compress vital structures require treatment. Open surgery had traditionally been considered the standard method for this indication;1 Given its inherently less invasive nature, endoscopic transmural drainage (ETMD) has become a mainstay of this step-up philosophy – it is now the dominant strategy for pseudocyst drainage and, on the basis of emerging randomized trial data, compares very favorably with surgery for the treatment of walled-off necrosis (WON).
According to the step-up approach, the initial treatment of symptomatic and/or infected collections that are within 4 weeks of an attack of pancreatitis involves conservative management because the wall of the collection is typically immature; the systemic inflammation may be significantly exacerbated by definitive drainage, particularly surgery. In this early phase, failure of conservative management is addressed by percutaneous catheter placement, stepping up to a minimally invasive operation if the response to percutaneous drainage and antibiotics is insufficient.
Collections that are at least 4 weeks from the onset of acute pancreatitis are considered mature and termed pseudocysts or WONs depending on whether they contain pure fluid or necrotic tissue. In this phase, endoscopic treatment plays a primary management role because these collections are generally adherent to the stomach or duodenal wall and their capsule is organized enough to withstand endoscopic intervention. If treatment can be held off until this phase, then percutaneous and surgical drainage can often be avoided.
In practice, the 4-week rule holds true for most, but not all, PFCs. ETMD can be performed in some particularly mature collections prior to 4 weeks if the indication is strong and the collection appears to have a mature wall. However, the potential for cyst wall perforation is higher and should be considered in the risk-benefit discussion. Conversely, some collections beyond 4 weeks lack an adequately organized wall and require additional time for maturation.
While endoscopic drainage of pseudocysts has essentially supplanted surgery, the management of WON is more complex and remains multidisciplinary. Two recent randomized trials demonstrated no difference in major complications and/or death between a surgical and endoscopic step-up strategy for WON.2,3 Rates of pancreatic fistulae, hospital stay, and overall treatment costs, however, favored endoscopy. Nevertheless, defining the ideal strategy for many of these patients with complexity requires multidisciplinary discussion. Surgery continues to play a primary role in several scenarios, including collections that are not close to the upper GI tract, those that are particularly complex and extend caudally, and situations in which the endoscopic progress is too slow.
The three most important questions when deciding to embark on ETMD are: (1) whether drainage is indicated (that is, is the patient symptomatic or is there evidence that the PFC is infected?), (2) whether the wall of the collection is adequately mature and apposed to the GI tract wall; and (3) whether the collection contains necrosis? This last question has critical implications in the technical approach to drainage. While CT scan with IV contrast is accurate for assessing wall maturity, it is inadequate to evaluate the presence or quantity of necrosum. Transabdominal ultrasound, endoscopic ultrasound, and MRI (on a T2 sequence) are all superior for this purpose. MRI has the additional benefit of assessing the pancreatic duct integrity, which may influence subsequent management.