Percutaneous Interventions and Necrosectomy in the Management of Peripancreatic Collections

Abstract

Acute pancreatitis (AP) is a severe inflammatory condition of the pancreas with significant morbidity and mortality, particularly in its necrotizing form. This review explores the management of peripancreatic collections and in particular necrotizing pancreatitis, focusing on the evolution from traditional open surgical methods to contemporary minimally invasive image-guided techniques. AP can lead to various local complications, including pancreatic pseudocysts, acute necrotic collections, and walled-off necrosis. Imaging plays a crucial role in diagnosing complications of AP, while treatment approaches have shifted toward a step-up strategy involving percutaneous, endoscopic, and minimally invasive methods. Percutaneous necrosectomy, combining mechanical and chemical debridement, has shown promising results. Mechanical necrosectomy uses devices like baskets and retrieval nets, while chemical necrosectomy adds agents like hydrogen peroxide and streptokinase. Current evidence suggests that the step-up approach, starting with percutaneous drainage or necrosectomy and escalating to endoscopic or surgical interventions, if necessary, improves patient outcomes. The review underscores the need for a multidisciplinary approach in managing complicated AP and highlights ongoing advancements in minimally invasive techniques.

Acute pancreatitis (AP) is characterized by the abrupt onset of pancreatic inflammation with rapid emergence of symptoms. Without necrotic damage to the gland, this condition can be resolved after addressing the underlying causes, such as gallstones, alcohol, hypertriglyceridemia, or hypercalcemia. According to the latest data, AP causes more than 285,000 annual hospital admissions and has a mortality rate of 1.0 per 100,000 patients in the United States. ¹ However, patients with severe AP, defined as the presence of persistent (≥ 48 hours) organ failure, experience much higher mortality rates. AP can cause local pancreatic complications, including pancreatic pseudocyst (PP), acute peripancreatic fluid collection (APFC), acute necrotic collection (ANC), walled-off necrosis (WON), and infected necrosis, as well as other local complications such as gastric outlet dysfunction, colonic necrosis, and portal and splenic vein thrombosis. ² These local complications can be detected by early and late medical imaging. About 5 to 15% of AP patients develop necrotizing pancreatitis, which causes organ failure in nearly half of these patients and increases the mortality rate. ³

Managing complicated pancreatitis is a challenging process that includes various treatment techniques such as fluid resuscitation, oxygen therapy, analgesia, antibiotics, proper nutrition, and drainage of fluid and necrotic collections percutaneously, endoscopically, or by open necrosectomy. ^{4 5} Surgical treatments of necrosis include open necrosectomy, minimal access retroperitoneal pancreatic necrosectomy, endoscopic transgastric necrosectomy, video-assisted retroperitoneal debridement, and image-guided, minimally invasive percutaneous necrosectomy. ⁶ The management of acute necrotizing pancreatitis has evolved from open surgical intervention, which had high mortality and morbidity rates, to minimally invasive techniques as the first-line interventions. Although interventional radiologists were historically involved in the management of complications of open necrosectomy, mainly hemorrhage, in recent years they have gained a more prominent role in the step-up treatment of pancreatic necrotic collections. ⁷ The current approach involves a multimodal technique that includes surgery, upper endoscopy, percutaneous image-guided interventions, and nutrition as the mainstays. ⁸

This review provides an overview of the management of peripancreatic fluid collection. It aims to discuss the current indications, techniques, and outcomes of minimally invasive percutaneous necrosectomy and explore future trends and perspectives in this rapidly evolving field.

Categorization of Peripancreatic Collections

The 1992 Atlanta classification, and its subsequent iterations, is a system used to categorize the severity and complications of AP. According to this system, and based on early cross-sectional imaging findings, collections of AP are divided into four types based on the contents and acuity of collections: APFC, PP, ANC, and WON ( Table 1 ). ^{9 10} While APFC and PP occur in interstitial edematous pancreatitis constructed of homogenous fluid, ANC and WON occur in necrotizing pancreatitis including fluid intermixed with necrotic tissues. The main difference between APFC and PP, as well as ANC and WON, is that WON and PP are surrounded by a capsule that usually forms 4 weeks after the beginning of pancreatitis symptoms. ¹¹ Typically, most APFCs do not become infected and resolve spontaneously; however, some may persist and evolve into PPs. ¹² The primary cause of APFCs and PPs is generally attributed to the damage or disruption of the pancreatic duct or one of its intrapancreatic branches. Nonetheless, direct communication with the pancreatic duct is not a prerequisite, as these conditions can also arise from local edema induced by pancreatic inflammation. ¹³ ANC may also be linked to damage to the main pancreatic duct within the area of parenchymal necrosis; however, both ANC and WON (necroma) can derive from necrosis in pancreatic parenchyma or peripancreatic tissues and can be infected. Approximately one-third of these necrotic collections become infected, which causes the mortality rate to almost double to nearly 30%. ^{11 14} Also, these collections may lead to gastric outlet obstruction because of their mass effect. ¹⁵

Table 1. Pancreatic collection characteristics.

