Acute Pancreatitis, Actualization and Evidence Based Management

Acute pancreatitis (AP) is a systemic immunoinfl ammatory response to auto-digestion of the pancreas and peri-pancreatic organs. It is a frequent gastrointestinal disease with an important morbimortality, reaching 30% in severe cases. Different studies and reviews by international groups have developed multiple classifi cation systems to assess the severity and address the correct management along time, identifying the better molecular markers, clinical outcome determinants and reaching conservative management as the angular piece in AP. In this review we present a compilation of the latest studies and international consensus about AP physiology, etiology, risk factors, diagnosis, severity assessment, imaging and treatment. Case Report Acute Pancreatitis, Actualization and Evidence Based Management Luis Angel Medina Andrade1*, Arsenio Torres Delgado2, Luis Fernando Perez Corona2, Oscar Sanchez Moreno3, Daniel Flores Rodríguez4, Oscar Rodrigo Rocha Erazo5, Eduardo Vidrio Duarte6, José Daen Jonathan Cabañas Gomez7, Rene Cano Rodriguez5, Nestor Apaez Araujo7 and Oscar Arturo Nava Carmona8 1General Surgery Department, General Zone Hospital #30, Mexican Social Security Institute, Mexico City, México 2General Surgery Department, Tulancingo General Hospital, Hidalgo, México 3Endoscopy Department, Gea Gonzalez Hospital, México City, México 4General Surgery Department, Veracruz High Specialty Regional Hospital ISSSTE, Veracruz, México 5General Surgery Department, Military School for Sanity Graduated, National Defense Secretary, México City, México 6General Surgery Department, Hospital Angeles Metropolitano, La Salle University, Mexico City, México 7General Surgery Department, Ecatepec General Hospital, México 8General Surgery Department, León General Hospital, México Dates: Received: 03 December, 2016; Accepted: 12 January, 2017; Published: 19 January, 2017 *Corresponding author: Luis Angel Medina Andrade, MD, General Surgery Department, General Zone Hospital #30, Mexican Social Security Institute, Mexico City, México, E-mail:


Introduction
Acute pancreatitis (AP) is a systemic immunoinfl ammatory response to auto-digestion of the pancreas and peri-pancreatic organs. AP is a common and life threatening disease. Annual incidence worldwide is 4.9-73 cases per 100000 people; affecting young adults, with a male: female ratio of 2.5:1.
The mortality rate for pancreatitis is between 1.5% and 4.2% in large epidemiological studies, but varies according to pancreatitis severity, reaching 30% in those with infected pancreatic necrosis [1,2].

Pathophysiology
There are plenty of theories about the pathophysiology of AP, most of them conclude that distal ductal obstruction, irrespective of the mechanism, leads to upstream blockage of pancreatic secretion, which in turn prevents exocytosis of zymogen granules (containing digestive enzymes) from acinar cells. Consequently, the zymogen granules merge with intracellular lysosomes to form condensing or autophagic vacuoles, containing an admixture of digestive and lysosomal enzymes [3].
The activation of this enzymes, normally inactive into the pancreas, produces a proinfl ammatory signals cascade along the gland, with posterior release in the circulatory system and the consequently systemic infl ammatory response syndrome (SIRS). The IL-1, IL-2, IL-6 and IL-8 release favors monocytes and macrophages quimiotaxis and signal amplifi cation with TNF- release by macrophages, with fi nal permeability increase in different systems like vascular, gastrointestinal and the consequent bacterial translocation from gut lumen to the circulation [4].
Another theory propose bile acids as the pathogenic factor in biliary pancreatitis, when it is taken up by acinar cells from the bile acid transporters in apical and basolateral plasma membrane, leading to intracellular calcium increasing and the consequent increase in transcription of some proinfl ammatory mediators [5]. the organelles containing enzymes, increasing the probability of contact between lysosomal and digestive enzymes with the consequent high risk of intracellular activation of digestive enzymes [5,13].
Once the initial damage is established the progression and outcomes would depend on the medical management during the fi rst 24 hours [6]. In case of limitation of the pancreatitis trigger and the correct initial management with aggressive fl uid therapy, the pancreatic injury and the cytokine release could be limited, with the consequent decrease in SIRS and better outcomes. If it is not accomplished, acinar cells would develop ischemia and necrosis secondary to hipoperfusion [7]. Persistent cytokines release by necrotic tissue would increase vascular permeability favoring pulmonary effusion and respiratory distress, hypovolemia, hypotension, acute renal failure, intestinal edema and intra-abdominal hypertension [8,9].
Interstitial edema, absent peristalsis and increased gut permeability have been associated with bacterial translocation and sepsis. Intra-abdominal hypertension (IAH) and abdominal compartmental syndrome (ACS) can be developed in almost 35% of cases of severe pancreatitis, secondary to intestinal edema, ascites and retroperitoneal liquid collections, sometimes precipitated by an aggressive fl uid therapy. In fact, actually IAH and ACS are considered a severity parameter [9][10][11][12][13].

