Pancreatic debridement

INTRODUCTION — Pancreatic debridement is indicated for patients with pancreatic necrosis and progressive clinical sepsis or severely symptomatic sterile necrosis as a complication of severe acute pancreatitis [1,2]. Pancreatic and peripancreatic necrosis occurs in approximately 20 percent of patients with acute pancreatitis, as a result of inflammation and vascular compromise [3,4].

The goal of pancreatic debridement is to excise all necrotic and devitalized pancreatic and peripancreatic tissue while preserving viable functioning pancreas, controlling pancreatic fistulas, and limiting extraneous organ damage [1,5]. For patients with biliary pancreatitis, cholecystectomy is an important secondary objective of the surgery because it will prevent recurrent disease [6].

In contemporary practice, necrotic pancreatic and peripancreatic tissue can be debrided endoscopically or surgically. The indications and techniques for surgical pancreatic debridement will be reviewed here. Endoscopic debridement is discussed separately. (See "Endoscopic interventions for walled-off pancreatic fluid collections".)

The etiology, diagnosis, and general approach to the treatment of acute pancreatitis is discussed elsewhere. (See "Etiology of acute pancreatitis" and "Clinical manifestations and diagnosis of acute pancreatitis" and "Predicting the severity of acute pancreatitis" and "Management of acute pancreatitis".)

APPROACH TO PANCREATIC DEBRIDEMENT — Patients who require pancreatic debridement should be treated in a tertiary referral center where surgical, endoscopic, and radiologic expertise is available; the initial and subsequent approaches should be selected based on indication, timing, and anatomical considerations (algorithm 1). Whenever possible, a "step-up" approach should be used rather than upfront surgical debridement.

Indications — Pancreatic necrosis can lead to secondary infection or symptomatic sterile necrosis, which is characterized by chronic low-grade fever; nausea; lethargy; inability to eat; and/or ongoing gastric outlet, intestinal, or biliary obstruction [5,7-9]. Both infected pancreatic necrosis and symptomatic sterile necrosis are accepted indications for debridement [7,9,10]. (See "Management of acute pancreatitis", section on 'Acute necrotic collection and walled-off necrosis'.)

Asymptomatic patients with sterile pancreatic necrosis are observed as pancreatic debridement carries a much higher risk of iatrogenic complications than that of spontaneous complications of the fluid collection [11].

Timing — Pancreatic necrosis is a dynamic disease process that evolves in two distinct clinical phases (figure 1), which affect the timing of debridement and choice of techniques [12].

●Early phase – The early phase of illness (first two weeks) is characterized by an acute systemic inflammatory response syndrome, organ dysfunction or failure, and variable amounts of pancreatic and peripancreatic ischemia, leading to tissue necrosis, termed acute necrotic collection (ANC). The underlying mechanism for this phase of disease is believed to be the host's inflammatory and cytokine response, resulting in organ dysfunction [13].

During the first few days of critical illness, early death from irreversible organ failure accounts for up to 60 percent of mortality in patients with severe acute pancreatitis [14,15]. This early organ failure, which is predominately renal and pulmonary, can be treated by aggressive volume resuscitation, enteral feeding, and support [5]. In patients who survive this early inflammatory storm, increased morbidity and mortality rates are due to persistent organ failure, pancreatic necrosis, and/or infection [1,5]. (See "Management of acute pancreatitis", section on 'Initial management'.)

Infrequently, exploratory laparotomy is required for other potentially treatable causes of recalcitrant multiorgan system failure such as infarcted bowel, gangrenous gallbladder, perforated viscus, or even abdominal compartment syndrome. However, if treatable causes of organ failure are not identified and the etiology is confirmed to be severe acute pancreatitis with necrosis, early pancreatic debridement is rarely helpful. Surgical debridement earlier than four weeks is often complicated by intra-abdominal hypervascularity, altered anatomic relationships, and an inability to discriminate dead from surrounding live tissue, making debridement imprecise, bloody, and ineffective. When infected necrosis necessitates early debridement, the debridement often is associated with incomplete removal of necrotic tissue and a high rate of injury to normal surrounding tissues [16-18]. These patients have a higher morbidity and mortality rate and frequently require multiple surgical procedures for persistent pancreatic necrosis or repair of iatrogenic damage to the surrounding organs [19].

As such, in the first two to four weeks, percutaneous drainage may be considered if clinically necessary (eg, in septic patients with infected necrosis). Open debridement should be avoided as much as possible and only undertaken if the patient's necrosis is not accessible or refractory to percutaneous drainage [12]. Endoscopic debridement is generally not feasible, due to the lack of a mature wall [11], although there are some data that early endoscopic debridement may be possible but with more interventions and drainage for a longer duration [20]. (See 'Percutaneous CT-guided catheter drainage' below.)