Pancreatitis and collection type	Time after onset	Location	Imaging features in CT and CECT
IEP
APFC	≤4	Extrapancreatic	Homogenous appearance with decreased (fluid) density without a definable wall
PP	≥4	Usually extrapancreatic	Homogenous appearance with decreased (fluid) density and enhancing round or oval wall
NP
ANC	≤4	Intra- and/or extrapancreatic	Heterogeneous appearance due to non-liquid components without a definable wall; the presence of fat density in collection due to necrotic components in unenhanced CT
WON	≥4	Intra- and/or extrapancreatic	Heterogeneous appearance due to non-liquid components with a well-defined wall; the presence of fat density in collection due to necrotic components in unenhanced CT

Abbreviations: ANC, acute necrotic collection; APFC, acute peripancreatic fluid collection; CECT, contrast-enhanced computed tomography; CT, computed tomography; IEP, interstitial edematous pancreatitis; NP, necrotizing pancreatitis; PP, pancreatic pseudocyst; WON, walled-off necrosis.

APFCs typically present with a homogeneous appearance and decreased density on contrast-enhanced computed tomography (CECT; Table 1 ). They are commonly observed within the interior pararenal space and lesser sac and may be multiple. PPs exhibit similar imaging characteristics, but with the distinguishing feature of enhancing round or oval capsules on CECT. Both APFCs and PPs are extrapancreatic and generally resolve without intervention. However, persistent PPs are associated with clinical symptoms and an increased risk of complications, including infection, mass effects, rupture, and bleeding. ¹⁶

Despite the presence of previous collections, ANCs and WON can be either extra- or intrapancreatic and exhibit a heterogeneous appearance on CECT due to the presence of necrotic tissue. ¹⁷ A well-defined capsule is a key distinguishing feature of WON compared with ANCs. If a collection appears homogeneous but is associated with pancreatic parenchymal necrosis, it is classified as an ANC. Imaging is ideally conducted 5 days after the onset of the disease, as necrosis typically does not develop during the initial days. ANC and APFCs can be differentiated on unenhanced CT by the presence of fat density within the pancreatic collection, indicative of necrosis. However, ultrasound or MRI may be necessary to distinguish between WON and PPs by detecting necrotic debris. ^{13 16} Figs. 1 and 2 present various imaging findings of lesions with varying severity based on the revised Atlanta classification.

Fig. 1.

A patient with alcoholic pancreatitis. ( a ) Acute interstitial pancreatitis with associated peripancreatic fluid (arrows) representing an acute pancreatic fluid collection (APFC), defined as a simple-appearing non-loculated fluid collection, < 4 weeks from presentation). ( b ) Follow-up imaging performed 7 weeks later shows well-defined fluid collection along the pancreatic tail with no associated complexity (arrow), representing a pseudocyst which is defined as an encapsulated peripancreatic or remote, simple-appearing fluid collection that develops after 4 weeks. Notice the lack of internal complexity of the fluid collection. Another patient with alcohol-induced pancreatitis. ( c ) Initial images show heterogeneous enhancement of the pancreas with stranding around the pancreas and in the left anterior pararenal space (arrow). Findings represent acute interstitial pancreatitis with small APFC, defined as a simple-appearing, non-encapsulated peripancreatic fluid in the first 4 weeks of presentation. After 4 weeks, this is called a pseudocyst, and often has a more encapsulated appearance, and may be more remote in its location. ( d ) Within 1 week of presentation, diffuse heterogeneous regions of pancreatic devascularization are called acute necrotic collection. Complex fluid seen in the lesser sac in the setting of necrotizing pancreatitis also represents acute necrotic collection (arrows). ( e ) Approximately 5 weeks after presentation, a loculated heterogeneous fluid collection is seen throughout the pancreas with small foci of fat attenuation consistent with fat necrosis (arrows). Similar fluid collections are seen in the lesser sac and left anterior pararenal space. These are called walled-off necrosis and are defined as a fluid collection associated with necrotizing pancreatitis that develops after 4 weeks.

Fig. 2.

