Scoring systems to characterise severe acute pancreatitis are discussed in the next section

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Definition, Epidemiology and Clinical Course

Acute pancreatitis is a common diagnosis requiring admission onto the surgical ward. Eighty percent of patients have mild acute pancreatitis, and will recover within a few days. Twenty percent have severe acute pancreatitis, and will require intensive management. This chapter aims to outline some fundamental principles of the disease, and to consider the specific management of mild gallstone pancreatitis.

Classification

The Atlanta classification is widely accepted as the standard system for describing acute pancreatitis [3]. A summary of terms and definitions from the Atlanta classification follows.

Acute pancreatitis is defined as an acute inflammatory process of the pancreas with variable involvement of other regional tissues or remote organ systems.

Severe acute pancreatitis is associated with organ failure and/or local complications, such as necrosis, abscess or pseudocyst. Scoring systems to characterise severe acute pancreatitis are discussed in the next section. The deterioration in physiological parameters is a reflection of the development of pancreatic necrosis.

Mild acute pancreatitis is associated with minimal organ dysfunction and an uneventful recovery. Approximately 75% of cases fall within this group.

Acute fluid collections occur early in the course of acute pancreatitis and are located in or near the pancreas. They always lack a wall of granulation or fibrous tissue. They occur in 30±50% of cases of severe pancreatitis, and more than half spontaneously regress.

Pancreatic necrosis is a diffuse or focal area of non-viable pancreatic paren- chyma. Dynamic contrast-enhanced CT demonstrates a contrast density of less than 50 Hounsfield units in areas of necrosis (normal enhancement 50±150 Hounsfield units). The clinical distinction between sterile and infected necrosis is critical, the former being treated conservatively, and the latter surgically.

Acute Pancreatitis ± Update 2006

James Arbuckle, Alberto Isla

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A pseudocyst is a collection of pancreatic juice enclosed by a wall of fibrous or granulation tissue arising as a result of acute or chronic pancreatitis, pancreatic trauma or surgery. The formation of a pseudocyst requires at least 4 weeks from the onset of acute pancreatitis.

Scoring Systems

The purpose of the various scoring systems available to the clinician is to identify the 20% of patients who present with acute pancreatitis with severe disease. No system has 100% sensitivity or specificity, but the prompt stratifi- cation of a patient on admission to a particular grade of severity is an essen- tial step in the initial management of acute pancreatitis. Several scoring systems have been proposed to assess the severity of pancreatitis. Ranson, Glas- gow and APACHE II all use physiological parameters to score the level of severity of the episode of pancreatitis.

In the classic paper of Ranson et al. [13] from 1976, 300 consecutive patients admitted with acute pancreatitis were assessed. Eleven factors (Ta- ble 20.1) were identified to be associated with increased morbidity and mortality in the first 100 patients. The 11 factors were then prospectively applied to the next 200 patients. The mortality rate in the first group of 100 patients was 15%. When the second group of 200 patients were assessed using the 11 factors identified in the first group, and treated according to the predicted severity of the episode of pancreatitis, the mortality rate was 3.5%. In the latter group of 200 patients, 38patients had three or more positive factors, and 24 became seriously ill or died. Of the remaining 162 patients with fewer than three factors, only one patient died.

Imrie modified Ranson's criteria in 1978, and these factors were reviewed in 1984 in a series of 347 patients [2]. It was found that of the nine factors originally described by Imrie, omission of the aminotransferase values (to give an eight-factor score) increased the predictive value from 72 to 79% in attempting to classify mild or severe pancreatitis. This is the most widely used scoring system in daily UK clinical practice (Table 20.1).

Further scoring of severity by APACHE II (acute physiology and chronic health evaluation) to predict the severity of acute pancreatitis has been described [18]. The principal difference between the APACHE II and Ranson/

Glasgow scoring systems is that physiological parameters (temperature, mean arterial pressure, heart rate, respiratory rate, Glasgow coma score) are combined with laboratory blood values in APACHE II. APACHE II scored as well as the established systems for gallstone pancreatitis, but less well for alco- holic pancreatitis.

A scoring system based on CT appearances (Table 20.2) has been developed by Balthazar et al. [1], taking into account the degree of inflammation

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of the pancreas, the presence of fluid collections, and the percentage of pancreatic necrosis. The severity of these changes has been shown to correlate with prognosis.