●Late phase – The optimal time for pancreatic debridement is after four weeks from the onset of pancreatitis. Delayed debridement allows for clinical stabilization of the patient, resolution of early organ failure, and a decrease in the intense inflammatory reaction in the retroperitoneum [17,18]. After four weeks, vascular inflammation has decreased, organization of the process has occurred, and delineation of devitalized tissue is complete [21]. At this point, the retroperitoneal inflammatory response decreases and the necrotic areas are demarcated from the surrounding viable tissue, which usually permits definitive operative debridement. The organized, demarcated collection is termed walled-off pancreatic necrosis (WOPN) [22,23]. WOPN is amenable to both endoscopic and surgical debridement; the former also requires that the collection has a mature wall and is directly opposed to the stomach or duodenum. (See 'Endoscopic debridement' below and 'Surgical debridement' below.)

Anatomical considerations — Location of the pancreatic necrosis, as ascertained by preoperative cross-sectional imaging, is a key factor in guiding approaches to debridement [12,24]. (See 'Computed tomography' below and 'Surgical debridement' below.)

●Retrogastric collections that extend into the left paracolic gutter can be drained from a left retroperitoneal approach, starting with percutaneous drainage and, once access is established, followed by minimally invasive retroperitoneal pancreatectomy (MIRP) or video-assisted retroperitoneal debridement (VARD) if necessary. (See 'Video-assisted retroperitoneal debridement' below and 'Minimally invasive retroperitoneal pancreatectomy' below.)

Alternatively, such collections can be drained endoscopically and, if needed, combined with additional percutaneous drains to address the dependent component in the left paracolic gutter.

●Central collections contained within the lesser sac that interface with the posterior gastric wall can be debrided in a transgastric fashion, either endoscopically, laparoscopically, or open. Endoscopic debridement is generally preferred as it has fewer complications but often requires multiple procedures. Surgical debridement is more definitive but has a higher complication rate. (See 'Laparoscopic transgastric debridement' below and 'Open transgastric debridement with cystgastrostomy' below.)

●Collections in the root of the mesentery or to the right of the mesenteric vessels are difficult to access percutaneously, endoscopically, or retroperitoneally and thus may require either laparoscopic transperitoneal or traditional open approaches. (See 'Laparoscopically transperitoneal debridement' below and 'Open debridement with external drainage' below.)

●Disconnected pancreatic duct syndrome (DPDS) is caused by necrosis and disruption of the main pancreatic duct, leaving the pancreatic segment to the left of the disruption disconnected from the gastrointestinal tract. The standard treatment of DPDS is a distal pancreatectomy (resection of the disconnected segment) at the time of an open debridement or as a separate, delayed operation. Alternatively, DPDS can be treated with endoscopic transmural stenting or surgical transgastric drainage (utilizing the cystgastrostomy as an internal drain).

Step-up approaches — In suitable candidates, a "step-up" approach of percutaneous drainage and/or endoscopic drainage/debridement provides minimally invasive alternatives to surgery that can be equally effective [25] and may be associated with reduced mortality [26].

●The PANTER study (PAncreatitis, Necrosectomy versus sTEp up appRoach), a randomized trial of percutaneous catheter drainage in 88 patients, found that 35 percent of patients were treated successfully with percutaneous catheter drainage alone, while the remainder required percutaneous drainage followed by VARD [27,28]. Compared with open pancreatic debridement, preoperative drainage followed by VARD significantly decreased the rate of new-onset multiple organ failure (12 versus 40 percent), incisional hernias (7 versus 24 percent), and new-onset diabetes (16 versus 38 percent) but did not significantly affect mortality.

●Another multicenter Dutch trial compared endoscopic catheter drainage followed by endoscopic necrosectomy (if necessary) with percutaneous catheter drainage followed by VARD (if necessary) [29]. Ninety-eight patients with infected pancreatic necrosis were randomly assigned after four weeks since the onset of symptoms to ensure that they had at least partial encapsulation of the necrotic collection. Forty-three and 51 percent of patients in the endoscopic and VARD groups, respectively, only required catheter drainage. Compared with surgery, endoscopic treatment resulted in similar mortality plus major morbidity rate at six months (43 versus 45 percent) but lower incidence of cardiovascular organ failure (6 versus 19 percent), fewer pancreatic fistulas (5 versus 32 percent), and a shorter hospital stay (by 16 days). Approximately one-third of patients treated endoscopically required additional percutaneous catheter drainage or VARD.

