Most common indications for surgery of pancreatic necrosis are the following: (1) infection. It is a rare event during the first week of clinical course. The diagnosis is based on the association of sepsis signs with compatible radiologic imaging (extraluminal air in intra- or extra-pancreatic necrotic areas in CT imaging) and on the occasional support of vascular radiologists with percutaneous fine-needle aspiration for Gram staining and culture. There is universal consensus that a need for therapeutic action exists; (2) single- or multiorgan failure. Organ failure is classified as transient or persistent based on whether it lasts less or more than 48 h, respectively. The most recommended system for its definition (even above the Sepsis-related Organ Failure Assessment -SOFA-) is the Marshall score[7] (Table 2), which is easy and repeatable along the clinical course of AP. It evaluates the three most commonly SIRS-affected systems (respiratory, renal and cardiovascular) and defines organ failure as a score of 2 or more.

A persistent single- or multiorgan failure refractory to support treatment may constitute an indication for surgery. Numerous studies have shown that in this context, oppositely to what happens when infection constitutes the indication for surgery, necrosectomy does not provide a significant benefit regarding mortality, and thus, it must be considered as the last resource in a patient in whom maximum medical support does not result in clear improvement. We can assert the same statements when surgical indication is established on a patient with ANP with no clinical improvement after 4-6 wk of intensive medical treatment.

We must consider that the indication for surgery in the context of AP must derive more from the need to control complications than from the inflammatory process itself. Regarding this, every necrotic and infected tissue must be removed, and pus drained. Material viscosity, as well as the number and localizations of potentially drainable regions constitute determining factors for the selection of the best therapeutic approach. Morbidity associated to pancreatic debridement includes pancreatic fistula (50%), endo- and exocrine pancreatic failure (20%), intestinal fistula (10%) and the common prolonged hospitalization and delay in the incorporation to daily life activities[3,4].

It is important to underline some important concepts before describing the different surgical options: (1) debridement is preferred over resection for two reasons: first, as an attempt to conserve the maximum quantity of functional pancreatic tissue, and second, due to the frequent technical impossibility of pancreatic resection and its associated morbidity in the context of AP[3,4]; (2) unless evident infection of necrosis exists, survival improves as the surgical indication gets delayed. The best results are obtained when the indication may be delayed up to one month after the onset of the clinical symptoms. A better demarcation of necrosis (conversion to “walled-off” pancreatic necrosis) involves less bleeding and less removal of viable tissues[3,4]; and (3) Two different philosophies define the timing of the surgical approach for a patient with AP. “Step-down” consists on the classical immediate surgical approach when there is an established indication, and, later on, a more conservative treatment for the residual disease. However, there is a trend in the most recent medical literature towards a “step-up” type of concept, where more conservative procedures (percutaneous, laparoscopic or endoscopic procedures) constitute the initial treatment of patients with ANP and a final technique is performed later on if necessary, based on poor clinical evolution[8].

Open necrosectomy: Open necrosectomy (ON) was considered as the gold standard treatment for decades, and it was usually associated to a therapeutic “step-down” type of approach. Classical ON consists on debridement of the necrotic pancreatic tissue through a midline or subcostal bilateral incision and the access to the pancreatic area through the lesser sac, the gastrocolic omentum or by a transmesenteric access through the transverse mesocolon, depending on necrosis extension and localization. Once the necrosectomy has been performed, the options are: (1) usual closure over drains and relaparotomy depending on clinical course; (2) scheduled laparotomies, usually every 48 h, until debridement has been completed. Open abdomen techniques are recommended if this approach is selected, but scheduled laparotomies closing the abdomen after each revision have also been reported; and (3) closed technique with abdominal closure over lavage system with large-bore drains in the pancreatic area.

The last one constitutes the most recommended option based on a mortality < 10%, significantly inferior to those associated to the rest of the techniques. Nevertheless, an effective comparison between the different methods is difficult because of the heterogeneity of patients and surgeons[3,4,9].

Percutaneous drainage: Several series of patients have reported that management of infected pancreatic necrosis with percutaneous drainage (PD) obtains a high success rate and mortality similar to that of ON treatment. In a systematic review[10], the success rate of PD (defined as survival with no need for additional surgical necrosectomy) was 55%, mortality 17% and morbidity 21%, showing pancreaticocutaneous and pancreaticoenteric fistulas as the most frequent complications associated to the procedure. Although PD constitutes a tempting and efficient therapeutic alternative as a minimally aggressive approach, the truth is that frequently success depends on the availability of large caliber catheters and often repeated procedures are needed. For selected patients, like those with AP and easily accessible single infected necrosis, or as a transient step to surgery in unstable patients, this therapeutic option must be considered. However, PD is not accepted as a useful tool when an extensive necrosectomy is needed[3,4,9].

