Walled-off pancreatic necrosis (WON) is a defined entity that occurs following an episode of acute necrotizing pancreatitis. Direct endoscopic necrosectomy (DEN) is performed by advancing an endoscope transmurally into WON and has become an accepted modality. However, clinicians have many questions about endoscopic necrosectomy. Some of these questions will be addressed.
1. Is DEN required for all patients with WON?
No, not all patients with WON require endoscopic intervention. Careful patient selection of those who will benefit from DEN is crucial, because intervention carries risks of severe adverse events (AEs) and may not improve outcomes over supportive care. Once DEN is undertaken, one is then committed to seeing resolution of the now infected necrosis. Severe symptoms related to gastroduodenal obstruction, infection and continued systemic illness warrant intervention. In addition, placement of large-bore (15- to 20- mm diameter), lumen-apposing metal stents (LAMS) alone may allow complete drainage without the need for DEN. I perform upfront DEN in those patients with large cavities and in the presence of at least 40 percent solid debris as well as in those patients already hospitalized who are severely ill. I also perform DEN in those whose condition fails to improve following 20-mm LAMS placement alone.
2. Can DEN be performed safely at the time of initial transmural drainage?
Yes, but the LAMS must be balloon dilated to maximal stent diameter after deployment. There may be a higher risk of stent dislodgement during DEN performed at initial placement, although this is unproven.
3. Are LAMS required for necrosectomy?
No, but LAMS are useful because they allow for the rapid initial drainage of WON due to the one-step delivery system. They also provide easy access into the collection for DEN. When DEN is delayed and when repeat DEN is performed, reaccessing the necrotic cavity does not require tract dilation, which is almost universally required when plastic stents are used for transmural drainage.
4. Is DEN effective in the presence of large paracolic gutter collections?
The answer is a qualified maybe. Transmural drainage and DEN for WON are most effective for central collections. Although paracolic central necrosis collections usually communicate with the central necrosis, they are usually not effectively drained by only placing a stent in the central portion. An endoscope can be cautiously passed from the central portion into these peripheral collections, although it is often technically difficult and time and labor intensive.
5. Is it advisable to place plastic pigtail stents inside LAMS?
The answer is probably yes. Indeed, it is my preference, and it is supported by at least one study. There have been reports of severe, delayed bleeding following LAMS placement for WON. The precise mechanism for this is unknown, but it is believed to be due to impaction of the inner flange of the LAMS against the back wall of the collection as it collapses. I place a 10-Fr double pigtail stent through the LAMS lumen (7 Fr will migrate out of larger-diameter LAMS) at the time of the initial placement. This may also prevent occlusion of the LAMS by solid debris.
Transmural drainage and DEN for WON are most effective for central collections.
6. How often is DEN repeated?
We do not know. My approach depends on inpatient versus outpatient status. Inpatients, who are often severely ill and debilitated, are brought to the endoscopy suite every few days until their necrotic cavity is completely cleared of solid debris. Outpatients return every seven to 10 days depending on their clinical response and the amount of residual necrosis as based on endoscopic findings and, in some cases, cross-sectional imaging assessment.
7. How often is cross sectional imaging repeated once necrosectomy is initiated?
Early in my experience, repeat computed tomography (CT) was obtained weekly. However, patients with WON typically undergo repeat CT during their illness leading up to necrosectomy. In these often younger patients, concerns exist about their cumulative radiation exposure. The timing of my current approach depends on the degree of underlying solid debris and the presence of paracolic gutter collections. In patients with limited solid debris and no paracolic gutter collections, I place a LAMS and obtain CT or magnetic resonance imaging one month later. I obtain imaging earlier only if I am concerned about possible AEs or the patient’s condition has clinically worsening. In more complex collections, imaging is not repeated earlier than two-week intervals unless I am concerned about the potential for AEs or if the patient’s condition has clinically decompensated.
- Careful patient selection is required before undertaking endoscopic necrosectomy.
- Luminal-apposing metal stents may allow resolution of WON without direct necrosectomy when limited solid debris is present, and they may provide access when direct necrosectomy is performed.
- CT following necrosectomy should be obtained judiciously to reduce a patient’s cumulative exposure to radiation.
Dr. Baron has retainer agreements with Olympus, BSCI, Cook, Medtronic and W.L. Gore.