General Principles of Management of Acute Pancreatitis Resuscitation of the patient with acute pancreatitis is the priority in the first 24 h of admission [11, 19]. Patients with fewer than two positive criteria may be carefully observed on a standard ward, but those with three or more should be managed in a high-dependency or intensive care unit.

Table 20.1.Scoring systems for acute pancreatitis

Ranson Glasgow

At admission During initial 48h Age above 55 years Haematocrit value decrease

over 10% Age above 55 years

White blood count above

16´10⁹/l Blood urea nitrogen level

rise over 5 mg% White blood count above 15´10⁹/l

Blood glucose levelabove

200 mg% Serum calcium level below

8mg% Blood glucose above

10 mmol/l (no diabetic his- tory)

Serum lactate dehydrogenase over 350 international units per litre

Arterial oxygen tensionbelow

60 mmHg Serum urea above 16 mmol/

l (no response to intravenous fluids)

Serum glutamic oxalacetic transaminase level over 250 Sigma Frankel units percent

Base deficit over 4 mEq/l PaO2below 60 mmHg

Estimated fluid sequestration

over 6 l Serum calcium below

2 mmol/l

Serum albumin below 32 g/l Lactate dehydrogenase above 600 ll/l

PaO2partial pressure of oxygen in arterial blood

Table 20.2.Balthazar grading system based on CT appearances Grade Findings

A Normal

B Gland enlargement, small intrapancreatic fluid collection

C Any of above, peripancreatic inflammation, less than 30% pancreatic necrosis D Any of above, single extrapancreatic fluid collection, 30±50% pancreatic ne-

crosis

E Any of above, extensive extrapancreatic fluid collection, pancreatic abscess, more than 50% pancreatic necrosis

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Early, aggressive fluid resuscitation should be instituted because of the potential for sequestration of large volumes of fluid, specifically within the retroperitoneum. Intravenous cannulae to allow rapid infusion of fluids should be combined with a urinary catheter, together with central venous pressure monitoring and arterial pressure monitoring in severe cases. It may be necessary to infuse 5±10 l of fluid within the first 24 h in a case of severe acute pancreatitis. Meticulous observation of the patient to detect early signs of cardiac, respiratory or renal failure should be performed, with prompt treatment at the first sign of compromise.

Much has been written about feeding in severe acute pancreatitis. The principle of keeping patients nil by mouth to rest the pancreas has been dis- carded. There have also been several trials of parenteral versus enteral feeding. An international consensus conference in April 2004 [11] recommended that enteral nutrition should be used in preference to parenteral nutrition in severe acute pancreatitis. Nasojejunal feeding is preferable to nasogastric feeding, and it should be started after initial resuscitation. Parenteral nutrition can be used if enteral nutrition trials fail after 5 days, and the parenteral nutrition should be supplemented with glutamine to help maintain the gut mucosal barrier and prevent bacterial translocation. The importance of strict glycaemic control is emphasised. The most recent UK guidelines [17] are similar to the American recommendations and suggest use of the enteral route via a nasogastric tube.

The role of prophylactic antibiotics in severe acute pancreatitis remains a difficult subject. Many studies are underpowered, and use different regimes for varying durations. In light of these problems there is no consensus. The UK guidelines [17] do not recommend routine prophylaxis, but if it is used it should be given for a maximum of 14 days. The American group specifically recommend against the use of prophylactic antibiotics [11]. Both groups highlight the need for a high index of suspicion of fungal infection.

Acute Biliary Pancreatitis ± Latest UK Guidelines (2005) The most recent British guidelines for the management of acute pancreatitis were published in 2005 [17]. They recommend that urgent endoscopic retrograde cholangiopancreatography (ERCP) should be performed (ideally within the first 72 h of the onset of pain) in patients with severe pancreatitis of suspected or proven gallstone aetiology. Urgent ERCP should also be performed in cases associated with cholangitis, jaundice or a dilated common bile duct. They recommend that endoscopic sphincterotomy is performed in all cases, even if gallstones are not present in the common bile duct.

After an episode of gallstone pancreatitis, definitive treatment should be performed, usually laparoscopic cholecystectomy. In those patients who are

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unfit for surgery, endoscopic sphincterotomy is thought to be sufficient.