●A single-center American trial compared minimally invasive surgery (laparoscopic or VARD) to the endoscopic step-up approach in 66 patients with WOPN [30]. At six months, fewer patients in the endoscopic group had major complications or death (12 versus 41 percent) or fistulas (0 versus 28 percent) compared with those in the surgery group.

●A network meta-analysis of seven studies including 400 patients with infected pancreatic necrosis found that the step-up approach with endoscopic debridement had the highest probability of being the safest approach (surface under the cumulative ranking curve [SUCRA] 87.1 percent), followed by the step-up approach with delayed minimally invasive surgical debridement (SUCRA 59.5 percent); delayed surgical debridement, early surgical debridement, and peritoneal lavage had the lowest probability of being safe (SUCRA values 27.6, 31.4, and 44.4 percent, respectively) [21].

PREOPERATIVE PREPARATION

Computed tomography — All patients with pancreatic necrosis undergoing debridement should have contrast-enhanced computed tomography (CT) scanning of the abdomen and pelvis. Accurate quantification of the extent of pancreatic parenchymal and peripancreatic necrosis, documentation of diffuse or walled-off necrosis, and identification of infection are critical for the prediction of a patient's clinical course and choice of the most appropriate therapy [1,7,31-33].

●Assess necrosis – Areas of necrosis are manifested on contrast-enhanced CT by a lack of tissue contrast enhancement (fewer than 50 Hounsfield units) (image 1) [31,34]. The lack of contrast is due to capillary thrombosis and documents the lack of blood supply to the area of necrosis [35]. Use of CT findings to predict outcome is outlined in the table (table 1) and discussed in detail elsewhere (see "Predicting the severity of acute pancreatitis", section on 'CT severity index'). Some studies suggest that CT is not as good as magnetic resonance imaging (MRI) in differentiating necrotic tissue from fluid [36].

●Assess infection – The diagnosis of infected pancreatic necrosis is made by the identification of air bubbles in retroperitoneal necrosis on CT (image 2) and/or with CT-directed fine-needle aspiration of pancreatic necrosis for Gram stain and culture [22,37]. While air bubbles can indicate from either infection or fistulization from a hollow viscus, the use of CT-directed fine-needle aspiration confirms the diagnosis of infected pancreatic necrosis and supports the decision for debridement. However, because of potential adverse effects, fine-needle aspiration should be performed only when the results will affect intervention [38]. (See "Management of acute pancreatitis", section on 'Acute necrotic collection and walled-off necrosis'.)

●Estimate disease extent – Extension of the necrotic process into the mesenteric root (image 3) and down the right and left paracolic gutters is common and should be treated with wide debridement and drainage (sometimes requiring additional drains). (See 'Anatomical considerations' above.)

●Assess walled-off necrosis – Best defined by cross-sectional imaging, walled-off pancreatic necrosis is a well-recognized entity in which encapsulation of the process within the lesser sac bound by the stomach, duodenum, transverse mesocolon, and omentum creates a localized mature collection analogous to a pancreatic pseudocyst (image 4 and image 5) [33]. Walled-off pancreatic necrosis is well suited to minimally invasive debridement techniques, including endoscopic transgastric drainage, external percutaneous drainage with irrigation (image 6 and image 7), and video-assisted retroperitoneal debridement. (See 'Timing' above.)

Informed consent — The indications for debridement and the planned method of debridement should be discussed with the patient. The discussion should include the potential need for multiple interventions or reoperations to drain intra-abdominal fluid collections, remove additional necrotic tissue, or control a pancreatic fistula as well as the possible complications of each method.

Patients with biliary pancreatitis should be informed that cholecystectomy done in the setting of retroperitoneal inflammation is associated with an increased incidence of postoperative bile leak or biliary injury. Patients with involvement of the mesocolon should be informed of the potential need for colon resection and a colostomy.

Antibiotics — Patients should receive preoperative antibiotics within one hour of pancreatic debridement. The most common organisms causing infection in necrotizing pancreatitis include Escherichia coli, Pseudomonas, Klebsiella, and Enterococcus, and the initial recommended antibiotic coverage is with a carbapenem [4,39]. If percutaneous CT-guided fine-needle aspiration has been performed, the antibiotic choices should reflect the culture and sensitivity results. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults", section on 'Antimicrobial prophylaxis'.)

