ERCP and EUS Procedures: ERCP and EUS Procedures: Walled-Off Necrosis

0:00Welcome to Board Pearls. This is episode six of seven of the ERCP and EUS Procedures chapter, in the Endoscopic Procedures module. This episode is walled-off necrosis, drained through the stomach and cleaned out from the inside. The first patient is a woman six weeks after necrotizing pancreatitis, and her case shows when a collection is ready to drain and what has to be checked first, which stent suits necrosis, when she needs necrosectomy and why the gas must be carbon dioxide, what recurrent fever and bleeding through the stent each mean, and when the stent comes out. A man with a simple pseudocyst shows which stent suits thin fluid. And a woman with a cyst in her pancreatic tail shows a cyst that only looks like a pseudocyst.

0:42Here's the patient. A fifty-seven-year-old woman had severe necrotizing pancreatitis from alcohol six weeks ago. For two weeks she's had a low-grade fever and early fullness. Her white count is sixteen thousand. Her computed tomography, CT, shows a fourteen-centimeter collection in her lesser sac with a thick, enhancing wall, heterogeneous contents, and areas of solid debris, lying against the back wall of her stomach. Her team has started antibiotics for suspected infected necrosis.

1:13She has symptomatic, probably infected, walled-off pancreatic necrosis: a heterogeneous collection containing solid debris with a mature wall after four weeks, classically following necrotizing pancreatitis. A pseudocyst, by contrast, is a homogeneous fluid collection with a mature wall after four weeks and no significant solid debris. Her thick wall, solid debris, and timing after necrotizing pancreatitis make hers walled-off necrosis. Symptomatic collections at four weeks or later are managed by endoscopic ultrasound, EUS, guided transmural drainage, because the inflammatory rind needs that time to mature into a wall that can support an opening into the gut without leaking. At six weeks with a thick wall, she's ready to drain.

2:00Her drainage follows a step-up approach: the less invasive intervention first, and the more invasive one only if the first fails. For her, that means transmural drainage first, with necrosectomy only if she doesn't respond. That principle was established for surgery and is supported for the endoscopic approach by randomized trials.

2:21Her vessels are checked before any needle goes in. CT angiography or contrast-enhanced imaging is reviewed to exclude a pseudoaneurysm in the cavity wall or in the splenic, gastroduodenal, or pancreaticoduodenal arteries. Pseudoaneurysm is a feared complication of necrotizing pancreatitis, caused by enzymes eroding arterial walls, and puncturing a cavity that contains one or shares a wall with one can cause uncontrolled hemorrhage. If a pseudoaneurysm is found, interventional radiology embolizes it before drainage. Hers shows none.

2:55Her solid debris decides her stent. Walled-off necrosis needs a larger-caliber lumen-apposing metal stent, LAMS, because solid debris can't pass through a small stent, and the stent has to be wide enough for an endoscope to pass through if necrosectomy is needed. Fifteen- and twenty-millimeter LAMS give room for the scope and reduce the need for balloon dilation, so they're preferred for walled-off necrosis. With visible solid debris, she gets a twenty-millimeter LAMS from her stomach into the cavity.

3:24A simple pseudocyst needs much less, and a second patient shows the contrast. A fifty-year-old man has a seven-centimeter homogeneous pseudocyst causing early satiety eight weeks after mild gallstone pancreatitis. Thin fluid with little debris drains well through a single ten-millimeter LAMS or through two double-pigtail plastic stents, because the contents flow easily through a small lumen, and plastic stents are a reasonable lower-cost choice when a LAMS isn't available or affordable. In her cavity, those small stents would block with debris and leave no way in for a scope.

4:01Her first week after drainage shows whether drainage alone is enough. Necrosectomy is reserved for an inadequate response, meaning persistent fever, persistent leukocytosis, or persistent solid debris on imaging. At one week she still has a fever of thirty-eight point six, a white count of fifteen thousand, and a cavity that's barely smaller and full of debris, so her response is inadequate.

4:25She needs direct endoscopic necrosectomy, debridement of the cavity through the LAMS. It's now the standard for persistent solid debris in walled-off necrosis and has replaced surgical necrosectomy in most patients, because the approach through the stomach wall crosses neither the peritoneum nor the retroperitoneum, avoiding the fistulas, prolonged ileus, and wound infections that drive the morbidity of surgery. A forward-viewing therapeutic endoscope passes through the LAMS into the cavity, and snares, baskets, nets, and forceps remove the necrotic tissue. Each session clears part of the cavity, and several sessions are usually needed, a median of two to four, with two to six reported, because the necrotic tissue is adherent and removing it all at once risks bleeding from the granulation tissue beneath. Dilute hydrogen peroxide, typically three percent, is sometimes used to loosen adherent debris, but the practice isn't universal.