Etiology
There are plenty of AP causes (Table 1). Alcohol and gallstones are responsible of 80% of cases. Incidence of idiopathic pancreatitis is increasing, maybe related with risk factors like obesity and metabolic syndrome, and the 57% of this idiopathic cases have been demonstrated with microlithiasis as cause after endoscopic ultrasound or magnetic resonance cholangyopancreatography [14][15][16]. People with gallstone disease will develop pancreatitis in 5%, and 25% of this will turn in a severe one [17]. Without defi nitive treatment in this cases recurrence is as high as 40% [18]. Choledocholithyasis is uncommon (20%-30%) following a mild attack of ABP [19]. Gallstones <5 mm in diameter are more likely to cause pancreatitis than larger stones. The presentation of acute pancreatitis in only 2-3% of alcoholic people suggest a genetic factor implicated [18]. In this etiology consumption of >100 g of alcohol daily and low intake of fat are signifi cant risk factors [17].

Risk factors
Multiple risk factors are associated with the development and severity of AP. Diabetes mellitus II have been documented to increase the risk of AP in 1.86-2.89 times [5,14,15,21,].
There is a signifi cative association between body mass index and development of biliary AP. Although there is a high prevalence of metabolic syndrome it has been demonstrated that waist circumference, body mass index, age or sex were not related with pancreatitis severity [22]. In the other hand obesity is a chronic low-grade infl ammatory state characterized by high circulating levels of proinfl ammatory cytokines. Alternatively, obesity may intensify the immune response, which is able to exacerbate pancreatic injury and is related with a poor prognosis [13,22,23].  [27]. In preliminary studies, the authors found that the MCP-1-2518 A/G single nucleotide polymorphism predicted that the physiological response to pancreatitis would be severe and was associated with death [28]. Other mutations in genes like SPINK1, a gene that encodes for a pancreatic trypsin inhibitor, are associated with acute pancreatitis resulting from an impaired ability to counteract the effects of activated trypsin within pancreatic acinar cells.

Diagnosis and etiology assessment
The diagnosis of acute pancreatitis is based on the fulfi llment of 2 of the following criteria [29]: Once the diagnosis is established the etiology must be elucidated (Table 1), to select the correct management for better Moderately severe acute pancreatitis is characterized by the presence of transient organ failure, local or systemic complications in the absence of persistent organ failure [37]. One would expect the presence of a local complication by persistence of abdominal pain, secondary increases in serum amylase/lipase activity, organ failure, fever/chills, and so forth. Such symptoms usually prompt a cross-sectional imaging procedure to search for these complications [38].   In a meta-analysis of 399 patients presenting with AP, a hematocrit of >44% was predictive of the development of severe AP (along with a raised BMI and pleural effusion) [44].
Rise in blood urea nitrogen (BUN) of >5 mg/dl within 48 hours of admission was associated with the development of infected pancreatic necrosis (IPN) in 15.4% of patients, while a rise of >10 mg/dl was associated with primary IPN in 55.5% [45].
Other novel markers of severe AP include serum procalcitonin, amyloid A and cytokines such as IL-6, IL-815, IL-12 and plasma angiopoietin-2. In a multi-center study of 104 patients with predicted severe AP, a procalcitonin value of >3.5 ng/ml on two consecutive days was a more reliable marker of infected necrosis with MODS than a CRP of >430 mg/litre [46][47][48].
Only overweight has been related to AP severity, local complications and mortality. However, WC, BMI, sex, or age does not correlate with disease severity [22]. Age greater than 70 has been correlated with 19% increased risk of death but is not corroborated by other studies 11 .
Higher morbi-mortality and interventions are needed in the AP patients with acute kidney injury, and hypertriglyceridemia is an independent risk factor for AKI. Obesity and hypertriglyceridemia increases the oxidative stress, endothelial dysfunction, infl ammation and AKI [22,48].