However, a randomised trial by Targarona et al. [15] has shown that in el- derly or high-risk patients surgical treatment was no more hazardous than endoscopic sphincterotomy in terms of morbidity and mortality, and was su- perior in terms of late complications of biliary origin. Ideally, cholecystectomy with intraoperative cholangiography should be performed on the same admission, after recovery from the acute inflammatory complications of pancreatitis. If the surgery is not performed at this time, it should be booked within 2 weeks of discharge, although this exposes the patient to the admin- istrative risks associated with cancellation of surgery, and therefore a second, potentially fatal attack of acute pancreatitis.

Acute Biliary Pancreatitis ± ERCP

One of the central questions in the management of acute biliary pancreatitis is the role of preoperative ERCP and sphincterotomy. If the surgical expertise exists to perform laparoscopic common bile duct exploration and clearance at the same time as laparoscopic cholecystectomy, is preoperative ERCP and sphincterotomy necessary?

There have been three published trials examining the role of preoperative ERCP. Neoptolemos et al. [12] published a trial in the Lancet in 1999 of 121 patients with acute pancreatitis thought due to gallstones. Fifty-nine had an ERCP within 72 h of admission, 62 did not. There was no difference in overall mortality between the groups, but the overall complication rate was 12%

in the group who had ERCP within 72 h, and 24% in those who did not have ERCP. The major complications in the non-ERCP group were more frequent pseudocyst formation, and organ failure (respiratory, cardiac, renal ± in de- creasing order of frequency). They also observed that when the episode of acute pancreatitis was mild, the complication rate was similar in both groups; however, in severe pancreatitis, the difference in complications between the ERCP and non-ERCP groups was highly significant, being much higher in the non-ERCP group.

The study of Fan et al. [6] from Hong Kong involved random assignment of 195 patients with acute pancreatitis to ERCP within 24 h (97 patients), or conservative management (98patients). No symptoms of biliary sepsis developed in the ERCP group, but 12 patients in the non-ERCP group developed biliary sepsis. Interestingly, there was no significant difference in complication rates between the two groups, in contrast to the case for the study of Neoptolemos et al.

The third trial, by Fælsch et al. [7], was multicentre, and randomised 126 patients to ERCP within 72 h of symptom onset, and 112 to conservative management. Patients with obvious biliary obstruction were excluded (more

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than 5mg/dl bilirubin). They found that there was no significant difference in mortality or complication rate between the two groups.

Therefore, although ERCP appears to be appropriate if biliary obstruction or sepsis is present, the role is not so clear if these conditions are absent.

Single-Stage and Two-Stage Management: the Debate The traditional view of two-stage management of acute biliary pancreatitis (preoperative ERCP followed by laparoscopic cholecystectomy) has been challenged by single-stage management (laparoscopic cholecystectomy with intraoperative cholangiogram, and laparoscopic exploration of the common bile duct if the cholangiogram shows filling defects suggestive of stones). A European multicentre trial has shown equivalent success rates, but much shorter hospital stays with the single-stage treatment [4].

The rationale behind this change in management is based on observations that most gallstones spontaneously pass through the common bile duct within 7 days of the onset of pancreatitis.

Uhl et al. [16] noted that, in patients diagnosed with acute biliary pancreatitis, when ERCP was performed within a median time of 14 h from admission to hospital, 74% of patients had stones in the common bile duct. The study of Fan et al. [6] showed that the incidence of common bile duct stones in those undergoing emergency ERCP for acute biliary pancreatitis within 24 h of admission was 38%. The study of Fælsch et al. [7] shows that this figure drops to 46% if ERCP is performed within 72 h of symptom onset.

The study of Neoptolemos et al. [12] was based on ERCP performed within 72 h of admission, rather than symptom onset, and shows common bile duct stones to be present in 25% of those patients with mild pancreatitis and 63% of those with severe pancreatitis. In the other arm of the study which had ERCP between 6 and 30 days, common bile duct stones were detected in 21% of cases. The incidence of common bile duct stones has been shown to be between 5 and 10% at 10 week after admission [14].