A patient with gallstone-related pancreatitis. ( a ) At presentation, there are areas of deep devascularization of the proximal pancreatic body (arrow) called acute necrotic collection (ANC). ( b ) Five days after presentation: extensive peripancreatic stranding and heterogeneous fluid extending into the transverse mesocolon associated with regions of fat necrosis (arrows), at this point called an acute necrotic collection. ( c ) Five weeks later, a lobulated loculated fluid collection is seen in the middle pancreatic body with internal debris (arrow) representing walled-off necrosis (WON). MRI was performed immediately after this CT. ( d ) T2-weighted MRI 5 weeks after presentation demonstrates a heterogeneous signal intensity within the fluid collection centered in the pancreatic body (arrow), consistent with walled-off necrosis. Internal complexity in walled-off necrosis is often better seen on MRI. ( e ) T1-weighted fat saturated precontrast MRI: heterogeneous proteinaceous signal intensity is identified in the dependent aspect of the area of WON (arrow). ( f ) T1-weighted fat-saturated post-contrast MRI: rim enhancement with central devascularization in walled-off necrosis (arrow).

As previously noted, infections are more common in necrotic collections; however, all types of collections can become infected and are typically identified through clinical symptoms of acute infection. The presence of gas within the collection, in the absence of a fistula, is an important imaging indicator of an infected collection, characterized by numerous small gas accumulations distributed throughout the collection on CT. Although prophylactic antibiotic use is ineffective in preventing infection in NP, broad-spectrum intravenous antibiotics should be administered if an infection is suspected, as these can penetrate pancreatic necrosis. Even in the absence of symptoms, infected collections may require intervention. ¹⁸ The choice between percutaneous, endoscopic, and surgical intervention depends on the specialists' expertise, the location or anatomy of the collection, available resources, and patient preferences. ¹⁹

Fistulization can also occur, both as a primary complication and secondary to pancreatic cystic lesions and necrosis. Complications of pancreatic fistulae (PF), such as hemorrhage and sepsis, can be life-threatening and require prompt diagnosis and intervention. CT is typically the initial diagnostic test used. Magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) are more sensitive than CT scans and can assess the pancreatic duct for leaks or disconnections, which can influence treatment decisions. In cases of pancreatic duct disruption, ERCP also offers therapeutic benefits by allowing for the placement of a stent across the main pancreatic duct. In protracted cases involving bowel fistulization, it is essential to eliminate sources of ongoing infection by draining any residual pancreatic collections or necrosis, which may initially expand the size of the fistula. Common strategies for managing PF include reducing fistula output with somatostatin analogs in pancreatic-pleural fistula and lowering intraductal pressure through ERCP, endoscopic ultrasound (EUS), or surgical interventions. More than half of internal PFs close with nonsurgical treatments. Surgical intervention may be required for medically refractory PF, colonic fistulas, or PF associated with a disconnected pancreatic duct, potentially involving distal pancreatectomy or bowel resection. ^{20 21} It is important, however, to perform these surgical procedures after the acute inflammatory phase of pancreatitis has resolved.

Management of Peripancreatic Collections

Management of peripancreatic collections in AP depends on the type of collection, timing, and clinical presentation. ²² Conservative management is indicated in the early phases of AP, which includes fluid resuscitation, nutritional support, and pain management. Based on the severity of the symptoms, feeding tubes may be necessary to initiate enteral feeding, as recent evidence has suggested against prolonged parenteral nutrition. ²³ For pervasive, symptomatic complications of AP, especially those persisting for more than 3 weeks, a step-up approach has been suggested by the literature. Endoscopic transgastric drainage or image-guided, minimally invasive percutaneous interventions are considered first for the management of lesions, followed by more invasive surgical treatments. ^{24 25}

Aspiration

Pancreatic aspiration is a procedure used to obtain a sample of pancreatic fluid or tissue for diagnostic purposes. This procedure can be done through various methods, such as EUS or image-guided percutaneous aspiration. Aspiration of pancreatic secretions can be clinically indicated if there is concern of infected necrotizing pancreatitis and imaging findings are not sufficient to establish the diagnosis, or if there are findings concerning malignancy on MRI or CT. Specimens are acquired under CT guidance, and a 20- to 22-gauge needle is used to obtain access to the desired collection and to acquire the specimen. ²⁶

Aspiration can also be performed per-orally and through the hollow GI organs using EUS. EUS-guided aspiration is particularly preferred in aspirating lesions less than 3 cm. For this purpose, a 22-gauge needle is used. ²⁷

Studies have suggested that percutaneous and EUS aspiration may have similar rates of diagnostic accuracy and technical success; however, EUS is preferred in cases where there is a suspicion of malignancy. ²⁸ In cases of AP and suspected malignancy, diagnostic procedures are deferred until after the acute inflammatory phase has resolved.