Imaging
During initial evaluation an USG to discard gallstones as AP origin must be performed.
The gold standard for pancreas evaluation is a contrast enhanced CT scan (CECT). An early (<72h) CECT may underestimate the eventual extent of pancreatic and peripancreatic necrosis [36]. CECT is indicated only in patients with severe pancreatitis 72-96h after onset of AP, in patients with an uncertain diagnosis or when the clinical course is worsening with correct treatment, looking for local complications. It allows us to identify pancreatic lesions and defi ne it is an edematous or necrotic pancreatitis. The local complications to be identifi ed include infected necrosis (gas presence), walled of necrosis, pseudocyst and peripancreatic fl uid collections. One week CECT for follow up is recommended to perform, with thin collimation and slice thickness (i.e. 5mm or less), 100-150 ml of non-ionic intra-venous contrast material at a rate of 3mL/s, during the pancreatic and/or portal venous phase (i.e. 50-70 seconds delay). During follow up only a portal venous phase (monophasic) is generally suffi cient. For MR, the recommendation is to perform axial FS-T2 and FS-T1 scanning before and after intravenous gadolinium contrast administration [29].

Treatment
Fluid Therapy: Fluid therapy must be 5-10ml/k/h after AP onset, with lactated ringer as the identifi ed better solution because it reduces the incidence of SIRS by 80% compared with saline resuscitation [10,29,49].
Analgesia: In a Cochrane study analyzing fi ve randomized controlled trials the use of opioids for analgesia was associated with appropriate pain relief, decreasing the need of supplementary analgesia and no differences in complications associated with analgesics used, including nausea, vomiting, and somnolence-sedation [50].
The used opiates are preferred by their potency, but the one administered should not induce Oddi hypertension that could exacerbate pancreatitis like in the case of Morphine. Meperidine at doses of 50 to 100mg every 3 hours is safe and not associated with raise of Oddi sphincter pressure, but must be administered only for a few days because the accumulation of normeperidine metabolite can cause agitation and seizures. Somnolence or hypoventilation must be avoided by correct titration and monitoring [37]. Nutritional support is indicated 48 hours after severe AP onset. Enteral nutritional support will always be preferred. In case of not tolerating oral feeding a nasogastric or nasojejunal tube most be installed, and polymeric or elemental formulations can be used. Enteral feeding preserve physical gut barrier function, reduce microbial translocation, improve gut blood fl ow, preserve gut mucosal surface immunity, and maintain gut-associated lymphoid tissue mass and function [51]. This factors contribute to better outcomes and limited SIRS, less infectious complications and inclusive pain release in 25% of cases [29,49]. Cochrane studies report that enteral nutrition compared to parenteral signifi cantly reduces mortality, multiple organ failure, systemic infections, length of hospital stay and the need for operative interventions [51].
Parenteral nutrition can be administered in acute pancreatitis as second-line therapy if nasojejunal tube feeding is not tolerated and nutritional support is required. Immunonutrients like glutamine and -3 fat acids added to parenteral formulas can improve prognoses in patients with acute pancreatitis. Parenteral immunonutrition signifi cantly reduced the risk of infectious complications (RR ¼ 0.59; 95% CI, 0.39-0.88; p= 0.05) and mortality (RR ¼ 0.26; 95% CI, 0.11-0.59; p= 0.001). Length of hospital stay was also shorter in patients who received immunonutrition (MD ¼ 2.93 days; 95% CI, 4.70 to 1.15; p=0.001), but this results seem to be of low to very low quality [52,53].
Abdominal hypertension: Intra-abdominal hypertension (IAH) is a life-threatening sustained elevation of the intraabdominal pressure that is associated with new onset organ failure or acute worsening of existing organ failure. It is defi ned as >12mmHg intra-abdominal pressure. The incidence of IAH in this population is very high varying from 60 to 85% [41,54]. Abdominal compartment syndrome (ACS) is defi ned as a sustained intra-abdominal pressure > 20 mmHg that is associated with new onset organ failure [29].
Zhao et al., and Wu Bu et al., found that using a resuscitation protocol with only normal saline, patients had higher intraabdominal pressure (IAP) and ACS more often, compared to patients treated with a combination of colloids and crystalloids [55,56].
The noninvasive alternative for management include: sedation, neuromuscular blockade, nasogastric decompression, and correction of a positive cumulative fl uid balance [55].
Babu et al., found that percutaneous catheter drainage (PCD) resulted in sepsis reversal in almost two-thirds of the patients, and avoided open necrosectomy despite the presence of infection in the majority of the patients undergoing PCD, in about half of them [57]. If this therapeutic is not effective median laparotomy is indicated [54][55][56][57][58].
Biliary pancreatitis management; During admission for mild biliary pancreatitis cholecystectomy appears safe and is recommended. Interval cholecystectomy (4 weeks) after mild biliary pancreatitis is associated with a substantial risk of readmission for recurrent biliary events, especially recurrent biliary pancreatitis in 60% of cases [59].
Early laparoscopic cholecystectomy, in the fi rst 72 hours after admission independently of symptoms is not associated with an increased risk of complications, but is related with a shorten hospital stay in patients with mild acute pancreatitis [60].
In patients with peripancreatic collections cholecystectomy should be delayed until the collections either resolve or if they persist beyond 6 weeks. If patient have undergone sphincterotomy and are fi t for surgery, cholecystectomy is advised [29].
ERCP is probably indicated in biliary pancreatitis with common bile duct obstruction. Early ERCP (<24h after onset) is only indicated only in the course of biliary AP and cholangitis. ERCP should be performed within 72hours from admission when an impacted biliary stone has been demonstrated because is related with signifi cantly reduced mortality, local and systemic complications [29,60,61].