TECHNIQUES OF PANCREATIC DEBRIDEMENT — While open debridement was once the "gold standard" of pancreatic debridement, with technological advancement, less invasive procedures such as percutaneous drainage, endoscopic drainage/debridement, and laparoscopic debridement have replaced open debridement in the majority of cases [24].

Percutaneous CT-guided catheter drainage — Temporary percutaneous drainage can be used to decompress retroperitoneal fluid collections and allow for stabilization of patients with sepsis prior to debridement [28,29]. Percutaneous drainage can be performed before four weeks, when surgical debridement is highly morbid. After four weeks, percutaneous drainage is usually reserved for when endoscopic drainage is not available, feasible, or successful [12]. As an example, additional percutaneous drains may be required to address dependent collections in one or both paracolic gutters or the pelvis after endoscopic drainage of the central retrogastric collection. Endoscopic drainage is associated with a much lower fistula rate than percutaneous drainage.

CT guidance is used to establish percutaneous access into pancreatic fluid collections using the most direct route available, thereby avoiding intervening bowel and solid organs. For example, the left retroperitoneal access is obtained between the lower pole of the spleen, the upper pole of the left kidney, and the splenic flexure of the colon [40]. The number and size of catheters placed is dictated by the size and location of the space containing the necrosis, the viscosity of the fluid aspirated, and the amount of particulate debris. Percutaneous drainage may be performed under local anesthesia with or without sedation, or under general anesthesia, depending upon local practices and patient condition/tolerance.

After placement, the catheters undergo vigorous manual irrigation with isotonic saline every several days, combined with contrast CT scans to follow the removal of necrotic debris, assess changes in the cavity dimension, and ensure catheter lumen patency. CT-guided catheter drainage requires dedicated interventional radiologists who will perform sequential interventions as necessary [33,41,42].

Over time, small-diameter drains are upsized to larger-bore catheters for removal of necrotic debris. Such catheter tracts can be used as an entry portal for other minimally invasive debridement methods, such as video-assisted retroperitoneal debridement (VARD) or minimally invasive retroperitoneal pancreatectomy (MIRP). (See 'Video-assisted retroperitoneal debridement' below and 'Minimally invasive retroperitoneal pancreatectomy' below.)

Although percutaneous catheter drainage was used as a bridging technique for patients who are too unstable to undergo surgical debridement, approximately one-third to one-half of patients can be managed with percutaneous drainage alone [43,44].

One disadvantage to the percutaneous route is the risk of persistent pancreatico-cutaneous fistula in up to one-half of the patients [43,44]. Features that predispose to pancreatico-cutaneous fistulas include communication between the pancreatic collection and the pancreatic duct or complete obstruction of the duct [45,46]. If necessary, percutaneous drainage appears more likely to be successful in patients with normal pancreatic ducts and/or those with ductal strictures but without communication between the pancreatic duct and the pancreatic collection.

Endoscopic debridement — Endoscopic debridement is typically performed via a transgastric or transduodenal approach without the need for a transabdominal incision in patients with walled-off pancreatic necrosis [25,33,47]. (See "Endoscopic interventions for walled-off pancreatic fluid collections".)

The endoscopic technique provides a targeted approach to focal pancreatic necrosis with a reduction in the systemic inflammatory response and avoidance of the wound complications that are associated with major laparotomy incisions [33,41,48]. Contemporary studies using lumen-apposing metal stents (LAMS) report technical success rates of 98 percent, clinical success rates of 90 percent, and adverse event rates of 16 to 18 percent [49,50]. One-third of patients initially treated with endoscopic debridement ultimately need open surgical debridement [35,47].

Surgical debridement — Surgical pancreatic debridement can be performed with minimally invasive or open techniques [1,5]. Minimally invasive approaches result in less profound inflammatory response and decreased physiologic stress compared with open surgery [12,48]. Location of the pancreatic necrosis, as ascertained by preoperative cross-sectional imaging, is a key factor in guiding approaches to debridement [12,24]. (See 'Anatomical considerations' above.)

Retroperitoneal approaches — The retroperitoneal approach is suitable for draining retrogastric collections that extend to the left paracolic gutter. Two retroperitoneal techniques are most commonly used.

Video-assisted retroperitoneal debridement — The VARD procedure is best suited to patients with a central distribution of necrosis that extends down into the left paracolic gutter [12]. It is controversial whether VARD can reach necrosis to the right of the mesenteric vessels [12,24].

VARD requires preoperative percutaneous access to the retroperitoneal space, which is established via interventional radiology. Before surgery, a 12 to 14 French catheter is placed into the dominant fluid collection through a direct access site in the left upper quadrant or flank under radiologic guidance. This catheter provides an anatomic access route, which guides the subsequent operation.