Drain Placement

Infected pancreatic necrosis is one of the main indications for placement of drains in AP either endoscopically or percutaneously, though earlier placement of drains may be indicated in cases of large fluid collections causing local mass effects such as biliary or bowel obstruction, compartment syndrome, or clinical deterioration. Percutaneous over endoscopic drainage is often preferred in critically ill patients, as monitoring capabilities in an interventional radiology suite are comparable to the level of an intensive care unit. Percutaneous drain placement could also be used as a bridging therapy for necrosectomy.

Endoscopic transmural drainage can be performed either by endoscopic guidance or by using EUS. Most centers perform endoscopic procedures in relatively stable patients as most endoscopy suites are not equipped to manage critically ill patients. Metallic or plastic stents (7–10 Fr) are used for drainage of collections. ²⁹ The newer generation of stents such as lumen-apposing metal stents (LAMS) (AXIOS stent; Boston Scientific, Marlborough, MA) is currently preferred for drainage. Specifically, these stents help with direct endoscopic necrosectomy. LAMS are fully covered, dumbbell-shaped stents that significantly decrease the risk of stent migration and have a larger diameter which facilitates drainage and allows easier access to the necrotic cavity. ³⁰

After the collection is detected using EUS, the surrounding structures are assessed to determine any risk for vessel perforation. A 19- to 20-gauge needle is used to puncture through the gastric or duodenal wall and is advanced into the collection, A 0.035-inch guidewire is introduced through the needle and is coiled inside the cavity. Endoscopic cannulas and catheter dilators are used to dilate the tract, and the stents are inserted. ³¹

Percutaneous catheter drainage is best performed retroperitoneally through the flank, as the drain will avoid the intestines and major vessels. The transperitoneal approach is considered when the target collection is located at the head or proximal body of the pancreas. The preferred drain size is based on the contents of the collection. Liquefied collections are usually treated with a 10- to 32-Fr drain, while those with more solid components require large bore drains. If necessary, two drains can be inserted into the same collection (known as the kissing catheter technique) with one drain being used for flushing and another for aspiration of the fluid. Double-lumen catheters can also be used in such circumstances. ^{32 33} The Seldinger or the trocar technique can be used to gain access to the collection using image-guided percutaneous interventions. In the Seldinger technique, an 18-gauge needle is used to gain access to the collection under ultrasound or CT guidance, and then a 0.035-inch stiff or super-stiff guidewire is inserted, and the tract is serially dilated to enable placement of the drain. This technique is most useful for deep collections or locations with limited endoscopic access. In the Trocar technique, a coaxial combination of a stylet, a stiff cannula, and a drain is advanced into the collection. This technique is best suited for superficial collections. Fig. 3 presents a patient with pancreatic collection undergoing percutaneous drain placement, with subsequent improvement of the collection.

Fig. 3.

( a ) Axial contrast-enhanced CT of the abdomen showing extensive areas of low attenuation within the pancreatic bed (arrows), consistent with walled-off pancreatic necrosis. The necrotic collection contains non-enhancing, heterogeneous material with some gas pockets, indicating the presence of necrotic debris and possible secondary infection. The adjacent tissues exhibit significant inflammatory changes and fluid collections, typical of acute necrotizing pancreatitis. The presence of gas within the collection is indicative of communication with the gastrointestinal tract, likely due to previous interventions or a fistulous connection. ( b ) Post-drain placement image of the same patient. The surrounding inflammatory changes have decreased, and the amount of intraluminal gas is reduced, but some residual solid components persist (arrows).

Necrosectomy

In vivo studies have suggested that multiple pathophysiologic processes are involved in pancreatic necrosis development. The most important processes include the activation of local proinflammatory cellular signaling pathways resulting from enzymatic activation and autodigestion of the pancreas. ³⁴ This leads to irreversible damage to the pancreatic parenchyma and systemic dysregulation of the microcirculation within the pancreatic tissue, resulting in hypoxia and the subsequent generation of reactive oxygen species. These reactive oxygen species further propagate cellular damage and proinflammatory responses, leading to a vicious cycle of microcirculatory impairment. ³⁵ Pancreatic necrosis indicates a permanent state where a portion of the pancreas loses its blood supply. Although this condition is irreversible, many instances of “necrosis” ultimately result in a pancreas that appears normal on CT or ERCP after recovery. ³⁶

In approximately 1 to 9% of AP cases, a WON develops. WON can involve both the pancreas and the surrounding peripancreatic tissues. It may extend into the retroperitoneal space, often involving nearby structures such as the stomach, duodenum, and colon. The collection is enclosed by a thick, fibrous, and inflammatory wall that forms in response to the necrotic process. The wall is typically made up of granulation tissue which maturates overtime, and lacks an epithelial lining. WON can be located in single or multiple locations and vary in size. ³⁷

