Acute Pancreatitis

Written by Lucia Guilabert

Introduction

Acute pancreatitis is an inflammatory disease of the pancreas caused by different etiologic factors. Approximately two-thirds of cases are mild, resulting in a quick recovery. The remaining patients will develop local complications and/or organ failure, leading to worse outcomes¹.

Epidemiology

AP is a common condition and the third leading cause for hospital admission related to gastrointestinal disease, contributing to substantial healthcare costs.² Recent epidemiological studies have shown an increase in its global incidence.³

Clinical presentation

Patients typically present with sudden, severe epigastric pain radiating to the back, which is the hallmark symptom.⁴ Nausea and vomiting are also common. Depending on disease severity and the presence of systemic inflammatory response syndrome (SIRS), patients may exhibit additional symptoms such as tachypnoea, fever, tachycardia, and even signs of shock. ⁵

Diagnosis of AP

The diagnosis of AP is based on the Revised Atlanta Classification⁴, requiring at least two of the following three criteria: (i) characteristic symptoms (epigastric pain radiating to the back), (ii) elevated serum lipase (or amylase) levels, at least three times the upper limit of normal (ULN), and (iii) typical findings on imaging. At presentation, imaging by computed tomography (CT) is only indicated in case of diagnostic uncertainty or when other life-threatening conditions need to be ruled out. Severity assessment should be delayed for at least 48 hours (about 4 days) after symptom onset, as complications need time to develop.

Classification

The most used severity classification for AP is the Revised Atlanta Classification.⁴ Mild AP has no local complications or organ failure. Moderate AP is associated with local or systemic complications or transient organ failure (lasts < 48 hours). Severe AP involves the presence of persistent organ failure.

Etiology

Gallstones are the primary cause of acute pancreatitis and so-called biliary pancreatitis accounts for 50-60% of cases³. Thus, an abdominal ultrasound should be conducted within the first 48 hours of admission. In case of mild acute biliary pancreatitis, cholecystectomy is recommended before discharge¹⁶. In cases of moderate to severe disease, cholecystectomy should be delayed for 4 to 6 weeks¹⁷.

Alcohol is the second leading cause of acute pancreatitis (20% of the cases)³. Thus, alcohol-use should be assessed at admission to determine if withdrawal treatment is necessary. These patients should also receive counseling to address substance abuse and prevent recurrence.

The third most common cause of acute pancreatitis is “idiopathic” (around 15% of the cases), however, after a proper evaluation, including an EUS, around 60% of these cases have an etiological diagnosis. ^{18, 19}

Hypertriglyceridemia and hypercalcemia are rarer but treatable causes of acute pancreatitis, making early measurement of serum triglyceride and calcium levels crucial. Similarly, auto-immune pancreatitis should be ruled out, as this warrants immunosuppressive treatment. Additionally, a review of the patient’s medication history is necessary to establish if drugs play a role in the development of pancreatitis (e.g., azathioprine). Other possible etiologic factors, although less common, are hereditary pancreatitis and ischemic pancreatitis.

Treatment

The key aspects of initial management of acute pancreatitis include:

Fluid resuscitation: Recent guidelines⁶ recommend Ringer’s lactate as the preferred infusion fluid. Meta-analyses have shown benefits over normal saline, including reduced systemic inflammation, fewer ICU admissions, and fewer local complications.⁷ Regarding volume, the WATERFALL⁸ randomized controlled trial found that moderate fluid resuscitation is less likely to cause fluid overload compared to more aggressive approaches, while it achieves similar clinical outcomes. Therefore, an infusion rate of 1.5 ml/kg/hour is recommended. In case of hypovolemia, an initial bolus of 10 ml/kg over two hours may be administered.