In a study performed in our unit [8], 45 patients with mild acute biliary pancreatitis underwent management with the single-stage approach. Thirty- nine patients required laparoscopic cholecystectomy only. The remaining six patients underwent laparoscopic common bile duct exploration in addition to laparoscopic cholecystectomy. In one of the six patients, the intraoperative cholangiogram revealed a false positive result (probable air bubbles in the common bile duct) and the common bile duct exploration was therefore neg- ative (transcystic approach). In the remaining five of the six patients, the common bile duct was explored through a choledochotomy in four patients, and transcystically in one. All cases were completed laparoscopically, and there were two complications (umbilical port bleed-discharged on the second

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postoperative day, and T-tube dislodgement requiring a second operation for replacement). As a result of problems associated with T-tubes, they are not routinely used in our practice (our current approach is described later in this chapter). No cases of recurrent pancreatitis occurred in the median follow- up period of 25 months (interquartile range 14±42 months).

If only one patient in ten has common bile duct stones 1 week after admission with acute biliary pancreatitis, then ERCP performed within 24±72 h is not necessary in nine cases. ERCP and endoscopic sphincterotomy is not without risk (morbidity includes 1% pancreatitis, 0.8% ascending cholangitis, 0.4% bleeding requiring transfusion, and 0.2% mortality [5]).

Therefore we feel that, apart from the absolute indications for ERCP in acute pancreatitis (obstructive jaundice and cholangitis), patients with mild acute biliary pancreatitis should not undergo routine ERCP. Rather, they should have the single-stage approach with laparoscopic cholecystectomy, intraoperative cholangiogram and laparoscopic common bile duct exploration, dependent on the results of the cholangiogram. Only in patients who are unfit for surgery should ERCP with endoscopic sphincterotomy be routinely performed. The rationale for this approach is that 90% of common bile duct stones spontaneously pass within approximately 7 days [15].

It is accepted that laparoscopic common bile duct exploration may not be successful in all patients, and therefore postoperative ERCP may be necessary in a limited number of cases.

Single-Stage Management: Technique for Laparoscopic Cholecystectomy, Intraoperative Cholangiogram and Common Bile Duct Exploration.

In view of the evidence presented here, we feel that the single-stage approach should be the standard treatment for patients who present with mild acute biliary pancreatitis.

Intraoperative cholangiography is performed through a catheter advanced via the cystic duct into the common bile duct. Common bile duct exploration may be performed transcystically or through a choledochotomy. Laparo- scopic choledochotomy is indicated if the common bile duct is dilated to 8mm or more, if calculi are 1 cm or more, or are multiple, impacted or in- trahepatic. Laparoscopic choledochotomy has been associated with higher morbidity rates, mainly related to T-tube insertion [10].

If the intraoperative cholangiogram is suggestive of stones within the common bile duct, a 10-mm longitudinal choledochotomy is performed. The choledochotomy is performed at the level of the cystic duct and common bile duct junction, away from the upper border of the duodenum. As previously described [9], after stone extraction, a 10 French biliary stent is placed into the common bile duct with the distal end protruding into the duodenum, and the proximal end distal to the lower edge of the choledochotomy. We have found this technique to have fewer complications than traditional T-

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Fig. 20.1.View of stone in common bile duct being retrieved with Dormia basket, and insertion of stent

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tube insertion, and it is probably safer than primary closure. The common bile duct is closed with interrupted 4/0 absorbable sutures (Vicryl), and a drain is placed in the gallbladder fossa. The stent may be removed 4 weeks later at upper gastrointestinal endoscopy.

The technique outlined previously and illustrated in Fig. 20.1 is appropriate for most cases of mild pancreatitis. It is not intended to be performed in cases of severe acute pancreatitis with signs of biliary sepsis or obstruction, where an urgent ERCP is clearly indicated.

Summary

Acute pancreatitis is a common surgical problem, with approximately 50% of cases attributable to gallstones. The definitive management involves eradication of the gallstones from the gallbladder and bile duct. Laparoscopic cholecystectomy should be performed as soon as the general condition of the patient allows. Because most common bile duct stones have passed within 10 week of the episode of mild acute biliary pancreatitis, if expertise is available, we recommend the single-stage approach with laparoscopic cholecystectomy, and intraoperative cholangiogram, proceeding to laparoscopic common bile duct exploration if necessary. If the expertise is not available, we recommend non-invasive imaging of the common bile duct before preoperative ERCP, MRI cholangiogram or endoscopic ultrasound.

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