Percutaneous Image-Guided Necrosectomy

Mechanical Necrosectomy

Mechanical necrosectomy encompasses all minimally invasive techniques using drainage catheters, baskets, retrieval nets, or adapting thrombectomy devices for retrieving necrotic tissue. Conventionally, endoscopic necrosectomy was performed using the devices. Recently, more specialized endoscopic debridement systems, such as the EndoRotor (Interscope Inc, Northbridge, MA), have been proposed. This device generates negative pressure at its tip, drawing the necrotic tissue onto its tip, which contains a guarded rotating blade. ³⁸

For percutaneous interventions, interventional radiologists have traditionally used snares, baskets, nephroscopic instruments, and drainage catheters. ³⁹ Recently published literature has also provided preliminary evidence regarding the adaption of thrombectomy devices, such as the over-the-wire Arrow-Trerotola percutaneous thrombolytic device. This device has an expandable 9-mm (∼0.35 inch) fragmentation basket, complemented by an activated spinning basket that can easily macerate the target tissue. ⁴⁰

As mentioned previously, the current body of literature strongly suggests delayed interventional management of pancreatic collections. Currently, the step-up approach is viewed as the preferred method of managing such lesions. ¹⁴ The first step is percutaneous drainage of the collection, which may even obviate the need for more invasive procedures in some cases. Patients in need of further debridement can undergo endoscopic-guided cystogastrostomy, video-assisted retroperitoneal debridement (VARD) or sinus tract endoscopy, or a combination of procedures. Not all patients are suitable candidates for an endoscopic procedure, especially those with larger collections, collections with vascular pseudoaneurysms, or collections not close to the stomach wall or the duodenum (> 1 cm). ⁴¹

Patient selection for combined mechanical and chemical necrosectomy is best performed via a multidisciplinary team consisting of gastroenterologists, interventional radiologists, and gastrointestinal surgeons. Percutaneous necrosectomy is performed within 1 week of percutaneous drain placement at the earliest. The first step involves assessing the necrosis cavity by injecting diluted contrast medium to check for any secondary complications such as fistula formation. The amount of fluid used to opacify the cavity can help gauge the amount of H ₂ O ₂ needed for optimal necrosectomy. It is suggested to inject 3 to 5 mL less H ₂ O ₂ to minimize the risk of an extracavity leak of H ₂ O ₂ .

Based on our experience, combining mechanical and chemical necrosectomy enables more conservative management of patients, often eliminates the need for additional open surgery, and also decreases the number of interventions. After chemical necrosectomy, a short, stiff guidewire with an atraumatic flexible tip, such as the 75-cm 0.035-inch Amplatz wire, can be advanced through the existing drain to secure access and enable the exchange of the drain with a peel-away sheath, followed by the insertion of an access catheter (such as the Kumpe catheter). An optimal access catheter provides the control, pushability, and torque response necessary for navigating the necrotic cavity.

The indwelling system, consisting of the stiff wire and the guide catheter, is used to access necrotic debris. Once found, the access catheter is exchanged for mechanical thrombectomy. A Universa Malecot anchor drainage catheter (14–16 Fr) can be introduced over the wire, and by applying rotational force to the catheter can facilitate the breakdown of the debris via the blades located at the tip of the catheter. If the necrotic debris persists, Arrow-Trerotola percutaneous thrombolytic device can be used to perform for mechanical necrosectomy. After the removal of all debris, a straight drainage catheter with side holes is placed, the cavity is flushed twice with normal saline, and it is connected to an accordion drain that allows for continuous suction from the drain. Although the Arrow-Trerotola percutaneous thrombolytic device has been recalled by the FDA, alternative approaches are still available such as utilizing other nitinol baskets or forming loops by suturing two Benson wires. Figs. 4 and 5 present an image series of patients undergoing mechanical necrosectomy.

Fig. 4.

( a ) Axial CT scan of the abdomen, illustrating a large heterogeneous collection in the pancreatic region consistent with pancreatic necrosis (arrows). The collection contains both fluid and nonenhancing debris, characteristic of necrotic material. ( b ) Fluoroscopic sinogram, performed after the insertion of a percutaneous drain. The sinogram reveals the communication between the drain and the necrotic collection, confirming proper drain placement within the necrotic cavity (arrowheads). The irregular filling defects seen on the sinogram are consistent with the presence of solid necrotic debris within the collection (arrows). ( c ) CT scan post-drain placement demonstrating good placement of the drain in the lateral aspect of the collection.

Fig. 5.

( a ) Fluoroscopic image of the Arrow-Trerotola PTD used for mechanical necrosectomy in a patient with necrotic pancreatic collection, performed in a step-up approach (circle). ( b ) Post-necrosectomy CT imaging of the pancreas showing optimal necrosectomy, reduced interstitial edema, and minimal peripancreatic fluid collection (circle). ( c ) The retrieved necrotic material post-necrosectomy.