The surgery is performed through an incision made directly over the drain site, which is extended directly down into the necrotic cavity. Long grasping forceps are used for debridement under direct vision. When the debridement extends into the retroperitoneum, a videoscope is inserted through the incision to allow visualization and deep mechanical debridement through the scope. Two large-bore single-lumen drains are then placed in the retroperitoneum under direct vision using the videoscope.

Continuous retroperitoneal lavage with isotonic saline or dialysis fluid is continued postoperatively at a rate of 125 mL/hour, and patients are followed for clinical progression, declining serum C-reactive protein (CRP) levels, and improvement of necrosis on contrast-enhanced CT scans. Repeated debridement is done every 7 to 10 days until the necrosis cavity is seen to be clear of debris and lined by healthy granulation tissue. At this point, irrigation is stopped and external drainage is continued until the output stops and the drains can be removed.

The advantage of VARD is minimizing the risk of peritoneal contamination. The main drawback of this approach is the limited access and visualization, which limits the amount of debris that can be retrieved and leads to multiple interventions. In addition, limited visualization precludes simultaneous cholecystectomy, intraoperative cholangiography, and feeding jejunostomy placement [47]. A meta-analysis of VARD reported a 64 percent success rate, 47 percent morbidity rate, and 14 percent mortality rate [47].

The VARD technique is a component of the "step-up" approach that has been compared favorably to upfront surgical debridement in patient outcomes in several Dutch trials [28,29]. (See 'Step-up approaches' above.)

Minimally invasive retroperitoneal pancreatectomy — This technique also requires a percutaneous catheter being placed into the dominant fluid collection before surgery through a direct access site in the left upper quadrant or flank. This catheter is then serially dilated to 30 Fr under radiologic guidance. The debridement is then carried out with a 30 Fr nephroscope with forceps and irrigation through two operating channels [51,52]. Limited by the size of the instruments, this approach may be slow and may take several trips to the operating room for larger collections.

Transgastric approaches — Surgical transgastric debridement, both open and laparoscopic, is performed through a cystgastrostomy, an operation used to treat pseudocysts [53]. All transgastric debridement procedures (endoscopic, laparoscopic, or open) are best suited to the patient with centrally located necrosis, but extension of the necrosis burden into either paracolic gutter can lead to incomplete debridement [12]. The surgical procedure is more definitive, but endoscopic debridement has fewer wound complications (eg, fistula).

Laparoscopic transgastric debridement — Two trocars are inserted into the stomach under both laparoscopic and endoscopic control. The posterior gastric wall is then examined with ultrasound to identify the walled-off fluid collection, which is confirmed by laparoscopic needle aspiration. A posterior gastrotomy is then made into the walled-off fluid collection and a cystgastrostomy created with a vessel sealer or stapler. Debridement is then performed with laparoscopic instruments.

Similar to open cystgastrostomy, laparoscopic transgastric debridement also requires a walled-off pancreatic necrosis. The internal drainage provides an effective debridement with a single operation and expedites patients' return to baseline health without the need for repeat debridement and drains [54].

The MISER trial compared minimally invasive surgery (23 laparoscopic cystgastrostomies, 9 VARDs) to endoscopic transluminal drainage with or without necrosectomy (N = 34) [30]. There were no differences in patient-important outcomes except that the fistula rate was higher in the surgical group (28 versus 0 percent). However, four of the eight patients who developed fistula underwent VARD; the other four underwent percutaneous drainage in addition to laparoscopic cystgastrostomy.

Open transgastric debridement with cystgastrostomy — Open transgastric debridement with internal drainage is favored by some surgeons as the size of the cystgastrostomy significantly increases the efficiency of necrosectomy over that of endoscopic necrosectomy. This procedure is only appropriate for patients with walled-off pancreatic necrosis. The surgery is performed via a midline incision into the peritoneal cavity [54,55].

A longitudinal gastrotomy is made along the greater curvature, and the posterior gastric wall is exposed. Intraoperative ultrasound is used to locate the walled-off pancreatic collection behind the stomach, and needle aspiration is used to confirm it. The cavity is then opened with cautery, and an endovascular stapling device is used to create a generous (8 cm) cystgastrostomy. Debridement is then performed. A nasogastric tube is placed in the cavity. A gastrostomy drainage tube (Foley catheter) is placed, and the gastrotomy is closed. The nasogastric tube is then flushed with isotonic saline every four hours for two to three days.