5:23Her necrosectomy uses carbon dioxide, never air, because of where the cavity may lead. The cavity may communicate with blood vessels or the peritoneum, and air insufflated into it risks air embolism through the splenic vein or portal venous branches. Carbon dioxide is rapidly absorbed and causes no clinical embolism even if some enters a vessel. Forceful pressurized flushing is avoided for the same reason, because pressurizing the cavity can drive gas or fluid into a vascular communication.

5:53Her care between sessions keeps the cavity draining and watches for its complications. Her LAMS stays in place for drainage, her broad-spectrum antibiotics continue because her necrosis is infected, and a nasogastric tube would decompress persistent ileus. The complications of necrosectomy are bleeding from granulation tissue or a wall pseudoaneurysm, perforation of the cavity wall into the peritoneum, reinfection of the cavity from gut flora through the LAMS, which is treated with antibiotics and adequate drainage, and the rare air embolism that carbon dioxide prevents. She has three sessions over two weeks, and her fever settles as the cavity shrinks.

6:30If her fever had come back after improving, the stent itself would be the first suspect. Recurrent fever and rising inflammatory markers despite drainage suggest LAMS occlusion by retained necrotic material. That's treated with urgent esophagogastroduodenoscopy to clear the stent lumen, and double-pigtail plastic stents are placed through the LAMS, which keep a smaller channel open even as debris builds up around them.

6:56If she'd bled through the stent instead, the order of steps would matter more than anything else. Melena, hematemesis, or shock through the stent means bleeding into the tract, usually from a pseudoaneurysm. It's treated with interventional radiology embolization before the LAMS is removed, because the stent may be tamponading the vessel, and taking it out first can release that tamponade and cause uncontrolled hemorrhage. So in both places, before drainage and after it, a pseudoaneurysm goes to radiology before anyone opens or closes the cavity.

7:26Her LAMS has a planned exit. It's reassessed and typically removed at about four weeks, with four to eight weeks as the broader acceptable range, once the cavity has resolved clinically and on imaging. Earlier removal lets the tract collapse before the cavity has fully drained. The stent's recognized complications are delayed bleeding, often from a pseudoaneurysm, buried LAMS syndrome, and migration, and removal is timed by clinical and imaging resolution rather than a fixed date. After removal, double-pigtail plastic stents are placed across the now-mature tract for extended internal drainage. Her cavity has collapsed on CT at five weeks, her LAMS is removed, and two pigtail stents are placed.

8:08Not every collection after pancreatitis is what it seems, and a third patient shows why. A forty-six-year-old woman has a cyst in her pancreatic tail that persists after an episode of acute pancreatitis, and it's unclear whether it communicates with the duct. It's aspirated before any drainage, because a mucinous cystic neoplasm or a branch-duct intraductal papillary mucinous neoplasm can masquerade as a pseudocyst. Cyst fluid carcinoembryonic antigen, glucose, amylase, and molecular markers settle the question, as chapter twenty-six covers. Draining a mucinous neoplasm as if it were a pseudocyst treats the wrong disease.

8:48Here are the traps the boards set in these patients. A collection isn't drained before about four weeks, when the wall has matured. Imaging is checked for a pseudoaneurysm before any drainage, and one that's found is embolized first. Walled-off necrosis needs a fifteen- or twenty-millimeter LAMS, not a ten-millimeter LAMS or plastic stents. Drainage comes first, and necrosectomy only after an inadequate response. Necrosectomy uses carbon dioxide, never air, and no forceful flushing. One necrosectomy session usually isn't enough. Recurrent fever after drainage means clearing an occluded LAMS, not antibiotics alone. A bleeding pseudoaneurysm is embolized before the LAMS is removed. A LAMS isn't left in indefinitely. And a persistent tail cyst is aspirated to exclude a mucinous neoplasm before it's drained.

9:43So, start to finish. Drain symptomatic collections after about four weeks, once they're walled off, and exclude a pseudoaneurysm on imaging first, embolizing it if present. Drain pseudocysts with a ten-millimeter LAMS or two double-pigtail stents, and walled-off necrosis with a fifteen- or twenty-millimeter LAMS. Add direct endoscopic necrosectomy only if fever, leukocytosis, or debris persists, expecting two to four sessions, always with carbon dioxide and without forceful flushing.

10:14Recurrent fever means an occluded LAMS, which is cleared with pigtail stents placed through it. Bleeding into the tract means embolization before the LAMS comes out. Remove the LAMS at about four weeks once the cavity has resolved, and place pigtail stents across the tract. And aspirate a persistent tail cyst before draining it.

10:33Episode seven is EUS tissue acquisition, celiac plexus neurolysis, endoscopic retrograde cholangiopancreatography, ERCP, in pregnancy, complications, and duodenoscope reprocessing.

10:47For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode six of seven of chapter twenty-nine, and I'll see you in the next one.