Based on immediate and early postoperative imaging, continued sessions of mixed necrosectomy can be performed in 7 to 10 days. During this period, and between treatment sessions, the output of the drain is monitored, and the indwelling drain is periodically downsized to promote the formation of granulation tissue and closure of the tract. ⁴²

Chemical Necrosectomy

Chemical necrosectomy is the process of removing necrotic tissue using chemical agents, involving their local injection and subsequent retrieval. The majority of studies using chemical necrosectomy have emerged from gastroenterology literature, with the delivery of the caustic agents by the transgastric route. However, there is a growing interest in combined mechanical and chemical necrosectomy using percutaneous access. ⁴³

Several compounds have been used for necrosectomy purposes in general, such as hydrogen peroxide (H ₂ O ₂ ), streptokinase, papain-urea, sodium hypochlorite (NaOCl), and collagenase. ³⁵ However, H ₂ O ₂ is most commonly used in pancreatic pathologies. H ₂ O ₂ is a strong oxidizing agent that decomposes to water and oxygen, producing a bubbling effect that can help mechanically remove necrotic tissue. Furthermore, the released oxygen can turn into hydroxyl radicals, superoxide anions, and singlet oxygen. These can penetrate cell membranes and interact with cellular molecules, leading to damage in these components and inducing oxidative stress. Studies have shown that this breakdown in cellular components is associated with tissue dehiscence and mucolytic properties. ³⁶

Usually, a 3% H ₂ O ₂ solution is diluted with normal saline and contrast medium (with a ratio of 1:3–5:3–5) when injected percutaneously, and a 3% H ₂ O ₂ solution diluted 1:1 to 1:10 with normal saline is used in the endoscopic injection. A meta-analysis performed on 454 patients showed that hydrogen peroxide-assisted endoscopic necrosectomy was associated with a technical success rate of 97.3%, with 17.9% experiencing side effects. Bleeding was the most reported side effect with a frequency of 7.1%, and no H ₂ O ₂ -specific side effect was seen (such as embolic events). ³⁷

Streptokinase is another chemical agent commonly used in pancreatic necrosectomy. Streptokinase acts on the superficial layers of the necrosum and causes lysis of the cellular structures and its eventual dissolution. This leads to better drainage of solid contents of the necrotic cavities. ³⁸ Currently, there is limited evidence regarding the comparative efficacy of streptokinase and H ₂ O ₂ ; however, the existing studies show similar rates of technical and clinical success, with no significant differences in complications such as hemorrhage, sepsis, or extended posttreatment hospital stay. ³⁹

Clinical Outcomes of Percutaneous Necrosectomy

Initial evidence emerging from small-scale studies has had mixed results, with the rate of success depending on procedural details and instruments used. In one such study conducted over a time period of 12 years, the results of necrosectomy using continuous saline flush, soft-tip catheters, snares, and Dormia baskets were reported. A total of 18 patients were included, with 8 achieving complete recovery. Ten patients eventually required surgical intervention; of these, six had a complete recovery, while four died due to complications of surgery (three patients had septic shock, and a single patient died due to massive pulmonary embolism). ⁴⁴

A similar retrospective study over the span of 16 years included 63 patients undergoing continuous aggressive lavage using multiple percutaneously placed catheters. Of the 62 patients who completed at least one lavage procedure, 50 were exclusively treated with lavage, and 12 required a step-up to open surgery either due to technical failure of lavage or exacerbation of clinical signs and symptoms. Of all the patients, 47 had stable vital signs following drainage, with none experiencing adverse clinical outcomes, while 15 were unstable and intubated, of which seven died. ⁴⁵

In one of the most recent studies, technical and clinical outcomes of necrosectomy were compared between 13 patients undergoing combined chemical and mechanical necrosectomy and 11 patients undergoing mechanical necrosectomy alone. Technical success was achieved in all patients in both groups. However, the group undergoing combined mechanical and chemical necrosectomy achieved higher clinical success rate with lesser number of interventions (100 vs. 38.4% in the mechanical necrosectomy alone; resolution of the cavity within 7 to 10 days). ⁴⁰

Non-IR Interventions

Open Surgery

The open surgical technique was considered the gold standard treatment option before the introduction of minimally invasive surgical procedures. This technique is used in documented infection of the pancreatic necrosum, or when sterile necrosis is seen concomitantly with progressive clinical deterioration, massive intra-abdominal hemorrhage, or hollow viscus perforation. ⁴⁶