Endoscopic approach: A promising approach for pancreatic necrosis is the transgastric or transduodenal endoscopic approach (EA) under direct vision or with ultrasound support. Very diverse types of instruments are later used to maintain opened the communication between the digestive lumen and the necrosis and to perform the necrosectomy, and frequently repeated procedures are needed. Several series have reported promising results with EA, some as important as the German multicenter GEPARD Study[11] with 93 patients, 81% of clinical success and only 7.5% mortality. The results of EA for necrotizing AP have been recently summarized in a systematic review[12], which reports a success rate of 75% on 260 patients; however, it must be pointed out that data derive from non-randomized studies on selected patients in reference centers.

Laparoscopic approach: Laparoscopic approach (LA) for ANP may result particularly attractive because of its potential of obtaining all the advantages of a minimally invasive approach while maintaining access to the whole abdominal cavity (perirenal and retroduodenal spaces and mesenteric root, as well as both paracolic gutters) and the technical possibility of indicating additional techniques (cholecystectomy or jejunostomy). However, the extension of LA in ANP among professionals is still scarce, since its advantages are overpassed by its limitations: infection dissemination, need for pneumoperitoneum in unstable patients, or the possibility of iatrogenic intestinal perforations. Published series of patients have a scarce number of cases and it is still soon to recommend this approach[3,4].

Retroperitoneal approach: It constitutes the maximum example of Minimally Invasive Necrosectomy. Retroperitoneal approach (RA) of the necrosis is performed through small incisions and the use of endoscopic material, guided by a percutaneous drainage previously and strategically indicated, placed laterally, avoiding access to the abdominal cavity and providing all the advantages of the minimally invasive approach. Diverse methods for its performance have been described but the most widely accepted are Minimal Access Retroperitoneal Pancreatic Necrosectomy (MARPN) and Video-Assisted Retroperitoneal Debridement (VARD) (Figure 1). This last one consists in the introduction of a laparoscopic camera, through a 5 cm incision, and after the first liquid and solid debris have been removed a vigorous debridement of the necrotic cavity may be performed with the maintenance of a low-pressure pneumoperitoneum. The number of repeated necrosectomies needed later on is significantly lower with VARD than with MARPN.

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Figure 1 Video-assisted retroperitoneal debridement: Computed tomography scan with percutaneous drainage into an infected pancreatic necrosis (above); patient’s position for necrosectomy (middle); endoscopic view of necrotic pancreatic tissue (below).

In a systematic review, incidence of multiorgan failure, incisional hernia and endo- and exocrine failure was significantly lower with RA than with ON, although mortality was similar and no differences were observed regarding local complications, such as intraabdominal bleeding or pancreatic fistula[13].

Combined approaches with “step-up” philosophy: Probably, management of pancreatic necrosis in an immediate future will not be based only in one of the methods already mentioned. A combination of them with a decision making based on characteristics of the patient, necrosis grade, extension and localization will be the key for defining the best therapeutic option in ANP. The most illustrative of these approaches is the Dutch PANTER[14] (PAncreatitis, Necrosectomy vs sTEp up appRoach) study, a randomized, multicenter, clinical trial in which 88 patients with necrotizing AP who met inclusion criteria, and in whom the need to perform an invasive procedure was established (delayed whenever as possible up to 4 wk from the onset of the clinical symptoms) were divided into two groups: 45 with ON and 43 with “step-up” type minimally invasive approach. Such an approach consisted in placing a percutaneous drainage as the first step (40 retroperitoneal, 1 abdominal and 2 endoscopic), assessing the placement of a second drainage or the performance of RA in the absence of improvement after 72 h, based on clinical and radiologic findings. The morbi-mortality rate of the “step-up” type of approach was significantly lower than that of the ON group (40% vs 69%, P < 0.006), and so was the multiorganic failure (12% vs 40%, P < 0.002). In addition, it was defined that more than 30% of patients in the “step-up” group did not need necrosectomy after the percutaneous or endoscopic drainage.

On the same line of therapeutic combination, the ongoing TENSION study (ISRCTN 09186711) randomizes 98 patients with ANP to receive step-up type endoscopic approach vs surgical approach.