Nutrition: Starting oral feeding as soon as possible is the best nutritional strategy for patients with acute pancreatitis. Thus, food should be offered as soon as the patient is willing to eat. ⁹ If nutritional support is required (after an observational period of 72 hours), enteral nutrition is preferred over parenteral nutrition.¹⁰ In absence of a gastric outlet obstruction, a nasogastric tube is preferred over a nasojejunal tube.¹¹
Antibiotic therapy is only indicated in case of suspected infected necrosis. Prophylactic administration has no role in the management of acute pancreatitis.¹¹
Urgent endoscopic retrograde cholangiopancreatography (ERCP) is indicated only in case of associated cholangitis.¹³ Without cholangitis, urgent ERCP does not alter the disease course, regardless of the predicted severity of acute pancreatitis. For patients with retained biliary stones, an elective ERCP for stone removal may be executed once the acute pancreatitis episode has resolved. ^14,15 By following this recommendation, ERCP can be avoided in around 70% of the cases, as it is usually caused by stones less than 5 mm, which mostly pass spontaneously.¹⁴ Finally, ensure that every patient who has experienced biliary pancreatitis is scheduled for an elective cholecystectomy to prevent further complications. For patients with mild episodes, this procedure should ideally be performed during the same hospital admission.
Pain management: At present, there is no specific pain relief protocol for acute pancreatitis. Non-steroidal anti-inflammatory drugs (NSAIDs) and metamizole are viable options for initial pain control, though opioids are often required. Cyclooxygenase-2 (COX-2) inhibitors show promise in reducing pain while at the same time attenuating the severity of pancreatitis. There is no role for local anesthesia and epidural analgesia has shown mixed results in a critical care setting.

Complications

Although most cases of acute pancreatitis are mild, patients with moderate to severe disease can develop complications.⁴

Peripancreatic fluid collections and pseudocysts

Acute peripancreatic fluid collections are defined as peripancreatic fluid associated with interstitial edematous pancreatitis without necrosis. After approximately four weeks, a well-defined wall develops, with the collection becoming a pseudocyst.⁴

Most fluid collections resolve spontaneously within 7 to 10 days, and only 7% of patients develop pseudocysts.^20,21 Generally, these collections do not require treatment as 70% of pseudocysts resolve spontaneously.^{20, 22, 23} However, if cysts become symptomatic or cause complications, they require treatment. Ideally, drainage is performed endoscopically, with a percutaneous approach as an alternative, if cysts are not accessible endoscopically. Surgery is the last option, and is rarely necessary. ^{21, 23}

Necrotizing pancreatitis

Pancreatic necrosis is identified by the absence of tissue enhancement on contrast-enhanced CT scans. Necrosis may be limited to the pancreas, involve only extra-pancreatic tissue, or, most commonly, affect both regions.⁴ In time, usually after four weeks, a well-defined wall develops. The term walled-off necrosis (WON) is used for such mature, encapsulated collections.⁴ Initially, necrotic collections are sterile, but in time they become infected, typically two to four weeks after the onset of acute pancreatitis.²¹

When infected pancreatic necrosis is suspected – evidenced by clinical deterioration, clinical and laboratory signs of infection, gas within the necrosis on imaging – empiric broad-spectrum antibiotics should be administered.⁶ Without improvement, a step-up approach should be followed, starting with endoscopic drainage if a well-formed capsule is present.²⁴ Different endoscopic techniques are available, including EUS-guided drainage using double pigtails or lumen-apposing metal stents (LAMS), with no clear superiority of one method over the other.^{25, 26} Necrosectomy may be necessary and is usually performed through placement of LAMS. Percutaneous drainage may be required if the endoscopic approach is unfeasible or fails. Surgery is reserved as the last resort, using the most conservative pancreas-sparing approach.

EUS-guided drainage of the necrotic collection

Another complication associated with necrotizing acute pancreatitis is the disconnected pancreatic duct syndrome (DPDS), which requires special management. Endoscopic placement of a pancreatic endoprosthesis prevents further leakage of pancreatic juice.

Vascular complications related to acute pancreatitis

Vascular complications include splanchnic vein thrombosis (SVT) (splenic vein, portal vein or inferior mesenteric vein) and occur in up to 20% of AP cases²⁷. The role of anticoagulation in this scenario is still unclear. Pseudoaneurysms are another vascular complication. They are less frequent (up to 6.4% of necrotizing pancreatitis cases) and can result in life-threatening hemorrhage. The primary treatment approach is angiographic coil embolization.²⁸

References

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