First, an upper midline incision above the umbilicus is made to minimize the risk of incisional hernia. This approach preserves the rectus abdominis muscles and provides excellent access to the pancreas and the surrounding vascular and nonvascular structures. This incision can also be used when bowel resection is anticipated. A parallel approach is to perform a transverse subcostal laparotomy, which also provides optimal access to the pancreas and necrotic tissue but is less versatile and has more morbidity. Pancreatic debridement can be performed either by entering the lesser sac through the gastrocolic ligament or through the bare area of the transverse colon mesentery. The surgeon then proceeds to remove necrotic debris manually with forceps, a suction irrigator, a spoon, or a combination of all through. It is paramount to avoid exerting significant force when removing necrotic debris, as this can cause bleeding from major vessels that are still adherent to the necrosis. Dissection of the necrotic tissue is performed based on the necrotic extension seen in postoperative CT imaging, which may show the expansion of the necrosum to the retroperitoneum, perirenal and anterior-renal spaces, or the right paracolic gutter. After debridement of all necrosum that can be readily separated from the surrounding tissue, lavage with normal saline is performed, and drains are placed. ^{14 47 48}

The landmark study by the Dutch Pancreatitis Group published in 2010 demonstrated a lower complication rate in patients assigned to the minimally invasive approach over open necrosectomy, which shifted practice patterns away from open techniques. If necessary, open laparotomy is undertaken as late as possible, ideally after 4 weeks from the onset of fluid collections associated with acute necrotizing pancreatitis, when necrogenesis has ceased, viable and nonviable tissues are well-demarcated, and infected necrotic tissues are confined. If earlier laparotomy is needed to address other complications (bowel perforation/necrosis), care must be taken not to attempt aggressive necrosectomy but rather to perform wide drainage until mature necrotic collections have formed.

Laparoscopic Necrosectomy

The patient is positioned in the French position. A pneumoperitoneum is created by inserting a 12-mm optical trocar infraumbilically, followed by diagnostic laparoscopy. Two lateral pararectal trocars are inserted under vision, and peripancreatic adhesions are released by blunt dissection. The approach to the pancreatic necrotic tissue is determined based on the status and location of the necrosis as shown by preoperative CECT. The retrogastric approach, either transgastrocolic or transmesocolic/infracolic, is preferred.

In the transgastrocolic approach, the gastrocolic ligament is opened to access the necrotic tissue, suitable for necrosis in the head and body of the pancreas. The transmesocolic or infracolic approach, used for necrosis in the tail of the pancreas, involves opening the mesocolon near the ligament of Treitz. The necrotic tissue is dissected and removed using blunt dissection in an endobag. The cavity is washed with normal saline, and two 30-Fr tube drains are placed for postoperative lavage. ⁴⁸ For patients with WON or predominantly liquid necrosis, transgastric and intracavitary approaches are preferred. If the stomach can be adequately distended, the intracavitary approach is used. The transgastric approach involves creating an 8-cm distal gastrotomy in the anterior stomach wall with a 5-mm ultrasonic dissector. The lesser sac is entered through the posterior gastric wall after confirmation by aspiration, and a gastrotomy is created with a linear stapler. Pus is aspirated, and the cavity is irrigated with warm normal saline. Pancreatic necrosectomy is performed with a suction device and nontraumatic grasping forceps, and the debrided tissue is removed in an endobag. The lesser sac and peritoneal cavity are copiously irrigated with warm normal saline. The anterior gastrotomy is closed, and a 16-Fr suction drain is placed in the left subphrenic space to drain residual lavage fluid. ⁴⁹

In the intracavitary approach, after inserting the trocars, the anterior stomach wall is pulled anteriorly and fixed to the abdominal wall with transfascial sutures. Two 5-mm trocars are inserted into the stomach, which is insufflated with CO ₂ . A 5-mm telescope is introduced, and the posterior cystogastrostomy is completed with an ultrasonic dissector after confirmation by aspiration. Necrotic tissue is emptied into the stomach, and a thorough wash with warm normal saline is performed.

Videoscopic-Assisted Retroperitoneal Debridement

VARD is a minimally invasive surgical technique used in the step-up approach, and is performed under general anesthesia after percutaneous pancreatic drainage has been performed. Prior to proceeding with VARD, percutaneous drains are generally upsized to 16 to 18 Fr to facilitate access to the infected necrosis. The patient is positioned in the supine or lateral decubitus position, and the incision site is marked for a length of 2 cm along the inferior costal margin at the location of the percutaneous drain. The drain is followed through the retroperitoneum with retractors, cautery, and blunt dissection until entry into the infected necrosis. At this point, a trocar can be inserted, and the drain removed. A zero-degree laparoscope or nephroscope with continuous irrigation is introduced into the cavity and forceps are used to remove the necrotic tissue. If a nephroscope is used, forceps can be inserted through a working channel. Alternatively, additional instruments can be inserted directly through the retroperitoneal incision or another trocar, depending on the size of the cavity and its distance from the skin surface. Irrigation and suction can also be used to remove debris and infected material. In some cases, multiple ports may be required to improve access and facilitate thorough debridement. ⁵⁰ It is important to mention that the ultimate goal of this procedure is to only remove loosely adherent necrotic pieces, as more aggressive necrosectomy has been shown to be associated with increased rates of complications, and conversion to open laparotomy. After sufficient necrosectomy is performed, the existing drain is removed, and a larger-bore drain is inserted into the cavity. The drain is continuously irrigated for the first 24 to 48 hours and subsequently flushed three times daily depending on the presence of necrotic debris on subsequent CT imaging. ⁵¹ Additional procedures may be required based on repeat imaging.