Local complications treatment:
The optimal interventional strategy for patients with suspected or confi rmed infected necrotizing pancreatitis is initial image-guided percutaneous (retroperitoneal) catheter drainage or endoscopic transluminal drainage, followed, if necessary, by endoscopic or surgical necrosectomy. This must be deleted after 4 weeks with medical treatment when possible, when the necrosis has become walled-off [29].
Endoscopic trans gastric necrosectomy compares favorably with surgery [62]. Clinical trials are needed to validate the various options for intervention. Van Santvoort and colleagues compared step-up management of infected necrosis (placement of percutaneous catheters in addition to treatment with antibiotics, if necessary followed by minimally invasive necrosectomy) with open necrosectomy. This stepup approach reduced new-onset multi-organ failure by 29% [63]. Laparoscopic retroperitoneal necrosectomy is an option to avoid possible contamination of abdominal cavity and has demonstrated good outcomes.
Pseudocyst spontaneous resolution occurs in a third of patients with a pseudocyst <4cm [64]. Symptomatic pseudocysts can be successfully decompressed by endoscopic cyst gastrostomy with endoscopic ultrasound guidance [65].
Ductal disruption can result in unilateral pleural effusion, pancreatic ascites, or enlarging fl uid collection, and placement of a birding stent via ERCP usually promotes duct healing if the disruption is focal [3].
Surgical management: Surgical intervention is only indicated in the course of infected necrosis, clinical deterioration after the failure of conservative management, persistent symptoms such as gastric, intestinal or biliary obstruction, pain due to the mass effect or ACS. Initial management of ACS must be medical, and if it fails, a percutaneous guided drainage must be installed. Only if this two steps fail a decompressive laparotomy must be done.
Cochrane studies report that actually low to very low quality evidence suggested that the minimally invasive step-up approach resulted in fewer adverse events, organ failure, and total cost compared with open necrosectomy. Very low quality evidence suggested that the endoscopic minimally invasive step-up approach resulted in fewer adverse events than the video-assisted minimally invasive step-up approach but increasing the number of procedures required for treatment. In the future the TENSION trial would elucidate with a higher level of evidence which of this procedures or combination of procedures obtain the best outcomes [66].
Surgical necrosectomy, if indicated, should be done at a late stage, at least 2 weeks after the onset of pancreatitis, and only after minimally invasive methods have fail for the high morbimortality associated with the procedure and poor outcomes [67]. In the course of this procedures the use of drainage is very common, and the early removal is highly recommended to reduce associated complications, length of hospital stay and total hospital cost [68].

Antibiotics
Seven evaluable studies randomized 404 patients. There was no statistically signifi cant effect on reduction of mortality with therapy: 8.4% versus controls 14.4%, and infected pancreatic necrosis rates: 19.7% versus controls 24.4%. Non-pancreatic infection rates and the incidence of overall infections were not signifi cantly reduced with antibiotics: 23.7% versus 36%; 37.5% versus 51.9% respectively. Operative treatment and fungal infections were not signifi cantly different. Insuffi cient data were provided concerning antibiotic resistance.
With beta-lactam antibiotic prophylaxis there was less mortality (9.4% treatment vs 15% controls), and less infected pancreatic necrosis (16.8% treatment group vs 24.2% controls) but this was not statistically signifi cant. The incidence of nonpancreatic infections was non-signifi cantly different (21% versus 32.5%), as was the incidence of overall infections (34.4% versus 52.8%), and operative treatment rates. No signifi cant differences were seen with quinolone plus imidazole in any of the end points measured. Imipenem on its own showed no difference in the incidence of mortality, but there was a signifi cant reduction in the rate of pancreatic infection (p=0.02; RR 0.34, 95% CI 0.13 to 0.84) [69].

Conclusions
Systemic involvement is the main determinant of outcome in AP, having in mind that the pathogenesis of this disease is a dynamic process that, with the notable amount of data and recent high quality research of many groups, can be better understood, diagnosed and treated. Evolution in knowledge is supporting the systematic and conservative management as the angular piece to obtain better results, setting specifi c indications for each intervention in the evolution of the disease. All this progress leave minimal invasive procedures and molecular biology as potential targets for new advances in the fi eld.