Laparoscopically transperitoneal debridement — The laparoscopic transperitoneal approach to pancreatic debridement uses conventional laparoscopic intraperitoneal access, utilizing one port for the video camera and two to three additional working ports [56,57]. For necrosis involving the head or body of the pancreas, access is obtained by dividing the gastrocolic ligament. For necrosis involving the tail, debridement is performed transmesocolically to the left of the middle colic artery near the ligament of Treitz.

The main drawback of this approach is the potential for peritoneal contamination. In addition, reintervention is usually not possible, because of scar tissue. For these reasons, laparoscopic transperitoneal debridement is most appropriate as a single-stage procedure for patients with walled-off pancreatic necrosis [22,58]. Retrospective series reported a morbidity of 20 percent and mortality of 4 to 18 percent with this technique [24].

This technique has fallen out of favor except for patients with a centrally located walled-off necrosis in the root of the mesentery that is not amenable to either transgastric or percutaneous drainage [59].

Open debridement — In contemporary practice, open debridement is infrequently performed when a collection is inaccessible to both percutaneous and endoscopic drainage or when the step-up approach has failed [60,61].

Open debridement with external drainage — The following steps are performed with open debridement with external drainage:

●Incision – The abdomen is opened through either an upper midline or bilateral subcostal incision. If a colostomy is anticipated, the site should be marked preoperatively.

●Entry into the retroperitoneum – The retroperitoneum is entered through the lesser sac by mobilizing the omentum off the transverse colon. Alternatively, entrance to the lesser sac can be accomplished through an avascular plane in the transverse mesocolon to the right or left of the middle colic vessels [10]. Utilizing preoperative CT imaging as a guide, specific areas of pancreatic and peripancreatic necrosis and associated fluid collections are identified.

●Debridement – Once the main site of necrosis is entered, fluid is evacuated and debridement is begun by pulling the loosely organized debris away from the firm, inflamed, viable tissue using blunt dissection, finger pinching, ring forceps, and infrequent sharp dissection. Necrotic debris should be cultured for fungus as well as aerobic and anaerobic bacteria.

Viable tissue should be preserved and can be identified by its firm, indurated appearance and consistency as well as bleeding with manipulation. Major vascular structures are characteristically well preserved, allowing careful skeletonization during the debridement.

Once the main cavity is debrided, any extension of the process is identified by gentle digital palpation from within the main cavity, exploring communicating spaces and extensions of the necrosis throughout the retroperitoneum. Debridement often extends into the fat of the mesocolon or small bowel mesentery. In both of these sites, meticulous care should be taken to avoid vascular injury, particularly to the colic, superior, or inferior mesenteric vessels.

Mobilization of the colon (eg, splenic flexure mobilization) is not advised in this setting, as the risk of colonic devascularization is high. Occasionally, the necrotic process involves the mesocolon to such an extent that adequate debridement skeletonizes the colonic blood supply, leaving the colon vulnerable to ischemic injury. In this situation, partial colectomy with end ileostomy and Hartmann's procedure is the safest and most expedient way to remove jeopardized colon, divert the fecal stream, and ensure prompt recovery and the ability to establish early enteral feeding. Patients potentially at risk for this outcome should be informed of this possibility preoperatively and be visited by an enterostomal therapist for marking. (See "Ileostomy or colostomy care and complications".)

●Cholecystectomy – For patients with biliary pancreatitis, a cholecystectomy should be performed if technically possible, dissecting the gallbladder retrograde from the fundus to the infundibulum. (See "Open cholecystectomy".)

●Feeding tube – Enteral access should be established through a gastrojejunal feeding tube (18 or 22 French T-tube or a low-profile feeding tube) placed via a Stamm-type gastrostomy, directing the distal jejunal feeding port past the pylorus and ligament of Treitz into the first portion of the jejunum (figure 2).

●Drain placement – Two to four large (19 French) closed suction drains are placed at the time of operation, with the number and positioning dictated by the extent of debridement and concern for the development of a postoperative pancreatic fistula.

Open debridement with open packing — Open packing with planned reoperation every 48 to 72 hours until the necrosis is adequately removed is only appropriate when early surgical intervention is required or when the necrosis is too poorly demarcated to permit complete debridement [62] (see 'Timing' above). The open packing method is effective in controlling intra-abdominal sepsis but mandates multiple laparotomies, which increases overall mortality, the length of hospital stay, and the incidence of postoperative enterocutaneous fistulas and incisional hernias [63]. Because of these concerns, open packing should be utilized sparingly and is primarily indicated for patients with large collections extending across the retroperitoneum and into the retrocolic spaces or when bleeding is difficult to control [35].