Endoscopic Pancreatic Necrosectomy

Similar to other therapeutic measures, EUS necrosectomy is usually performed 4 to 6 weeks after acute symptoms of pancreatitis. ²⁴ An endoscope with a suitable working channel is passed into the stomach or duodenum based on the anatomy of the collection, and the necrotic cavity is punctured and accessed through the hollow GI organs using a needle knife. A stiff guidewire is then inserted through the stomach or duodenum and coiled inside the cavity, and the needle knife is removed. While the needle knife is being removed, it is imperative to have constant suction of the gush of fluids from the necrotic cavity to decrease the likelihood of fluid aspiration. After this, a balloon is used to dilate the puncture tract. The balloon is sequentially inflated and deflated to ensure that no significant hemorrhage is caused by the dilation. Afterward, CO ₂ gas is used to insufflate the cavity, and the balloon is removed. Rinsing of the cavity is performed using an endowasher and necrotic debris is removed from the cavity. Mechanical necrosectomy can also be attempted using Dormia-baskets or polypectomy snares. Each session of EUS necrosectomy should be kept to less than 90 minutes to minimize complications; thus, most patients will need to undergo multiple sessions of treatment within 2 to 3 days of intervals. To retain access between the necrosectomy sessions, a fully covered metal stent is inserted into the created lumen and is kept until the last session. ^{52 53}

Trends and Future Developments

The field of minimally invasive percutaneous necrosectomy for managing complicated pancreatitis is poised for significant advancements. Current trends highlight a continued emphasis on refining and optimizing minimally invasive techniques to enhance patient outcomes and reduce procedural complications, and procedural duration. The ongoing development of advanced endoscopic and percutaneous tools, such as specialized retrieval devices and an improved combination of chemical agents with established mechanical necrosectomy devices, is expected to further increase the clinical success rate of percutaneous necrosectomy procedures. Moreover, the adoption of tailored chemical necrosectomy approaches, including the use of novel agents and optimized dilution protocols, aims to enhance the selective debridement of necrotic tissue while minimizing systemic side effects.

Future research is likely to focus on comparative studies to establish the most effective combinations of mechanical and chemical debridement, optimizing protocols based on specific patient and necrotic collection characteristics. Furthermore, studies focusing on patient selection for minimally invasive necrosectomy could elucidate optimal candidates for endoscopic and percutaneous necrosectomy. Also, newer devices could be studied for percutaneous necrosectomy, such as the EndoRotor-powered endoscopic debridement device, over-the-scope-grasper, and the waterjet necrosectomy device. ^{54 55 56} In recent years, several multicenter studies have been published, demonstrating a favorable safety profile for endoscopic application of these devices, thereby expanding less invasive treatment options to a broader range of patients. ⁵⁷

Additionally, advances in imaging technologies and real-time monitoring during procedures may offer better precision and early detection of complications. The shift toward personalized treatment plans, guided by multidisciplinary teams, will become more prevalent, emphasizing individualized approaches to necrosectomy based on patient-specific factors and evolving clinical guidelines.

Conclusion

Peripancreatic fluid collections are a common complication of AP that can be fluid-filled or necrotic. They can be classified as early or late, depending on when they develop. Necrosectomy remains a critical component in the management of pancreatic necrosis, particularly in the context of late-stage pancreatic lesions. The current step-up treatment paradigm favors endoscopic transgastric interventions, followed by percutaneous interventions. The choice of a surgical approach—whether transgastrocolic, transmesocolic, or intracavitary—depends on the specific location and extent of the necrosis, as well as the patient's overall condition. Advances in imaging and minimally invasive techniques, and a combination of mechanical and chemical necrosectomy, have improved the precision and outcomes of necrosectomy, allowing for the effective removal of necrotic tissue while minimizing surgical trauma. Proper preoperative planning, accurate imaging, and tailored surgical strategies are essential for optimizing patient outcomes. Ongoing advancements in techniques and postoperative care continue to enhance the efficacy and safety of image-guided percutaneous necrosectomy.