A nonadherent gauze should be placed over the exposed stomach and colon to prevent inadvertent debridement of the intestinal tract [35]. Packing is kept moist. Drains are placed at the time of final laparotomy and secondary closure.

POSTOPERATIVE COMPLICATIONS — The reported mortality rate in contemporary series of patients undergoing open debridement of pancreatic necrosis has decreased from 25 to 60 percent historically to 4 to 18 percent owing to better understanding of the disease process and improved critical care [18,61,64]. The mortality rate is related to the extent of necrosis, underlying organ failure, and infection of the necrotic tissue [1,7,31-33].

However, the morbidity rates still range from 48 to 88 percent. Complications after pancreatic debridement include intra-abdominal fluid collections, bleeding, pancreatic fistulas, incisional hernias, and pancreatic insufficiency.

●Intra-abdominal fluid collections – The most common postoperative complication requiring intervention after debridement is residual fluid collection [1]. These collections are frequently infected and can result from a pancreatic leak inadequately controlled by the drains placed at surgery or from a hollow viscus injury. Intra-abdominal fluid collections can be identified on CT scan and are managed with percutaneous drainage [1,5,7]. Reoperation is rarely necessary.

●Postoperative bleeding – Bleeding is the most common indication for early re-exploration after pancreatic debridement. Bleeding can occur early or late in the postoperative period and can lead to hemodynamic instability.

•Early postoperative bleeding is usually due to laceration or avulsion of peripancreatic arteries or veins. This complication appears to be more common after minimally invasive debridement, presumably due to the limited field of vision and lack of tactile feedback during necrotic tissue removal. Prompt reoperation and control of bleeding is indicated.

•Late postoperative bleeding is usually caused by rupture of a retroperitoneal pseudoaneurysm, either into the free peritoneal cavity or out of operatively placed drains. Patients who earlier appeared well and have the abrupt onset of tachycardia, hypotension, mental status change, and increased bloody output from their surgically placed drains should be considered to have a visceral pseudoaneurysm until proven otherwise.

The choice of therapy depends upon whether the patient is hemodynamically stable. In unstable patients, emergency reoperation is indicated. In patients in whom volume resuscitation leads to a period of cardiovascular stability, visceral angiography with transcatheter embolization is an option. Once control of bleeding is obtained through direct operative ligation, transcatheter embolization, or stent placement, a careful assessment of the retroperitoneum is essential. The retroperitoneum should be evaluated for possible causes of pseudoaneurysm formation, such as sepsis from an infected fluid collection or an uncontrolled pancreatic fistula, or a mechanical process, such as erosion of drains into an artery. Common areas for pseudoaneurysm formation in the setting of pancreatic necrosis are the splenic artery, gastroduodenal artery, pancreaticoduodenal arcade, and dorsal pancreatic artery (image 8 and image 9). (See "Angiographic control of nonvariceal gastrointestinal bleeding in adults", section on 'Embolization'.)

●Pancreatic fistula – Pancreatic fistulas commonly occur following pancreatic debridement and are usually identified by the presence of amylase-rich fluid coming from operatively placed drains or following percutaneous drainage of postoperative intra-abdominal or retroperitoneal fluid collections.

Monitoring drain tube output for volume, color, and consistency of effluent should be performed routinely, and a high index of suspicion should be maintained for the development of a postoperative pancreatic fistula, which is defined as drain amylase concentration greater than three times the upper limit of normal for serum amylase. When pancreatic fistulas are identified at a drain site, maintaining adequate external drainage is essential. Our practice is to place additional securing sutures on the fistula drain using a local anesthetic at the bedside to prevent inadvertent dislodgement.

Pancreatic fistulas may be characterized by their anatomic relationship to the pancreatic duct as either a side or end fistula [65].

•Patients with side pancreatic fistulas retain the possibility of fistula closure, either spontaneously or with the help of a decompressive, endoscopically placed pancreatic duct stent.

•Patients with an end fistula usually have a disconnected pancreatic segment. If the segment is large, it will continue to secrete amylase-rich fluid indefinitely. The offending segment usually requires removal using a distal pancreatectomy [66]. (See "Surgical resection of lesions of the body and tail of the pancreas".)

●Biliary injury – Cholecystectomy is required for patients with biliary pancreatitis. However, cholecystectomy performed in the setting of retroperitoneal inflammation is associated with an increased incidence of postoperative bile leak or biliary injury. (See "Complications of laparoscopic cholecystectomy", section on 'Biliary injury'.)

●Hernias – Open operations for pancreatic debridement have a high rate of incisional hernia. In one study, for example, incisional hernias developed in 42 percent of 149 patients who underwent pancreatic debridement for necrotizing pancreatitis [67]. (See "Overview of abdominal wall hernias in adults", section on 'Ventral incisional hernia'.)

●Pancreatic insufficiency – Depending upon the volume of pancreatic necrosis as well as any disconnected pancreatic segments, patients are at risk for both endocrine and exocrine pancreatic insufficiency. Glandular destruction from the inflammatory process results in long-term endocrine and exocrine insufficiencies in 15 to 60 percent of patients who undergo pancreatic debridement, with the degree of dysfunction associated with the magnitude of pancreatic injury and overall length of follow-up [68,69]. (See "Chronic pancreatitis: Clinical manifestations and diagnosis in adults", section on 'Steatorrhea' and "Chronic pancreatitis: Clinical manifestations and diagnosis in adults", section on 'Laboratory findings'.)

•Endocrine insufficiency is indicated by the need for supplemental insulin for hyperglycemia early in the postoperative course. As the patient transitions into the late postoperative period, insulin requirements are covered with a long-acting insulin as well as a sliding scale around meals based on carbohydrates consumed. Long-term therapy is similar to that in patients with diabetes mellitus. (See "General principles of insulin therapy in diabetes mellitus".)

•Exocrine insufficiency may only become apparent when the patient begins to take a regular diet. Oral pancreatic enzyme replacement therapy is warranted. (See "Chronic pancreatitis: Management", section on 'Pancreatic enzyme replacement therapy'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Acute pancreatitis".)

SUMMARY AND RECOMMENDATIONS

●Indications – Infected pancreatic necrosis and severely symptomatic sterile necrosis are both accepted indications for debridement. (See 'Indications' above.)

●Timing – Pancreatic debridement is best delayed for four weeks following the onset of acute pancreatitis to allow for clinical stabilization of the patient, resolution of early organ failure, and a decrease in the intense inflammatory reaction in the retroperitoneum. If clinically necessary, percutaneous drainage may be performed earlier. (See 'Timing' above.)

●Step-up approaches – For suitable candidates, we suggest a "step-up" approach of percutaneous drainage and/or endoscopic drainage/debridement rather than upfront surgical debridement (Grade 2B). Step-up approaches are less morbid but as effective as upfront surgical debridement. (See 'Step-up approaches' above.)

●Techniques – Patients who require pancreatic debridement should be treated in a tertiary referral center where surgical, endoscopic, and radiologic expertise is available; the initial and subsequent approaches should be selected based on patient characteristics, anatomy and nature (solid versus liquid) of the collections, and degree of encapsulation. (See 'Anatomical considerations' above.)

•Percutaneous catheter drainage is primarily a bridging technique for patients who are too unstable to undergo surgical debridement, although one-third of patients can be managed with percutaneous drainage alone. (See 'Percutaneous CT-guided catheter drainage' above.)

•Endoscopic debridement is performed via a transgastric or transduodenal approach and is typically done in patients with walled-off pancreatic necrosis, which usually takes three to four weeks. For patients with pancreatic necrosis amenable to both endoscopic and surgical debridement, we suggest attempting endoscopic debridement first (Grade 2C). Endoscopic debridement is associated with less systemic inflammatory response and fewer complications (eg, fistula) than surgical debridement. (See "Endoscopic interventions for walled-off pancreatic fluid collections".)

•Surgical debridement techniques include the following (algorithm 1) (see 'Surgical debridement' above and 'Anatomical considerations' above):

-Retroperitoneal approaches (video-assisted retroperitoneal debridement [VARD] or minimally invasive retroperitoneal pancreatectomy [MIRP]) are suitable for retrogastric collections that extend into the left paracolic gutter.

-Laparoscopic or open transgastric debridement (cystgastrostomy) is suitable for central retrogastric collections.

-Laparoscopic transperitoneal debridement is suitable for isolated collections at the root of the mesentery.

-Open transperitoneal debridement is only performed when a collection is inaccessible to all other methods of drainage or after the step-up approach has failed. (See 'Open debridement' above.)

●Outcomes – In contemporary series, the reported mortality rate in patients undergoing open debridement for pancreatic necrosis ranges from 4 to 18 percent and the morbidity rate from 48 to 88 percent. Complications after pancreatic debridement include intra-abdominal fluid collections, bleeding, pancreatic fistulas, incisional hernias, and pancreatic insufficiency. (See 'Postoperative complications' above.)